Working on this same amp (combo) and thanks so much for explaining the tube swap voltage test. Just tested it and the values carried over when I swapped the tubes. Screen recorded this to have it in my back pocket. You’re the best Brad!!!!!
Man I just can't get over how valuable these videos are. I have an MTS Carvin... Well gave it to my old girlfriend and thus don't have any tube amps anymore but these videos are my type of TV. Always learn something. Every time.
I bought a JCM 2000 used and after a week or so it developed a similar problem. Sent it in for repair and it came back sounding great. That was 5 years ago and it's still going strong with no problems. Love that amp.
I've bought one from a customer for £50 , as the solution to the runaway bias from the conductive pcb is a new board from Marshall , £125 , I think was the price . Plus labour , not cost effective for him . But eventually I'll modify the old board with the "Dr Tube" drill and mod method . I think I paid £60 for the kit .
This is so weird- my jcm2000 DSL100 is following the same exact issues in the same order as this one. You're saving me a yit load of troubleshooting time. Thanks!
Brad, I was trained by the Navy as an avionics tech, back in 1970, and used to enjoy tinkering with tube amps (as a bass player since 1967). This video, however, has convinced me beyond all doubt that I never want to see the insides of one of these newer monsters!! God bless your patience, persistence, and curiosity! LOL You're a better man than I, McGee! LOL Is your piece of trash a fuse?
I owe you some dough because I had to put in a new JCM2-60-00 Revision 20 board in and you helped me with that. Thanks to you, I also bias'd it. It was WAY off. If you have a paypal or another method, I'll send you $50 because you saved me at least $200 so far. Thanks and I hope you all are staying safe. Great videos.
Man i had a TSL 100 that would run away. Id send it to my guy hed bias it then give it back and it would do it again. After about 3 sets of tubes i did some checking and found bias resistors that woukd thermal reactive. They would change value with a hair dryer on them. Finally got a new main board and the problem went away. Funny thing all thise suspucious resistors were changed to better ones. I hate engineer bean counters. Now i play a metro and a matchless. No more pcb for me. Keep on keepin on.
Question: how do I send my DSL to you because honestly I have no interest in knowing the secret voodoo that you know that fixes these! I am hoping you still do repairs!
Hahaha bro! Yes, my amp guy just keeps saying, “just bring it back it’s no biggie”. A week later it goes out and he says, “just bring it back no biggie”. 🤣
Kudos to you sir. You know your stuff! I blew my amp the other night. Same one you have here (JCM2000 DSL 100 watt into a 1960 dsl900 4x12 cab). I was playing on "2" for about an hour when my other guitarist decided to crank it at practice. I got tired of him blowing us all out, so I turned the amp up on 10. Struck one chord and... crickets. Used my backup fender amp to finish practice. Now looking further into my prob, I see that an EL34 has blown. Looking from the back of the amp, it is the left outermost tube. I also blew the D198 250 VA fuse. No smell in the amp so I hope I didn't blow anything else. Didn't make note when I unplugged everything (it was late) but I believe I mistakenly had the cab plugged into the 8 ohm output on the amp. :( It played for an hour, so, I'm not sure if the ohm mismatch blew it or not. But if it did, where else would I have issues? Also, where can I get another D198 fuse? Thanks so much for any help you can give!
If you ever found the answers to your questions, PLEASE LMK! I am fairly certain that my ORIGINAL prob (way back) was accidentally playing through mismatched cans. Now I just re-tubed, & blew HT fuse. I've got a lot of digging & video watching & I'm dying to get back into playing now! (Plus been working 6-7 nights/ week lately... I know, I'm pitiful... all help much appreciated!
Thanks for this video Brad, this was really interesting. Blew my mind when that particular cap measured so bad. Lots of plugs and wires to disconnect and mislabeled schematics from the factory, that’s kind of an automatic handicap right? This was cool 😎 as usual, you rock.
Why do you suppose they would have put so freaking many connectors and plugs in? Just because it was easier to pay someone to build the parts piecemeal and then pay someone to finally wire it up? I bet that was it, to save a tiny bit of the almighty dollar. Oh, I forgot, save to pound. Pound sand I say...
@@TheGuitologist I just found & subscribed to your site about a week ago. I picked this video (hoping for a bit more advice & I'm on a time frame) but I've got an '04 TSL 100 & just getting back into playing after a few years off (& DYING to hear that Marshall & 1 of my Explorers) so I re-tubed last night before work. I had been playing it last week when I noticed the 1st power tube was just shot, dead. Anyway, it made a little sound before I killed the Output Mute & then V.P.R. buttons, then blew HT fuse. All tubes were still lit. I do factory automation/ maint & WILL soak up much from your experiences. I appreciate you doing what you do & helping others. I guess 1st question... I was sold 4-ECC83 S's for the pre-amp. HOWEVER, the original Marshall tube was still in the far left position w/the can/shield on it w/the nomenclature VLVE00064 WK43 on it. Do I need to go BACK to the music store and get a different tube or will the ECC83 S be ok there??? Looks like I'll be watching videos all day and possibly weekend and pray hard & often! Terrible timing w/just getting my FIRE RELIT. 1 last thing. I brought home a 5pk of Buss GMC-1-R fuses for T-shooting my issues. I'm guessing from what I've been learning, that's not a good idea...? Do I really have to go find some F1A L250V fuses for my t-shooting? Thanks for ANY help & I WILL be buying some swag asap!
Bad layout, what a waste of a PCB I see this too often with modern amps they design them to be throw away BTW that wire you mention isn't dark purple but Deep Purple
Mate ! , I was waiting for you to find an intermittent short on/in, a power tube .. I shelled out for a tube tester to eliminate faulty tube dramas at 1st base.. I read up on tube control Bias a lot lately , and i find the current sensing resistor , is there not only to reference milliamps to millivolts , but it is also to protect the control grid like a fuse would .. which is why you only should use just a half watt , 1 ohm type . (of course if you use 10 ohm , it would show 10 mV for 1 mA). When i build a fixed bias amp, i make sure i have available, as a bias voltage , at least 10 % of the plate voltage , at the middle of the bias pot travel . so if the amp idling( all volumes and eq turned down to 0), has a plate voltage of say 480 dc volt ,, i want -48 v on the centre of the bias pots travel .and i want to be able to adjust that by 25% each way at least . There could be a problem in your bias voltage supply .. crap filter cap , resistor ,, and make sure you have a decent negative voltage on the control grid . Pin 5 on that octal tube.. Over here in Australia , the amp companies built large amps with insufficient bias control , and the same with heater current . i had an amp built here that had 6 of EL 34 and 3 of 12 ax7's , and the heater winding for the power tubes was only good for 6 amps, which is why it chewed through tubes , stripped the damn cathodes ! when the fault takes out the current sensing resistor , its preety much saving the output transformer from dying ! Cheers Brad ,, love your work ..
Love the channel Brad, I'm a first year Electrical Engineering student in Canada, and you really inspire me. How would you go about learning more about tubes and amplifier circuits? We dont cover Tubes or anything like that in any of my classes and this is the industry I want to work in. Thanks again, Anthony
First, buy and read these books: amzn.to/2FFGyWa amzn.to/2FKXMBq amzn.to/2FGnGX8 Watch ALL of Uncle Doug's videos. Then come back and watch all of my videos. Then watch all of D-Lab's videos. Drop out of school. Piss parents off. Be happy. :D
May i add: DeepBlueHarp, ElPasoTubeAmps, Joernone and, of course, Dennis Carter and Mr. Carlson´s Lab and be and stay curious, do DIY from scratch and if anyone say "not possible" Do it...it´s a ton ´o´fun...(DrehKoPhaser, AllTubeSynth) And repeat these three by heart (and for sure at 02:17AM when interrupted from sleep): R=V/I, P=V*I and f=1/T=1/(2*pi*C*R) there´s nothing more to know...you can go through pretty much anything tube related using just these three, of course, you would need to know them inside out and: by heart and it must be a pleasure for you to juggling around with them letters, by head not on paper;) Buy: The Art Of Electronics, all RCA tube manuals (at least see them once 1:1 in a library if you downloaded them as PDFs) And learn to solder with both hands in equality...;)
Sorry Brad, I think you missed this one and this amp will be coming back. A power supply cap can't burn out the cathode resistor or cause that tube flash. Assuming that tube still works, I think that tube is shorting. That's about the only thing I can think of that would cause that flash. If the tube is now dead, then there was excess current though the tube and it burned out a wire inside. But if loss of bias can't do that, then it suggests a internal short. It happens. That why tube checkers have tests for shorts.
That cap is in the HT line. It was the only bad component on the entire HT I found that was bad. Granted, I didn't go all the way into the preamp, but I did check all the solder joints in the preamp. I think it was that cap. It would be a very unique problem if a power tube was shorting one second and fine the next.
I could see the cap blowing the fuse, but not the tube flash. Yes, an intermittent tube would be unusual, but not impossible. Intermittents are always a %&#$. If you correspond with the other guys like Uncle Doug or D-Lab, you might want to run this by them.
If there was a high voltage spike because that cap was misbehaving though, it could cause a tube spark. At least it makes sense that it could in my mind. As for Uncle Doug, I don't think he ventures much into modern amps. Terry at D-Lab may, but I don't know what he could tell me that I haven't already tried. I've read a lot of forum posts where techs are advising some to up the value of that HT fuse slightly to avoid problematic fuses, and I do agree that like a 1.5A fuse probably wouldn't hurt a thing, and may prevent some fuse blowing due to transients. But I think the issue with this one was that cap at first, which took out the R9. Then my shoddy speaker connection likely caused the later fuse blow. I played the amp for a long time after that and no issues. But yeah, intermittents are a pain in the ASS.
Time will tell. All I can say is my "tech sense" is still tingling. It won't give me a "warm fuzzy". But I understand the situation. If you can't recreate it, at some point you have to send it back to the customer. The only thing I can suggest is to make sure you test it with it sitting on the speaker cabinet so gets vibrated.
I totally hear you. I didn't get "that warm fuzzy feeling" either on this one. More like I had to jump out of bed and out the window putting my boots on. FWIW, I spent a good while I didn't put in the final video chopsticking with the amp on, and I played it and burned in a good long time. Like you said, the ghost won't show itself, maybe it went away?
Thank you for posting this!! Could this the be cause of my sick DSL? I can't wait to find out! Geez, much cheaper than replacing the socket PCB... that I already spent money on :( Marshall doesn't include those plastic stand-offs with the new board and repurposing the orginals barely works :( Not even sure where I can get new ones. I need some!
Love these videos, I don't even own a marshall I just like seeing things being traced and fixed, we're all nerds I guess, keep up the good videos! Now everybody with a 2005 with same symptoms can learn what's going on with it, :D
I had one of these. Same problem and it ended up burning the board. Something to do with the PCB design and traces of the earlier ones. Amp tech bypassed those traces by hand wiring that part of the circuit. He called it 'lifting'.
PLEASE HELP ME SIR! I have a BIG PROBLEM WITH MY AMPLIFIER! I TRIED 1 WEEK TO SOLVE THE PROBLEM SO I NEED YOUR HELPP 🥺🥺🥺 I have a Turkish Marshall 1987 x amplifier clone from 70s. No matter how I try to fix, the inner power tube red plates whenever I play my guitar. Even though I changed the tube’s locations, the problem still continues. So I came up with that tubes do not have a problem but socket does. I even change the phase inventor coupling capacitors. I measure the colts in the grids of power tubes and it was -40 volt which was a suitable number. One of the screen resistors of the other non problematic tube was blown and I have changed it in case there was an imbalance but nothing changed.
Check for bias on the grid of the power tube that red plates, there should be somewhere around negative 26 Volts, on that grid, and the same as all the other grids. You can take the tube out (take all tubes out) and measure the negative volts on the the grids (at the pin for grid itself), they should all be the same and close to 26 volts for the 1987 Marshall with EL34's. If it is lower, then repair the bias supply, which is , a diode, filter cap, and a few resistors, could also be You have to retension that tube socket sleeve, because it is not making good contact with the tubes grid pin.
How many times did you say mother F er when you were working on it? This should have been called the nightmare of all Marshall amp repair videos. You have much more patience than I do. :-)
just replace the board with a rev. 20 cures everything !!!!!!!!!!!!!!!!!` I isolated tube pin on all power tubes and jump a wire V8 5 pin too R10 resistor ,, v7 5 pin to R resistor . V6 too resistor and v5 too R7 resistor that cures bias runaway as temporary solution till I received the new Revision board but the Green board itself is very unstable too extreme heat ,, the Version 20 board solved all the issues $200 for new board well worth it these are by far the best sounding Marshalls I have the TSL 100 version .. The amp your are working on the version 7 board could have caused all the other issues also
JJ tubes are GARBAGE!! just had the same problem. Replaced tubes.. Also, 1 ohm resisters...and the bias feed R77 I think..should be 3.9K..on that one, it might be 10K.. put a 3.9k in there..make sure the 220k gets back down to 5.6k.. and I PROMISE IT WILL BIAS... also Marshall is full of shit.. DO NOT BIAS THAT TO 90! bias it up to 78 and itll be great!
in case you didn´t know: JJ is the only (!!) large number tube producer left in the western world. They do tubes for nearly all vendors, regardless what´s stamped on. All tubes around here are made by JJ, or they´re made in russia (=C=, svetlana(origin), electro harmonics (brand),RCA (brand), TungSol(brand), simply check tubes.ru for other brands you used to know. I visited the saratov plant years ago, before they went by the "NewSensor" name they done tubes and they still do tubes) and china (they even use TESLA nowadays,RCA,amperex,WE and other formally well known tube brands)
I have a 2002 Marshall JCM 2000 DSL 100. It had the bias drift problem. A few minutes with a Dremel and four new grid resistors for the power tubes and the problem is solved. Bias is rock solid. Touched up the solder joints on the bias adjust board while I was in there since that's a common failure mode (cracked solder joints). The amp plays great now and runs very stable. These amps get a deservedly bad rap for poor engineering of the main board but it's an easy fix and you end up with a great amp that rocks.
90mv is 45ma per tube - hot! Those pots are highly interactive. I was thinking that they adjust the tubes on the opposite side. C46 has a tendency to blow short. You are lucky that you didn't have the dreaded conductive PCB issue, which requires some work with a Dremel. Thanks for the tip on those caps.
I thought when he said 90 in the video it was awfully damn high. Those resistors likely fried whenever you cranked the hell out of it trying to get it set to 90. 30 is on the cool side and 45 would be hot as a firecracker with a set of your favorite humbuckers. The bias on mine was just set between 33 and 35 if I'm not mistaken.
Brad, I have fixed the Thermal Runaway issue with these amps. The circuit board material becomes conductive over time and then the tubes loose bias and then runaway. I isolate pin 3 of all the power tubes from the board by cleaning around the pin with a dremel. Then a jumper wire is installed to complete the circuit that you have cut.
I sat through it 4 no reason. Lol I own a Marshall class5 head on am egnater cab. But iv been binge watching Brad for the last 3 weeks now. Its guitar porn..lol keep up the great work there Brad
Yeah Brad it's a nifty looking little tester & I might build one for myself. But I wouldn't trust it for one second with leaky caps to be honest. Use your multimeter for that! Or better still, I was gonna look into the capacitor leakage tester that Paul at Mr. Carlsons Lab designed. Looks like a fantastic device & the most sensitive I've ever seen! It can measure leakage through insulated wires! His design is apparently on Patreon. I'm gonna make myself one, & you probly should too! Make a video of it if it's ok with Paul. I'd definitely watch it.
The winner of the "identify the trash on my sidewalk" contest is John Anti! Congrats, John! You correctly identified that little piece of metal as one of the switch contacts from a 3PDT switch. It was, in fact, the missing contact from this video: ua-cam.com/video/OCdYNq6fYTI/v-deo.html Email me at bradlinzy at gmail to claim your prize. If John doesn't email within 24 hours, I'll choose another winner from the correct answers.
Love your vids... to think my first amp for Bass was a Linear Concord HiFi Amp all Valve back in 1962...then Selmer Treble n Bass 50watt heads & Selmer Goliath/David Cabs 3x Heads with 3x18 Cabs - proper music gear.... now about my 100watt Seymour Duncan 'Convertible' Amp - got it back in 1988-9 hardly ever been turned on and only in Studio setting... Guitar & Bass eh! tricky decisions. Thanks for Posting truly amazing and love the guitar playing. Michael @OAK77uk Tweetland/FB
It's cool you didn't have to change the entire board like some people recommend. It looks like Marshall got a hold of some bad capacitors. The 2000 series amps sound really good when they're working properly. I have two Marshall TSL60s . Once I accidentally hooked my 4x12 into the TSL's effects loop and blew a fuse when I powered it up. After that I put yellow electrical tape over the effects loop inputs to make sure I'd never do that again. Good video!
I had a TSL JCM 2000 and it had this issue. Had to get a replacement board from Marshall. It has had about 16 reissues and was a big problem that Marshall had a hard time even figuring out. After the one board was swapped out it was fine. But holy shit what a nightmare. I eventually sold it
My mate had a TSL JCM 2000 that used to spend more time being repaired than played. Even when it was "working" it had a charming habit of having the volume slowly reduce as you were playing until you had the damned thing cranked 10/10 and could barely hear it over the drummer. It was like that from day 1 and as far as I know is still sitting in his music room semi-broken while he works overseas to make a crust.
Steve Kellett that sucks. It’s a shame they have a bad reputation because after I replaced the board it worked and sounded amazing. Just an initial bad design. Should have spent a little more time in R&D haha. I believe that was Marshall’s response to the dual rectifier. So it got rushed out.
@@omikl for the cost of about 10 bucks worth of parts this can be repaired. Korg USA will try to sell him a new board. He can fix the existing one. let me know if u want the instructions and I can send. These amps sound fantastic when working correctly
@@scottmacdonald5605 I'm having almost exact issues with my TSL 100 just after re-tubing (1st time &b/c power tube bad). 1st issues in 13 years, it's an '04, & for my tastes, I've always loved this thing's sound. ALL help will be GREATLY appreciated!
@@telorum1970 here is a link to the repair I referred to. Bear in mind that you need some soldering skills and fundamental understanding of assembly so that you ensure the amp is put back together properly. So long as you pay attention to where the various wires and cables that connect to the PCB go you should be fine. The important part of this repair is the isolation of the negative bias in on pin 5 from the adjacent high voltage in on pin 4. This is done by removing the power tube sockets and drilling out the via on the pcb at pin 5 on all 4 power tubes. Then you simply lift the end of the bias resistors of each socket and attach them directly to the now floating pin 5 on the tube socket. VIOLA! all fixed. Be sure to remove and inspect the small pcb that holds the bias adjust pots on the back of the amp. These can have broken solder joints due to misalignment of the pots so when the board is screwed in they come in contact with the chassis and can break the solder joints. Just make sure the pots are down all the way on the surface of the pcb to allow for proper clearance. Here is the link: www.hullerum.de/Marshall/TSL122repair.html Good luck! If you have any ? be sure to ask - Scott
Yeah the later Marshals are all most as difficult as the Mesa Boogie's to work on. They just keep adding crap. But Boogies add more in a smaller space. 100 lbs of shit in a 10 lb bag.
On these amps I always have to replace the caps in the bias circuit and if I cannot dial up to 90mv per side then change out the bias range resistor. Tube matching range also is a problem so your mA readings vary with what pair of tubes your running. Mark
I had the same problem with my 50watt head. Unfortunately my tech said it was all too hard, the mother board was stuffed and I had to say goodbye to it. So sad , it had been my favourite for a few years! Wish you were my tech...cheers from Downunder......
HI Twobar! Be worried! Get this! - drtube.com/en/modifications/jcm2000-stable-bias-mod my humble opinion is that this will fix it & stop it ever happening again.
Had a bias runaway with a 2000 series last year and after a good deal of research on the internet, the only way I solved the problem was to remove all 4 PA valve bases and dril 6mm hole where each grid pin came through the PCB, refitted the valve bases and wired the grid stoppers directly to the grid pin. What's happening is the PCB coating is conductive (Marshall know this!). this stopped the bias runner way. ALSO some of the random noise from the speaker was due to the track thickness on the heater circuit not suffient to carry the large heater current. I therefore rewire the heater to all valves with good quality heavy cable which cured the noise problem. My advice to engineers who get these amps in for repair is - run for the hills!
Hi Geoff wow interesting info thanks for sharing mate! So it was the COATING on the boards that was conductive ay? Do you mean like the conformal coating lacquer, or is it the solder mask or the screen printed layers? Curious that it was only around the screen terminals & not around the anodes. Geez Marshall must have had halfwits working for them when the 2000 series came out - so many problems. They may go out the way Gibson did! I can see the Fender guys rubbing their hands together in anticipation!
Lots of Marshalls are like this. Either replace it with the final 'issue' board, or you'll keep having problems, in many cases. The new issues are simply because they messed up...they didn't issue a new board because the old ones worked.
@@gazjscott Hi Gaz! Revision 20? Really? It took them 20 goes to get it right that's bloody ridiculous if you're correct! It's actually shameful really. These people have being building amps for 50 years now so you'd think they'd know better. Get your shit together Marshall!
I'm sure it's REAL helpful one year out but it may actually be one of those JJ tubes, I have a Fender amp that had 6 6l6s in it and one actually internally shorted and blew every (going on memory of what my tech told me) resistor(the 470 one) on the bias on that side, took out the B+ line, melted the wire on the heater string, and literally melted the tube socket from how bad the arc was. He literally had to rewire the output side of the amp. If it had been a PCB it would have basically been trash. This is not the first time I'd had an issue with JJ output tubes, I had one redplate new out of the box with bias that was absolutely perfect in a Pignose. Both of these amps were working just fine when they failed, with different tubes(biased according to JJs), and I'm extremely lucky it didn't completely kill the transformers on the Fender. Wish I had a video of when it happened, damn tube must have lit up like a light bulb.
The first repair I ever made on an amp was my JCM 2000 401 that would intermittently loose power to the tube heaters. I was nervous messing with it but luckily it was a common problem with the bridge rectifier. I later sold that thing and people like you have inspired me to use more vintage style amplifiers and I couldn't be happier with the tone and serviceability.
the internal layout of that DSL makes me want to barf. How many more features over a JCM800 does the DSL provide to necessitate that schematic atrocity?
I love R8's & R'9's myself but I only own a Standard, oops wrong video. Just kidding, thanks for sharing your knowledge Brad great video as always. I have a 1988 fender "the twin" and it needs some work on it bad. Crackles and pops all day. Probably needs all new caps and tubes.
One thing you didn't mention though you kind of demonstrated it when you were adjusting the bias. The bias on these amps is push/pull meaning you have to adjust each side to the point where both are as close to even as possible but to do that, you have to go back and forth as raising one, lowers the other, etc.
@@AnodyneHipsterInfluencer When I started to learn how to do point to point in building my own audio tube amps and pre amps,I can't be bothered to do anything with a pcb,not even a basic power supply,i have seen people do point to point with IC components ,resistors and capacitors,beautiful layed out wiring,and is truly a work of art.
My TSL 100 seems to only blow the 1 amp fuze on bigger stages with lighting etc. i plugged it in and it blows before even turning on standby. All the lights on amp are on but no sound? Will a good surge suppressor help?
I have a JCM2000 DSL 100w from 1997. Mine was one of the first ones off the production line because it was an artist endorsed amp. The amp ran about an hour before the tubes started melting down. The problem (amongst many) was the bias drift. All the boards were changed and several components were upgraded. What a major pain in the ass. But in terms of sound, it s the best Marshall I've ever had. It's been in service for well over 20 years and since the boards were changed out, I've never had a problem with it.
Exact same thing happened in my TSL, same resistor exploded and took out the smaller 1/4 watt below it. I had just installed a quartet of JJ 6CA7 tubes and "it go boom" too. Replaced the 1 ohm resistors with flame proofs. My board is the darker green version although not the latest issue. The amp is from 2006. I put the original stock Svetlanas' back in and no fireworks. I'm going to check the cap you replaced on mine. Another poster said these Marshalls' don't like JJ tubes. Looks like there's a trend.
I'm still burning in and testing for now, but still not blowing with a proper speaker cable and cab. If it does it again, I'm going to advise some new power tubes. This customer had already changed these before bringing it to me.
Last night, couldn't sleep, couldn't play guitar because it was too late and the British police are on your case if you're being too loud but won't do a thing if you complain about noisey neighbours yourself... I guess they don't like Psychedelic Stoner Doom being played through a 6x12 rig... So, solution: I had a Guitologist marathon with plenty of home made ice cream. I particularly enjoyed the Train Club one. Great stuff! :D
I have a 1998 model and a 2005 model of this dsl100 amp.Back in around 2000,I bought the 1998 from the now defunct mars music.I had it for a couple of weeks,and it started blowing the HT fuse.So I replaced all the tubes.It didnt fix the problem.I then took it to a marshall service center which was less than a mile from where I lived.They kept it for about 3 months,and finally called me to come pick it up.That they couldnt figure out what was wrong with it.They only charged me about $40 to work on it.Even though it was still under warranty.I asked them what they thought the problem might be?He said he thought maybe it was the power transformer.So I decided to try and troubleshoot it myself.I have an electronics background,and have worked on tube circuits before back in the 70's.I must have spent over a hundred hours or more working on it.And I never got anywhere.My problem was the drifting bias.It would steadly climb on its own.I resoldered everything on the mainboard.Even replaced a bunch of caps,and resistors.Nothing would fix it.Finally I read somewhere on the internet that it was the mainboards circuitboard that was defective.The material in the mainboard that would conduct and act as a conductor.So I decided to retire it away in the closet.A new circuitboard wasnt available at the time.The only way to get a replacement board was to ship it to England,or take it to England,and they would replace the board while you waited.But they would ship you a new board.So I decided to buy another brand amp.It didnt sound as good,but at least I could play my guitar.Finally I got tired of the bad sound from the other brand amp,and decided to buy another dsl100.So I bought another one from Guitar center in 2005.Anyway to make a long story short.I kept checking to see if a new board would become available.It did.But I couldnt order it directly from the distrubutor.I had to order it from a retailer.Once I received the board,I changed it out,and the problem went away.I also read that the 2005 model was also suseptable to going bad.So I bought another new board as a spare.I also checked the bios for drifting.It does drift after a couple of hours of playing.But not enough to go way out of range.But I suspect eventually it will go bad.because the new boards bias is rock solid,and doesnt drift the least.I havent played much in a few years.But I want to replace that board before it actually goes.Since I still have the new board.But you know how difficult it is to unplug all those connectors,and mark everything.I definetly had taken photos before I removed it before,so I would know if they were on correctly.I also had marked everything with tape.
God forbid they name them like Con5a to Con5b. Have that same Fluke DMM, love it! Cheap tools are great for a lot of stuff, but the DMM is not worth skimping.
So normal operation of the 1ohm cathode resistor is 0.0081W. So this will never go if there is not a very large overcurrent. And you never need to replace them with larger wattage ratings. First you always measure the bias voltage on the tube socket when that happens. The failed cap feeds the bias voltage circuit and when the bias voltage fails....kabooom.
Your chuckle after going through all the connectors and wires to remove the bottom board was hilarious lol. I do not have a marshall amp like that and had no need to watch it lol I picked up a 1961 Electrohome made in Canada 3W four tube Portable Record Player that looks like a suitcase on kijiji for 20 bucks. Plus the guy delivered it lol. It just humms like a mother effer. Level knob does nothing. Balance knob does nothing. Bass and Treble Both seem to do something. No noise without tubes in it. Just wondering if that could be a output transformer issue? I don't have a tube tester but ordering tubes now. All the electronics look pristine. When you open up the case it smells like an old mans cabin. Love from Canada :)
Justin B. The first thing that I'd suspect would be the B+ filter capacitor-they tend to dry out. When this happens, the capacitor value goes WAY down, thus the hum
An amp of that age, change every single capacitor in it. And since it started life as a record player, you'll want to modify the circuit to optimize for guitar use, if that's what you're using it for.
Hey!!! Thanks for taking your time to answer!! I have just picked up caps and am about to plug in the soldering iron. I'm going to just restore it as is and go from there. It's in immaculate condition and I have some vinyls. If it craps I'll guitar amp it lol. I am working on videos as well so I can share my work with you fine folks. Love from Canada :)
I do need a better one if I'm going to do more of these modern amps. Sometimes my old one doesn't tell me everything I'd like to know. I'll get one someday.
Answer: DIY a µTracer...cheap (about two (!!) hundred bucks:) and you can test tubes even savely beyond SOA and even under conditions unable to see in real world amps, never ever (also the usual tests are easily to be done as well)...also you can match tubes in a way nobody else can do without a MuTracer (you can put plots on plots on whatever condition you want in order to match tubes by)...but you would need a PC for control and graph readouts. But you also gain a dynamic transconductance measuring device and also you can do all 2nd order derivations (like distortion analysis for a tube due to unlinear behavior) and some 3rd order integral calc stuff (like reflected pseudo-impedances caused by the intrinsic inter-electrode capacitances)
Love how all the technology recommended is far beyond what was necessary 65 years ago. I got my equipment from the Supervisor of the Schenectady and Syracuse NY plants. He only used a Heathkit 600a tester and a Tektronix T921 Oscilloscope. This guy built the biggest amplifiers I've ever seen. 200lb monsters for Ham radio use. Anyone who knows who I'm talking about his handle was W7EEE, and quite frankly the most admirable figure I've ever met. He has passed away but truly a pioneer.
These boards are notorious for bias drift issues. Board builds various creeping paths such as between B+ and Bias feed voltage - on the right most Screen Resistor. Also on the sockets themselfs and the PI circuit. Im actually rather surprised here that one of the 1 ohm resistors was shot. In order to shoot out a 1 Ohm 2 Watts resistor you need relatively high amperage / engergy which is unlikely to flow in a tube between Anode to cathode as they have a very high series Resistance, even when turned full on. At the same time, even if the heater to cathode would short - where enough energy is available, its still only virtually grounded via 2 100 Ohm Resistors. So there again is not a huge energy to be expected. Anyway... what i find strange is that i had worked on a couple of DSL / TSL (reworking boards, swapping boards and so on) and in 70 percent of cases i would say i had ark over in one tube aswell. What i find interesting is that its always the same socket 3 so as you had in your amp. Nice video. Thanks for that
My JCM 2000 DSL 100 is missing a few dial indicators so I have no idea what my settings are, two middle power amp tubes weren’t working so I pulled em’ out, green channel stays clean no matter how high the gain. My MG cabinet is too narrow for the amp head, so my half stack looks like a cross. It sounds freaking killer!!! I’m afraid to have it serviced. It might kill whatever mojo it has. Someone gave the amp to a guy in exchange for some Cocaine. He never came back to get it so it got passed around town and ended up with me, It’s ghetto fabulous!!
The 2000 heads mistakenly installed 220k ohm grid stoppers where there should be 5.6 k ohm grid stoppers. This causes bias instability. I still say they are E-waste disguised as an amplifier.Boards that conduct,d.c.rectifier heater failures, 4 and 8 ohm ground through the 16 ohm shorting jack that heats up and looses ground. Buy a 900 or an 800 if you want a Marshall and save yourself the headache.
Hi Brad! Great video! I'm 4 years late of course - sorry about that! I called the pt, but it looks like I was wrong! D'oh! You got stuck with a diabolically (sp?) nasty amp there mate, with multiple intermittent simultaneous faults - the worst kind of fault! Then you had incorrect components compared to the circuit to contend with. The less than obvious failure of C2 You did very well. I don't think it's necessarily quite finished with you yet. I think you've shut it up for a while, but unfortunately I think may see it again. Apparently both tubes in the pair have the same problem with the increased conductivity with increased temperature. Well I guess it's been 4 years, so has this amp been back for another service yet?
Thanks for the comment. I think the one bad cap could have been the problem. If it was damaged and arcing internally at full voltage, it could have been like throwing a switch, causing spikes. It was the only damaged part I found other than the 1 ohm cathode resistor. But it's possible the previous set of tubes caused the resistor to blow and my gator clips on my load blew the HT fuse both times. I burned in the amp for another hour or more last night and played the heck out of it...no issues. I plugged into the 412 cab with a proper cable this time. You could be right, but I'm not convinced.
I saw the Pawed Gretch give back and i cant find tat video ? Alougth , it broke my heart that guy iz a REAL DEAL MUSICIAN ! A real musician helpz other musicians ...If they can It reminds me of the. SG i lost that i bought the nite before i lost .my. Wife ...some of her last wordz to me were I luv tat guitar! And so i to all the plastic bell, pickgaurd, and rear electronic plates and those were chromed also...i kno dont hav. Any thing to do wit tiz vid, but I wanted to tell ya my story I am a poor man by all mean z ...but maybe Some day i will get another 2015 cherry sg or other year and memorialize it for her.. I luv ya repair vidz they ARE my fav videoZ ON here im not bad tech but watching you teachs me tingz i didnt kno as good az i do now im 1 of ya biggest fan z .....But the Guy ya showed reuniting him wit his Gretch guitar brought a tear. ....To my eye.. Thx for all ya taught me regards Shaun
have a 30 yr old Peavey VTM60.Tube amp. It's the Peavey that marshall wanted the 800 to sound like. LOL Never had a problem with it. I don't see any on the web having such trouble like the marshall's and Boogies and... UA-cam is full of "top of the line" tube amps being repaired. I like tube amps but I will never pay the price for the newer ones knowing how they're put together.
Run Bias Run. The board could be a blem board assembler at Marshall had on the shelf for a while. They were in a rush to move all these amps out of the factory for their newer counterparts called DSL which is the same as JCM 2000 I've read the second generation DSL100 from 2017 early ones that replaced jcm 2000 last years 2000ish suffered same issues. But the newer 2018 DSL 100's are way better Marshall fixed all the issues from customers complaints & added a few new features. Does the JVM series have same issue, Bias runaway?
Oscilationis the problem.You must place 1k resistor close to tube socket on input of each tube just in line with input and 470k between same resistor and earth, and tube should quiet down and bias should be set to 33ma each tube for aprox 450volt. If above 500volt then max 30ma..
I think Marshall needs more wires in their amps. Nothing is more impressive than a rats nest of colorful wires. I'm working on a Fender Cyber Twin that likes to blow the PS fuse for the digital circuit. Doesn't look like it's going to be nearly as fun as this Marshall, though. ;) Cheers!
I have been watching you for a few years now and you've not only inspired me, I get allot from you're electronics knowledge and guitar playing, I play and I do work on electronics as well. Back in the 80s i worked on VCRs and stereos etc, I played music as well.(in church). During those years electronics was only a side job and I had to stick with working with my dad in house exteriors...... not quite my interest but I had to make a living..I started a small recording studio and I did pretty well with that but that was before things went digital and folks could buy software for their computers lol... Long story short I recently got back into playing and singing and working on radios and amplifiers... pretty much had to repurchase equipment over the past few years, lol Thanks so much for your videos Brad. keep em coming when you can..... prayers and blessings, love and peace, safety and prosperity for you my friend God bless!!
When the fuse blew it sounded like you dropped something nearby, causing something in the tube to rattle and short out causing it to spark. I'd be suspect of that tube, give it a few taps to test.
Your patience is beyond mine.. I owned a Marshall once. Hahahahaha.. About now.. Iwould be in the bottom of the hudson river at this point... 36 MInutes in It be parts. Or sunken.. Hate modern shit even though I own some. But I won some old shit too. Used to own very old stuff I wish I never sold now. They have turned to gold.
Screw the DSL. Mine fried a tube that took out some resistors and a tube socket with it. But I did enjoy your troubleshooting. Mine was screwed up as bad as this one. I love working on my hand built plexi clone compared to the DSL or HVM.
I had another one of these to check over couple of weeks ago and one of the screen resistors had fell completely out and was rattling around in the box !! Hahaha great soldering they did....
I had this same head, worked fine until it didn't...left it at a repair shop for two months, they couldn't find the problem...another shop quickly found it was a faulty fuse holder :(
Another idea. Why did the tube spark? Could there have been a nasty quick burst of parasitic rf happening? I have been known to add screen resistors in amps where they were absent and increase their value slightly in amps already with them. Also any screen or grid-block resistors must be as close to the tubes as possible - preferably right on the socket. And I never use anything less than a 1-watt power rating cuz the little guys are too fragile. Besides we are dealing with high voltage, and bigger resistors resist high voltage spikes better than small ones. In my lab where I operated and maintained a 2.5 mega volt van de Graff we were always concerned with resistor spike voltage ratings too, besides their wattage.
Brad the beauty of your channel is that I watch EVERY video for no real reason
Thanks for watching!
Working on this same amp (combo) and thanks so much for explaining the tube swap voltage test. Just tested it and the values carried over when I swapped the tubes. Screen recorded this to have it in my back pocket. You’re the best Brad!!!!!
Man I just can't get over how valuable these videos are. I have an MTS Carvin... Well gave it to my old girlfriend and thus don't have any tube amps anymore but these videos are my type of TV. Always learn something. Every time.
Kickass. Glad you dig 'em.
My kind of TV too. This, and dick Cavett lol.
I bought a JCM 2000 used and after a week or so it developed a similar problem. Sent it in for repair and it came back sounding great. That was 5 years ago and it's still going strong with no problems. Love that amp.
I got lucky with my TSL 60 heads I owned for about ten years, about 6months after i sold them they started to have problems and this was one of them.
I would have never guessed to be looking at Capacitor C2 since it was bad on the high tension circuit.
I've bought one from a customer for £50 , as the solution to the runaway bias from the conductive pcb is a new board from Marshall , £125 , I think was the price . Plus labour , not cost effective for him .
But eventually I'll modify the old board with the "Dr Tube" drill and mod method . I think I paid £60 for the kit .
This is so weird- my jcm2000 DSL100 is following the same exact issues in the same order as this one. You're saving me a yit load of troubleshooting time. Thanks!
The tube is bad, exhibiting a "flashover" due to gas inside. This essentially shorts B+ to cathode, popping the resistor. Change the tube.
Brad, I was trained by the Navy as an avionics tech, back in 1970, and used to enjoy tinkering with tube amps (as a bass player since 1967). This video, however, has convinced me beyond all doubt that I never want to see the insides of one of these newer monsters!! God bless your patience, persistence, and curiosity! LOL You're a better man than I, McGee! LOL
Is your piece of trash a fuse?
Thanks Norm. Can't say on the trash til tomorrow.
I owe you some dough because I had to put in a new JCM2-60-00 Revision 20 board in and you helped me with that. Thanks to you, I also bias'd it. It was WAY off. If you have a paypal or another method, I'll send you $50 because you saved me at least $200 so far. Thanks and I hope you all are staying safe. Great videos.
Man i had a TSL 100 that would run away. Id send it to my guy hed bias it then give it back and it would do it again. After about 3 sets of tubes i did some checking and found bias resistors that woukd thermal reactive. They would change value with a hair dryer on them. Finally got a new main board and the problem went away. Funny thing all thise suspucious resistors were changed to better ones. I hate engineer bean counters. Now i play a metro and a matchless. No more pcb for me. Keep on keepin on.
Question: how do I send my DSL to you because honestly I have no interest in knowing the secret voodoo that you know that fixes these! I am hoping you still do repairs!
Hahaha bro! Yes, my amp guy just keeps saying, “just bring it back it’s no biggie”. A week later it goes out and he says, “just bring it back no biggie”. 🤣
At the 24:00 mark and I now know why I'll never buy a Marshall not made before all this integrated bullsh*t.
Kudos to you sir. You know your stuff! I blew my amp the other night. Same one you have here (JCM2000 DSL 100 watt into a 1960 dsl900 4x12 cab). I was playing on "2" for about an hour when my other guitarist decided to crank it at practice. I got tired of him blowing us all out, so I turned the amp up on 10. Struck one chord and... crickets. Used my backup fender amp to finish practice. Now looking further into my prob, I see that an EL34 has blown. Looking from the back of the amp, it is the left outermost tube. I also blew the D198 250 VA fuse. No smell in the amp so I hope I didn't blow anything else. Didn't make note when I unplugged everything (it was late) but I believe I mistakenly had the cab plugged into the 8 ohm output on the amp. :( It played for an hour, so, I'm not sure if the ohm mismatch blew it or not. But if it did, where else would I have issues? Also, where can I get another D198 fuse? Thanks so much for any help you can give!
If you ever found the answers to your questions, PLEASE LMK! I am fairly certain that my ORIGINAL prob (way back) was accidentally playing through mismatched cans. Now I just re-tubed, & blew HT fuse. I've got a lot of digging & video watching & I'm dying to get back into playing now! (Plus been working 6-7 nights/ week lately... I know, I'm pitiful... all help much appreciated!
Thanks for this video Brad, this was really interesting. Blew my mind when that particular cap measured so bad. Lots of plugs and wires to disconnect and mislabeled schematics from the factory, that’s kind of an automatic handicap right? This was cool 😎 as usual, you rock.
Connectors are never as reliable as solder.
Why do you suppose they would have put so freaking many connectors and plugs in? Just because it was easier to pay someone to build the parts piecemeal and then pay someone to finally wire it up? I bet that was it, to save a tiny bit of the almighty dollar. Oh, I forgot, save to pound. Pound sand I say...
@@TheGuitologist I just found & subscribed to your site about a week ago. I picked this video (hoping for a bit more advice & I'm on a time frame) but I've got an '04 TSL 100 & just getting back into playing after a few years off (& DYING to hear that Marshall & 1 of my Explorers) so I re-tubed last night before work. I had been playing it last week when I noticed the 1st power tube was just shot, dead. Anyway, it made a little sound before I killed the Output Mute & then V.P.R. buttons, then blew HT fuse. All tubes were still lit. I do factory automation/ maint & WILL soak up much from your experiences. I appreciate you doing what you do & helping others. I guess 1st question... I was sold 4-ECC83 S's for the pre-amp. HOWEVER, the original Marshall tube was still in the far left position w/the can/shield on it w/the nomenclature VLVE00064
WK43 on it. Do I need to go BACK to the music store and get a different tube or will the ECC83 S be ok there??? Looks like I'll be watching videos all day and possibly weekend and pray hard & often! Terrible timing w/just getting my FIRE RELIT.
1 last thing. I brought home a 5pk of Buss GMC-1-R fuses for T-shooting my issues. I'm guessing from what I've been learning, that's not a good idea...? Do I really have to go find some F1A L250V fuses for my t-shooting? Thanks for ANY help & I WILL be buying some swag asap!
Bad layout, what a waste of a PCB I see this too often with modern amps they design them to be throw away BTW that wire you mention isn't dark purple but Deep Purple
Mate ! , I was waiting for you to find an intermittent short on/in, a power tube .. I shelled out for a tube tester to eliminate faulty tube dramas at 1st base.. I read up on tube control Bias a lot lately , and i find the current sensing resistor , is there not only to reference milliamps to millivolts , but it is also to protect the control grid like a fuse would .. which is why you only should use just a half watt , 1 ohm type . (of course if you use 10 ohm , it would show 10 mV for 1 mA).
When i build a fixed bias amp, i make sure i have available, as a bias voltage , at least 10 % of the plate voltage , at the middle of the bias pot travel . so if the amp idling( all volumes and eq turned down to 0), has a plate voltage of say 480 dc volt ,, i want -48 v on the centre of the bias pots travel .and i want to be able to adjust that by 25% each way at least .
There could be a problem in your bias voltage supply .. crap filter cap , resistor ,, and make sure you have a decent negative voltage on the control grid . Pin 5 on that octal tube..
Over here in Australia , the amp companies built large amps with insufficient bias control , and the same with heater current . i had an amp built here that had 6 of EL 34 and 3 of 12 ax7's , and the heater winding for the power tubes was only good for 6 amps, which is why it chewed through tubes , stripped the damn cathodes ! when the fault takes out the current sensing resistor , its preety much saving the output transformer from dying ! Cheers Brad ,, love your work ..
I'm sure I'm late, but it's one of the little parts from a 3p3t switch from an effects pedal.
Love the channel Brad, I'm a first year Electrical Engineering student in Canada, and you really inspire me. How would you go about learning more about tubes and amplifier circuits? We dont cover Tubes or anything like that in any of my classes and this is the industry I want to work in. Thanks again,
Anthony
First, buy and read these books: amzn.to/2FFGyWa
amzn.to/2FKXMBq
amzn.to/2FGnGX8
Watch ALL of Uncle Doug's videos. Then come back and watch all of my videos. Then watch all of D-Lab's videos. Drop out of school. Piss parents off. Be happy. :D
May i add: DeepBlueHarp, ElPasoTubeAmps, Joernone and, of course, Dennis Carter and Mr. Carlson´s Lab and be and stay curious, do DIY from scratch and if anyone say "not possible" Do it...it´s a ton ´o´fun...(DrehKoPhaser, AllTubeSynth)
And repeat these three by heart (and for sure at 02:17AM when interrupted from sleep): R=V/I, P=V*I and f=1/T=1/(2*pi*C*R) there´s nothing more to know...you can go through pretty much anything tube related using just these three, of course, you would need to know them inside out and: by heart and it must be a pleasure for you to juggling around with them letters, by head not on paper;)
Buy: The Art Of Electronics, all RCA tube manuals (at least see them once 1:1 in a library if you downloaded them as PDFs)
And learn to solder with both hands in equality...;)
Good suggestions TubiCal.
This reminds me of Robocop (1987) The footage of the creation were it cuts in and out with cussing and partying.
That's my wife's favorite movie.
I will announce the winner of the "identify this trash on my sidewalk" contest tomorrow.
Internal push switch contact! Not a rocker contact!
That's the rocker out of a 3PDT foot switch.... as used in many stomp boxes.
its from the Bypass pedal switch that you got in trouble for. LOL
Creation Labs MK 4.23 Boost Pedal missing third piece of the foot switch
It's a red brick walkway with mortar grout .
Sorry Brad, I think you missed this one and this amp will be coming back. A power supply cap can't burn out the cathode resistor or cause that tube flash. Assuming that tube still works, I think that tube is shorting. That's about the only thing I can think of that would cause that flash. If the tube is now dead, then there was excess current though the tube and it burned out a wire inside. But if loss of bias can't do that, then it suggests a internal short. It happens. That why tube checkers have tests for shorts.
That cap is in the HT line. It was the only bad component on the entire HT I found that was bad. Granted, I didn't go all the way into the preamp, but I did check all the solder joints in the preamp. I think it was that cap. It would be a very unique problem if a power tube was shorting one second and fine the next.
I could see the cap blowing the fuse, but not the tube flash. Yes, an intermittent tube would be unusual, but not impossible. Intermittents are always a %&#$. If you correspond with the other guys like Uncle Doug or D-Lab, you might want to run this by them.
If there was a high voltage spike because that cap was misbehaving though, it could cause a tube spark. At least it makes sense that it could in my mind. As for Uncle Doug, I don't think he ventures much into modern amps. Terry at D-Lab may, but I don't know what he could tell me that I haven't already tried. I've read a lot of forum posts where techs are advising some to up the value of that HT fuse slightly to avoid problematic fuses, and I do agree that like a 1.5A fuse probably wouldn't hurt a thing, and may prevent some fuse blowing due to transients. But I think the issue with this one was that cap at first, which took out the R9. Then my shoddy speaker connection likely caused the later fuse blow. I played the amp for a long time after that and no issues. But yeah, intermittents are a pain in the ASS.
Time will tell. All I can say is my "tech sense" is still tingling. It won't give me a "warm fuzzy". But I understand the situation. If you can't recreate it, at some point you have to send it back to the customer. The only thing I can suggest is to make sure you test it with it sitting on the speaker cabinet so gets vibrated.
I totally hear you. I didn't get "that warm fuzzy feeling" either on this one. More like I had to jump out of bed and out the window putting my boots on. FWIW, I spent a good while I didn't put in the final video chopsticking with the amp on, and I played it and burned in a good long time. Like you said, the ghost won't show itself, maybe it went away?
Thank you for posting this!! Could this the be cause of my sick DSL? I can't wait to find out! Geez, much cheaper than replacing the socket PCB... that I already spent money on :( Marshall doesn't include those plastic stand-offs with the new board and repurposing the orginals barely works :( Not even sure where I can get new ones. I need some!
Try Mouser for the plastic stand offs.
Love these videos, I don't even own a marshall I just like seeing things being traced and fixed, we're all nerds I guess, keep up the good videos! Now everybody with a 2005 with same symptoms can learn what's going on with it, :D
I had one of these. Same problem and it ended up burning the board. Something to do with the PCB design and traces of the earlier ones. Amp tech bypassed those traces by hand wiring that part of the circuit. He called it 'lifting'.
PLEASE HELP ME SIR! I have a BIG PROBLEM WITH MY AMPLIFIER! I TRIED 1 WEEK TO SOLVE THE PROBLEM SO I NEED YOUR HELPP 🥺🥺🥺
I have a Turkish Marshall 1987 x amplifier clone from 70s. No matter how I try to fix, the inner power tube red plates whenever I play my guitar. Even though I changed the tube’s locations, the problem still continues. So I came up with that tubes do not have a problem but socket does. I even change the phase inventor coupling capacitors. I measure the colts in the grids of power tubes and it was -40 volt which was a suitable number. One of the screen resistors of the other non problematic tube was blown and I have changed it in case there was an imbalance but nothing changed.
Check for bias on the grid of the power tube that red plates, there should be somewhere around negative 26 Volts, on that grid, and the same as all the other grids. You can take the tube out (take all tubes out) and measure the negative volts on the the grids (at the pin for grid itself), they should all be the same and close to 26 volts for the 1987 Marshall with EL34's. If it is lower, then repair the bias supply, which is , a diode, filter cap, and a few resistors, could also be You have to retension that tube socket sleeve, because it is not making good contact with the tubes grid pin.
@@Geopholus you are the best! thank you so much
@@hazal3225 Let me know how it goes,..Elevenous Amps facebook
Excellent!
How many times did you say mother F er when you were working on it?
This should have been called the nightmare of all Marshall amp repair videos.
You have much more patience than I do. :-)
I can only repeat such language in my Gibson videos.
Hahaha.
Gibson makes me utter dirty words too.
just replace the board with a rev. 20 cures everything !!!!!!!!!!!!!!!!!` I isolated tube pin on all power tubes and jump a wire V8 5 pin too R10 resistor ,, v7 5 pin to R resistor . V6 too resistor and v5 too R7 resistor that cures bias runaway as temporary solution till I received the new Revision board but the Green board itself is very unstable too extreme heat ,, the Version 20 board solved all the issues $200 for new board well worth it these are by far the best sounding Marshalls I have the TSL 100 version .. The amp your are working on the version 7 board could have caused all the other issues also
Gr8 info! Options are starting to open before me. Personally, I love the sound of my TSL 100 & 1 of my Explorers...
JJ tubes are GARBAGE!! just had the same problem. Replaced tubes.. Also, 1 ohm resisters...and the bias feed R77 I think..should be 3.9K..on that one, it might be 10K.. put a 3.9k in there..make sure the 220k gets back down to 5.6k.. and I PROMISE IT WILL BIAS... also Marshall is full of shit.. DO NOT BIAS THAT TO 90! bias it up to 78 and itll be great!
in case you didn´t know: JJ is the only (!!) large number tube producer left in the western world. They do tubes for nearly all vendors, regardless what´s stamped on. All tubes around here are made by JJ, or they´re made in russia (=C=, svetlana(origin), electro harmonics (brand),RCA (brand), TungSol(brand), simply check tubes.ru for other brands you used to know.
I visited the saratov plant years ago, before they went by the "NewSensor" name they done tubes and they still do tubes) and china (they even use TESLA nowadays,RCA,amperex,WE and other formally well known tube brands)
I have a 2002 Marshall JCM 2000 DSL 100. It had the bias drift problem. A few minutes with a Dremel and four new grid resistors for the power tubes and the problem is solved. Bias is rock solid. Touched up the solder joints on the bias adjust board while I was in there since that's a common failure mode (cracked solder joints). The amp plays great now and runs very stable. These amps get a deservedly bad rap for poor engineering of the main board but it's an easy fix and you end up with a great amp that rocks.
90mv is 45ma per tube - hot! Those pots are highly interactive. I was thinking that they adjust the tubes on the opposite side. C46 has a tendency to blow short. You are lucky that you didn't have the dreaded conductive PCB issue, which requires some work with a Dremel. Thanks for the tip on those caps.
Yeah, you gotta jump back and forth to get the bias set.
I thought when he said 90 in the video it was awfully damn high. Those resistors likely fried whenever you cranked the hell out of it trying to get it set to 90. 30 is on the cool side and 45 would be hot as a firecracker with a set of your favorite humbuckers. The bias on mine was just set between 33 and 35 if I'm not mistaken.
Brad, I have fixed the Thermal Runaway issue with these amps. The circuit board material becomes conductive over time and then the tubes loose bias and then runaway. I isolate pin 3 of all the power tubes from the board by cleaning around the pin with a dremel. Then a jumper wire is installed to complete the circuit that you have cut.
I was thinking at first I might have to do that.
I sat through it 4 no reason. Lol I own a Marshall class5 head on am egnater cab. But iv been binge watching Brad for the last 3 weeks now. Its guitar porn..lol keep up the great work there Brad
For those asking, here is the link to the exact component tester I used in the video: goo.gl/FzQi7Z
Yeah Brad it's a nifty looking little tester & I might build one for myself. But I wouldn't trust it for one second with leaky caps to be honest. Use your multimeter for that! Or better still, I was gonna look into the capacitor leakage tester that Paul at Mr. Carlsons Lab designed. Looks like a fantastic device & the most sensitive I've ever seen! It can measure leakage through insulated wires! His design is apparently on Patreon. I'm gonna make myself one, & you probly should too! Make a video of it if it's ok with Paul. I'd definitely watch it.
The winner of the "identify the trash on my sidewalk" contest is John Anti! Congrats, John! You correctly identified that little piece of metal as one of the switch contacts from a 3PDT switch. It was, in fact, the missing contact from this video: ua-cam.com/video/OCdYNq6fYTI/v-deo.html Email me at bradlinzy at gmail to claim your prize. If John doesn't email within 24 hours, I'll choose another winner from the correct answers.
Love your vids... to think my first amp for Bass was a Linear Concord HiFi Amp all Valve back in 1962...then Selmer Treble n Bass 50watt heads & Selmer Goliath/David Cabs 3x Heads with 3x18 Cabs - proper music gear.... now about my 100watt Seymour Duncan 'Convertible' Amp - got it back in 1988-9 hardly ever been turned on and only in Studio setting... Guitar & Bass eh! tricky decisions. Thanks for Posting truly amazing and love the guitar playing. Michael @OAK77uk Tweetland/FB
It's cool you didn't have to change the entire board like some people recommend. It looks like Marshall got a hold of some bad capacitors. The 2000 series amps sound really good when they're working properly. I have two Marshall TSL60s . Once I accidentally hooked my 4x12 into the TSL's effects loop and blew a fuse when I powered it up. After that I put yellow electrical tape over the effects loop inputs to make sure I'd never do that again. Good video!
I had a TSL JCM 2000 and it had this issue. Had to get a replacement board from Marshall. It has had about 16 reissues and was a big problem that Marshall had a hard time even figuring out. After the one board was swapped out it was fine. But holy shit what a nightmare. I eventually sold it
My mate had a TSL JCM 2000 that used to spend more time being repaired than played. Even when it was "working" it had a charming habit of having the volume slowly reduce as you were playing until you had the damned thing cranked 10/10 and could barely hear it over the drummer.
It was like that from day 1 and as far as I know is still sitting in his music room semi-broken while he works overseas to make a crust.
Steve Kellett that sucks. It’s a shame they have a bad reputation because after I replaced the board it worked and sounded amazing. Just an initial bad design. Should have spent a little more time in R&D haha. I believe that was Marshall’s response to the dual rectifier. So it got rushed out.
@@omikl for the cost of about 10 bucks worth of parts this can be repaired. Korg USA will try to sell him a new board. He can fix the existing one. let me know if u want the instructions and I can send. These amps sound fantastic when working correctly
@@scottmacdonald5605 I'm having almost exact issues with my TSL 100 just after re-tubing (1st time &b/c power tube bad). 1st issues in 13 years, it's an '04, & for my tastes, I've always loved this thing's sound. ALL help will be GREATLY appreciated!
@@telorum1970 here is a link to the repair I referred to. Bear in mind that you need some soldering skills and fundamental understanding of assembly so that you ensure the amp is put back together properly. So long as you pay attention to where the various wires and cables that connect to the PCB go you should be fine. The important part of this repair is the isolation of the negative bias in on pin 5 from the adjacent high voltage in on pin 4. This is done by removing the power tube sockets and drilling out the via on the pcb at pin 5 on all 4 power tubes. Then you simply lift the end of the bias resistors of each socket and attach them directly to the now floating pin 5 on the tube socket. VIOLA! all fixed. Be sure to remove and inspect the small pcb that holds the bias adjust pots on the back of the amp. These can have broken solder joints due to misalignment of the pots so when the board is screwed in they come in contact with the chassis and can break the solder joints. Just make sure the pots are down all the way on the surface of the pcb to allow for proper clearance. Here is the link: www.hullerum.de/Marshall/TSL122repair.html Good luck! If you have any ? be sure to ask - Scott
Yeah the later Marshals are all most as difficult as the Mesa Boogie's to work on. They just keep adding crap. But Boogies add more in a smaller space. 100 lbs of shit in a 10 lb bag.
Boogies are marvels of EE, and they do make models that appeal to a variety of players, but troubleshooting them can be difficult.
dsl is to bright,, just unplayable amp. when will marshall do another late 70's jmp master vol amp"???
You need to play them through V30 speakers, because they are so bright, I agree!
You're a beast Brad! I won't touch these POS's, they're a liability.
Stuff like this is not for the weak-hearted. An intermittent issue in a modern amp can be a nightmard scenario.
It would help if Marshall made a good amp like they used to.. #Junk
On these amps I always have to replace the caps in the bias circuit and if I cannot dial up to 90mv per side then change out the bias range resistor. Tube matching range also is a problem so your mA readings vary with what pair of tubes your running. Mark
I had the same problem with my 50watt head. Unfortunately my tech said it was all too hard, the mother board
was stuffed and I had to say goodbye to it. So sad , it had been my favourite for a few years! Wish you were my
tech...cheers from Downunder......
I have a 2004 DSL100. Should I be worried? It also has JJ Tubes 😮
HI Twobar! Be worried! Get this! - drtube.com/en/modifications/jcm2000-stable-bias-mod
my humble opinion is that this will fix it & stop it ever happening again.
I caught that little bit o Slayer.....:)
I was trying to remember it. Been a long time. :)
EvilHomer1973 had
Had a bias runaway with a 2000 series last year and after a good deal of research on the internet, the only way I solved the problem was to remove all 4 PA valve bases and dril 6mm hole where each grid pin came through the PCB, refitted the valve bases and wired the grid stoppers directly to the grid pin. What's happening is the PCB coating is conductive (Marshall know this!). this stopped the bias runner way. ALSO some of the random noise from the speaker was due to the track thickness on the heater circuit not suffient to carry the large heater current. I therefore rewire the heater to all valves with good quality heavy cable which cured the noise problem. My advice to engineers who get these amps in for repair is - run for the hills!
Hi Geoff wow interesting info thanks for sharing mate! So it was the COATING on the boards that was conductive ay? Do you mean like the conformal coating lacquer, or is it the solder mask or the screen printed layers? Curious that it was only around the screen terminals & not around the anodes. Geez Marshall must have had halfwits working for them when the 2000 series came out - so many problems. They may go out the way Gibson did! I can see the Fender guys rubbing their hands together in anticipation!
Lots of Marshalls are like this. Either replace it with the final 'issue' board, or you'll keep having problems, in many cases. The new issues are simply because they messed up...they didn't issue a new board because the old ones worked.
I have a 1999 TSL 122 I'll try to see what board version it has tonight might already be replaced
Think the latest board is Rev 20 for these amps
@@gazjscott Hi Gaz! Revision 20? Really? It took them 20 goes to get it right that's bloody ridiculous if you're correct! It's actually shameful really. These people have being building amps for 50 years now so you'd think they'd know better. Get your shit together Marshall!
I'm sure it's REAL helpful one year out but it may actually be one of those JJ tubes, I have a Fender amp that had 6 6l6s in it and one actually internally shorted and blew every (going on memory of what my tech told me) resistor(the 470 one) on the bias on that side, took out the B+ line, melted the wire on the heater string, and literally melted the tube socket from how bad the arc was. He literally had to rewire the output side of the amp. If it had been a PCB it would have basically been trash. This is not the first time I'd had an issue with JJ output tubes, I had one redplate new out of the box with bias that was absolutely perfect in a Pignose. Both of these amps were working just fine when they failed, with different tubes(biased according to JJs), and I'm extremely lucky it didn't completely kill the transformers on the Fender.
Wish I had a video of when it happened, damn tube must have lit up like a light bulb.
Never have had a problem with mine ever
Colored zip ties, and matching paint = Seriously helpful when you have to pull unmarked harnesses that can be plugged in anywhere.
Wait until you get to do a Hughes and Kettner Triamp with all ther circuity and 13 tubes.
The first repair I ever made on an amp was my JCM 2000 401 that would intermittently loose power to the tube heaters. I was nervous messing with it but luckily it was a common problem with the bridge rectifier. I later sold that thing and people like you have inspired me to use more vintage style amplifiers and I couldn't be happier with the tone and serviceability.
Same.
the internal layout of that DSL makes me want to barf. How many more features over a JCM800 does the DSL provide to necessitate that schematic atrocity?
Not enough and the extra features aren't that good anyway.
I love R8's & R'9's myself but I only own a Standard, oops wrong video. Just kidding, thanks for sharing your knowledge Brad great video as always. I have a 1988 fender "the twin" and it needs some work on it bad. Crackles and pops all day. Probably needs all new caps and tubes.
Sounds like it's time for a spa day for the Fender.
One thing you didn't mention though you kind of demonstrated it when you were adjusting the bias. The bias on these amps is push/pull meaning you have to adjust each side to the point where both are as close to even as possible but to do that, you have to go back and forth as raising one, lowers the other, etc.
That is true. One side affects the other.
Hi Brad, one of the best variable tube amps from the big Jim M! Good job done!
Sidewalk item: rocker plate from a toggle switch ✌️
You beat me to it but that's my guess too.
Probably trash from the boost pedal repair ua-cam.com/video/OCdYNq6fYTI/v-deo.html
Sure looks like it to me. I think we won! Was there a prize?
YES!
Wow! this really makes you appreciate point to point :-)
Agreed. I'll never buy another PCB based amps. The closest I get is my 2104 JMP. Other than that, handwired, point to point.
@@AnodyneHipsterInfluencer When I started to learn how to do point to point in building my own audio tube amps and pre amps,I can't be bothered to do anything with a pcb,not even a basic power supply,i have seen people do point to point with IC components ,resistors and capacitors,beautiful layed out wiring,and is truly a work of art.
My TSL 100 seems to only blow the 1 amp fuze on bigger stages with lighting etc.
i plugged it in and it blows before even turning on standby.
All the lights on amp are on but no sound?
Will a good surge suppressor help?
90mv ----- 45ma a tube? pretty high for modern EL-34 tubes, got one on my bench, goin 60 a side c how it sounds,
I have a JCM2000 DSL 100w from 1997. Mine was one of the first ones off the production line because it was an artist endorsed amp. The amp ran about an hour before the tubes started melting down. The problem (amongst many) was the bias drift. All the boards were changed and several components were upgraded. What a major pain in the ass. But in terms of sound, it s the best Marshall I've ever had. It's been in service for well over 20 years and since the boards were changed out, I've never had a problem with it.
Lead free solder garbage ruins everything.
Can't have toddlers chewing on Marshall motherboards though! It's for our own good!
Man, thank you so much for these videos. I have learned an amazing amount from watching you.
Exact same thing happened in my TSL, same resistor exploded and took out the smaller 1/4 watt below it. I had just installed a quartet of JJ 6CA7 tubes and "it go boom" too. Replaced the 1 ohm resistors with flame proofs. My board is the darker green version although not the latest issue. The amp is from 2006. I put the original stock Svetlanas' back in and no fireworks. I'm going to check the cap you replaced on mine. Another poster said these Marshalls' don't like JJ tubes. Looks like there's a trend.
I'm still burning in and testing for now, but still not blowing with a proper speaker cable and cab. If it does it again, I'm going to advise some new power tubes. This customer had already changed these before bringing it to me.
replace with a VER 20 cures everything
Last night, couldn't sleep, couldn't play guitar because it was too late and the British police are on your case if you're being too loud but won't do a thing if you complain about noisey neighbours yourself... I guess they don't like Psychedelic Stoner Doom being played through a 6x12 rig... So, solution: I had a Guitologist marathon with plenty of home made ice cream. I particularly enjoyed the Train Club one. Great stuff! :D
I encourage this behavior, as does the local constabulary, I'm sure.
I have a 1998 model and a 2005 model of this dsl100 amp.Back in around 2000,I bought the 1998 from the now defunct mars music.I had it for a couple of weeks,and it started blowing the HT fuse.So I replaced all the tubes.It didnt fix the problem.I then took it to a marshall service center which was less than a mile from where I lived.They kept it for about 3 months,and finally called me to come pick it up.That they couldnt figure out what was wrong with it.They only charged me about $40 to work on it.Even though it was still under warranty.I asked them what they thought the problem might be?He said he thought maybe it was the power transformer.So I decided to try and troubleshoot it myself.I have an electronics background,and have worked on tube circuits before back in the 70's.I must have spent over a hundred hours or more working on it.And I never got anywhere.My problem was the drifting bias.It would steadly climb on its own.I resoldered everything on the mainboard.Even replaced a bunch of caps,and resistors.Nothing would fix it.Finally I read somewhere on the internet that it was the mainboards circuitboard that was defective.The material in the mainboard that would conduct and act as a conductor.So I decided to retire it away in the closet.A new circuitboard wasnt available at the time.The only way to get a replacement board was to ship it to England,or take it to England,and they would replace the board while you waited.But they would ship you a new board.So I decided to buy another brand amp.It didnt sound as good,but at least I could play my guitar.Finally I got tired of the bad sound from the other brand amp,and decided to buy another dsl100.So I bought another one from Guitar center in 2005.Anyway to make a long story short.I kept checking to see if a new board would become available.It did.But I couldnt order it directly from the distrubutor.I had to order it from a retailer.Once I received the board,I changed it out,and the problem went away.I also read that the 2005 model was also suseptable to going bad.So I bought another new board as a spare.I also checked the bios for drifting.It does drift after a couple of hours of playing.But not enough to go way out of range.But I suspect eventually it will go bad.because the new boards bias is rock solid,and doesnt drift the least.I havent played much in a few years.But I want to replace that board before it actually goes.Since I still have the new board.But you know how difficult it is to unplug all those connectors,and mark everything.I definetly had taken photos before I removed it before,so I would know if they were on correctly.I also had marked everything with tape.
God forbid they name them like Con5a to Con5b.
Have that same Fluke DMM, love it! Cheap tools are great for a lot of stuff, but the DMM is not worth skimping.
So normal operation of the 1ohm cathode resistor is 0.0081W. So this will never go if there is not a very large overcurrent. And you never need to replace them with larger wattage ratings. First you always measure the bias voltage on the tube socket when that happens. The failed cap feeds the bias voltage circuit and when the bias voltage fails....kabooom.
Lools like board hell on there. Same as my JCM900. Nice clean channel, lead is a dog. Need a "Z".
You say gator clip, we say clip lead. I wonder why that cap caused all this.
I like your style. You are very through and explain carefully everything you do. Great Videos and super channel. Hats off to you, man... Thanks
Your chuckle after going through all the connectors and wires to remove the bottom board was hilarious lol. I do not have a marshall amp like that and had no need to watch it lol
I picked up a 1961 Electrohome made in Canada 3W four tube Portable Record Player that looks like a suitcase on kijiji for 20 bucks. Plus the guy delivered it lol. It just humms like a mother effer. Level knob does nothing. Balance knob does nothing. Bass and Treble Both seem to do something. No noise without tubes in it. Just wondering if that could be a output transformer issue? I don't have a tube tester but ordering tubes now. All the electronics look pristine. When you open up the case it smells like an old mans cabin.
Love from Canada :)
Justin B. The first thing that I'd suspect would be the B+ filter capacitor-they tend to dry out.
When this happens, the capacitor value goes WAY down, thus the hum
Ok!!!! Thanks dude!~!! I plan on changing that as well just was trying to sort out output tranny before I get involved lol
An amp of that age, change every single capacitor in it. And since it started life as a record player, you'll want to modify the circuit to optimize for guitar use, if that's what you're using it for.
Hey!!! Thanks for taking your time to answer!! I have just picked up caps and am about to plug in the soldering iron.
I'm going to just restore it as is and go from there. It's in immaculate condition and I have some vinyls. If it craps I'll guitar amp it lol.
I am working on videos as well so I can share my work with you fine folks.
Love from Canada :)
What wrong with Marshall, doesn't look like great design an build quality...
Brad, I think you need a serious tube checker
I do need a better one if I'm going to do more of these modern amps. Sometimes my old one doesn't tell me everything I'd like to know. I'll get one someday.
Answer: DIY a µTracer...cheap (about two (!!) hundred bucks:) and you can test tubes even savely beyond SOA and even under conditions unable to see in real world amps, never ever (also the usual tests are easily to be done as well)...also you can match tubes in a way nobody else can do without a MuTracer (you can put plots on plots on whatever condition you want in order to match tubes by)...but you would need a PC for control and graph readouts. But you also gain a dynamic transconductance measuring device and also you can do all 2nd order derivations (like distortion analysis for a tube due to unlinear behavior) and some 3rd order integral calc stuff (like reflected pseudo-impedances caused by the intrinsic inter-electrode capacitances)
Love how all the technology recommended is far beyond what was necessary 65 years ago. I got my equipment from the Supervisor of the Schenectady and Syracuse NY plants. He only used a Heathkit 600a tester and a Tektronix T921 Oscilloscope. This guy built the biggest amplifiers I've ever seen. 200lb monsters for Ham radio use. Anyone who knows who I'm talking about his handle was W7EEE, and quite frankly the most admirable figure I've ever met. He has passed away but truly a pioneer.
Everything electrical runs on smoke. I’ve been in that business for a while. You let the smoke out... it quits working! 💨
The DSLs didn't suffer with that very often...
And also, DSL & TSLs HATE JJs.
These boards are notorious for bias drift issues. Board builds various creeping paths such as between B+ and Bias feed voltage - on the right most Screen Resistor. Also on the sockets themselfs and the PI circuit.
Im actually rather surprised here that one of the 1 ohm resistors was shot. In order to shoot out a 1 Ohm 2 Watts resistor you need relatively high amperage / engergy which is unlikely to flow in a tube between Anode to cathode as they have a very high series Resistance, even when turned full on.
At the same time, even if the heater to cathode would short - where enough energy is available, its still only virtually grounded via 2 100 Ohm Resistors. So there again is not a huge energy to be expected.
Anyway... what i find strange is that i had worked on a couple of DSL / TSL (reworking boards, swapping boards and so on) and in 70 percent of cases i would say i had ark over in one tube aswell. What i find interesting is that its always the same socket 3 so as you had in your amp.
Nice video. Thanks for that
On my gosh, you made it rain on strippers!!!!
A shock and vibration sensor that should have been in the package?
My DSL100 main board has a 220K resistor in R10, R70, R66, & R7 but 56K only marked in the updated schematic diagram, I’m having trouble firing up V7
My JCM 2000 DSL 100 is missing a few dial indicators so I have no idea what my settings are, two middle power amp tubes weren’t working so I pulled em’ out, green channel stays clean no matter how high the gain.
My MG cabinet is too narrow for the amp head, so my half stack looks like a cross.
It sounds freaking killer!!!
I’m afraid to have it serviced. It might kill whatever mojo it has.
Someone gave the amp to a guy in exchange for some Cocaine. He never came back to get it so it got passed around town and ended up with me, It’s ghetto fabulous!!
The 2000 heads mistakenly installed 220k ohm grid stoppers where there should be 5.6 k ohm grid stoppers. This causes bias instability. I still say they are E-waste disguised as an amplifier.Boards that conduct,d.c.rectifier heater failures, 4 and 8 ohm ground through the 16 ohm shorting jack that heats up and looses ground. Buy a 900 or an 800 if you want a Marshall and save yourself the headache.
Hi Brad! Great video! I'm 4 years late of course - sorry about that! I called the pt, but it looks like I was wrong! D'oh! You got stuck with a diabolically (sp?) nasty amp there mate, with multiple intermittent simultaneous faults - the worst kind of fault! Then you had incorrect components compared to the circuit to contend with. The less than obvious failure of C2 You did very well. I don't think it's necessarily quite finished with you yet. I think you've shut it up for a while, but unfortunately I think may see it again. Apparently both tubes in the pair have the same problem with the increased conductivity with increased temperature. Well I guess it's been 4 years, so has this amp been back for another service yet?
The capacitors on the AC board are snubbers, that was not your problem.
Thanks for the comment. I think the one bad cap could have been the problem. If it was damaged and arcing internally at full voltage, it could have been like throwing a switch, causing spikes. It was the only damaged part I found other than the 1 ohm cathode resistor. But it's possible the previous set of tubes caused the resistor to blow and my gator clips on my load blew the HT fuse both times. I burned in the amp for another hour or more last night and played the heck out of it...no issues. I plugged into the 412 cab with a proper cable this time. You could be right, but I'm not convinced.
Good video BTW
I saw the Pawed Gretch give back and i cant find tat video ? Alougth , it broke my heart that guy iz a REAL DEAL MUSICIAN ! A real musician helpz other musicians ...If they can It reminds me of the. SG i lost that i bought the nite before i lost .my. Wife ...some of her last wordz to me were I luv tat guitar! And so i to all the plastic bell, pickgaurd, and rear electronic plates and those were chromed also...i kno dont hav. Any thing to do wit tiz vid, but I wanted to tell ya my story I am a poor man by all mean z ...but maybe Some day i will get another 2015 cherry sg or other year and memorialize it for her.. I luv ya repair vidz they ARE my fav videoZ ON here im not bad tech but watching you teachs me tingz i didnt kno as good az i do now im 1 of ya biggest fan z .....But the Guy ya showed reuniting him wit his Gretch guitar brought a tear. ....To my eye.. Thx for all ya taught me regards Shaun
I prefer the Marshall MG 100FX And the MG 100HDFX over DSL yep I sure do..i also have JCM800 and JCM900..never played out of the 2000..
have a 30 yr old Peavey VTM60.Tube amp. It's the Peavey that marshall wanted the 800 to sound like. LOL Never had a problem with it. I don't see any on the web having such trouble like the marshall's and Boogies and... UA-cam is full of "top of the line" tube amps being repaired. I like tube amps but I will never pay the price for the newer ones knowing how they're put together.
Run Bias Run.
The board could be a blem board assembler at Marshall had on the shelf for a while. They were in a rush to move all these amps out of the factory for their newer counterparts called DSL which is the same as JCM 2000
I've read the second generation DSL100 from 2017 early ones that replaced jcm 2000 last years 2000ish suffered same issues. But the newer 2018 DSL 100's are way better Marshall fixed all the issues from customers complaints & added a few new features.
Does the JVM series have same issue, Bias runaway?
I hope that you got paid real well to work on this monstrosity-that-wants-to-be-a-Marshall amplifier. Just sayin'...
Oscilationis the problem.You must place 1k resistor close to tube socket on input of each tube just in line with input and 470k between same resistor and earth, and tube should quiet down and bias should be set to 33ma each tube for aprox 450volt. If above 500volt then max 30ma..
Another amazing video. But like your Boogie videos, what an over complicated piece of shit! I'll stick to my 78 JMP 2203!
I think Marshall needs more wires in their amps. Nothing is more impressive than a rats nest of colorful wires. I'm working on a Fender Cyber Twin that likes to blow the PS fuse for the digital circuit. Doesn't look like it's going to be nearly as fun as this Marshall, though. ;) Cheers!
I have been watching you for a few years now and you've not only inspired me, I get allot from you're electronics knowledge and guitar playing, I play and I do work on electronics as well. Back in the 80s i worked on VCRs and stereos etc, I played music as well.(in church). During those years electronics was only a side job and I had to stick with working with my dad in house exteriors...... not quite my interest but I had to make a living..I started a small recording studio and I did pretty well with that but that was before things went digital and folks could buy software for their computers lol... Long story short I recently got back into playing and singing and working on radios and amplifiers... pretty much had to repurchase equipment over the past few years, lol Thanks so much for your videos Brad. keep em coming when you can..... prayers and blessings, love and peace, safety and prosperity for you my friend God bless!!
Thanks Charles. God bless you too, and good luck in all your endeavors.
The Guitologist thank you my friend.
When the fuse blew it sounded like you dropped something nearby, causing something in the tube to rattle and short out causing it to spark. I'd be suspect of that tube, give it a few taps to test.
Your patience is beyond mine.. I owned a Marshall once. Hahahahaha..
About now.. Iwould be in the bottom of the hudson river at this point... 36 MInutes in
It be parts. Or sunken..
Hate modern shit even though I own some. But I won some old shit too.
Used to own very old stuff I wish I never sold now. They have turned to gold.
Screw the DSL. Mine fried a tube that took out some resistors and a tube socket with it. But I did enjoy your troubleshooting. Mine was screwed up as bad as this one. I love working on my hand built plexi clone compared to the DSL or HVM.
I had another one of these to check over couple of weeks ago and one of the screen resistors had fell completely out and was rattling around in the box !! Hahaha great soldering they did....
I had this same head, worked fine until it didn't...left it at a repair shop for two months, they couldn't find the problem...another shop quickly found it was a faulty fuse holder :(
Another idea. Why did the tube spark? Could there have been a nasty quick burst of parasitic rf happening? I have been known to add screen resistors in amps where they were absent and increase their value slightly in amps already with them. Also any screen or grid-block resistors must be as close to the tubes as possible - preferably right on the socket. And I never use anything less than a 1-watt power rating cuz the little guys are too fragile. Besides we are dealing with high voltage, and bigger resistors resist high voltage spikes better than small ones. In my lab where I operated and maintained a 2.5 mega volt van de Graff we were always concerned with resistor spike voltage ratings too, besides their wattage.