Easy Fix Made Difficult - Marshall JCM2000 DSL100 Repair
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- Опубліковано 5 сер 2024
- This Marshall Dual Super Lead head came with a customer complaint of "glowing tubes but no sound". Our worst fear is that the main secondary of the power transformer might be shorted or open. This would require a replacement transformer. But the actual problem may be even more puzzling.
- Наука та технологія
UPDATE: I contacted the customer on this and he told me this amp was lent out to a friend or family member and it had failed while in their possession, which is just typical, isn't it. He also said when he finally got it back from this irresponsible person, they had left the head in the trunk of their car for about 6 months bouncing around in all weather conditions. That would not have caused a fuse to blow, but god knows what other idiotic things this person did to blow the fuse. Let this be a lesson to you all...NEVER, NEVER, NEVER loan out your gear to friends or family. Just don't do it. Make it a policy and stick with it. The only people who loan out equipment are those with no expectation of getting it back in the same condition in which it left.
The Guitologist that's how mine was messed up lent it to someone to record with it and gave it back with no sound lol lesson learned
This can be solved using the Glenn Fricker principle, which is:
Whenever someone asks to borrow equipment from you, you ask them: "Can you afford to fix it if you break it?" and, if the answer is anything but a clear and assertive "yes", you don't lend it. Simple as that.
Absolutely true El Guitologista. A lot of musicians have this thing among friends and family that if you loan them an instrument, you're basically giving it to them. My son loaned a bass to a friend, the friend moved away, took the bass. Gone forever. I loaned my 1979 Fender American Stratocaster (a very bad year for Fender quality) to the person I trusted most and it came back with a big chip out of the paint, down to the wood. No fault of his, defective finish (air bubble!) but it happened the ONE day HE had it! Weird, but that's how that stuff goes, over and over.
I've done it twice. Both times there were issues with the amp. Never again! They were cheapies. All I have now is good stuff. Those amps will not leave my possession until I die. Then my grandsons will inherit them.
Or there's the one someone loans guitars/amps/pedals etc to a mate they thought was the coolest guy, and then they have a falling out and the guy doesn't get his gear back because they're not talking anymore.
I am a certified Marshall repair agent here in the UK. Check the soldering on the HT fuse holder and the mains fuse holder. Its quite common for these to become a dry joint and need resoldering. Had it maybe 10 times in the last 4 years - so worth checking! ALSO make sure the wire wound resistors do not 'move' when you wiggle them slightly as these can also go the same way as the fuse holders.
I chopsticked every component within earshot of the HT winding down the line to the output tubes. Nothing triggered a fault. Thanks for the comment! I believe this was just a case of a voltage spike or a momentary brain fart where someone maybe tried to hit that first power chord with no load. Not sure, but I saw nothing amiss anywhere.
If we suppose that the fuse is original, is it possible that it blew on its own after 20 years because it was used beyond the maximum design spec? It was rated at 250V but was subjected to something like 330V-ish (before rectifying)?
Marshall allow for this when designing/specing.
Also it could be valve bases on these - you can have an amp on soak test for 12 hours then suddenly something arcs and you can blow a fuse.
I do not come across many valve amps that blow fuses for no reason.
Well - a lot of time customers do not tell you the truth ! For instance - they ran the amp not plugged into a load.
Arcing! Yes. My son's 2015 68 Custom Fender Twin started blowing the internal fuse. I thought ARCING! First time tech said 'twas a bad PI tube. Nope. Second time said put in the 125 v fuse instead of the 250 v. Nope. New tech changed the fuse holder to different type (increased isolation). Yup. Arcing.
I have just sat and watched a whole heap of your videos and I have literally no clue what you're talking about most of the time lol but I find them very interesting and informative and will be watching all of them in the future!
@Michael Steven FriedlanderI'm not sure that's true.
@Michael Steven Friedlander prove it, prove how hes been able to successfully repair many amps with no clue how to work on them
Why would anyone give your videos a thumbs down,? You do a great job at explaining and you make great quality videos. Thanks for being on UA-cam I enjoy the knowledge that you share with every one.
Thanks, Rich.
Glad it works, I still learned something. Been watching Uncle Doug and your videos showed up in my recommendations. Awesome.
Glad to have you, Justin. I go way back with Uncle Doug videos too. He's the man.
The Guitologist Uncle Doug was my first in the ampoholics world. Your approach is a little different, but just as informative. Hell boy, variety is the spice of life! We do see more of your posts. Uncle Doug put out a plethora of videos, all are gems! Just like yours! May the amp party continue! Thankz
Very timely! I had the same problem with a Hughes & Kettner Statesman Dual EL34. I found that the same fuse was blown. Many thanks!
I had the "Bias drift issue" on DSLs before. Was told by a Marshall rep that boards from 1997 to 2003 were made of a material that becomes conductive. In 2003 they changed the material those boards are made of. That's why we see pre 2003 JCM2000 going for pennies on Ebay.
Just subscribed. Great channel.
chungaleta1234 Yep. I refuse the JCM2000 DSL/TSL models in my shop.
I hear you. They are my favourite sounding amps. Bt they sure are a pain in the behind to repair. What I hate the most is the layout and the many boards they have, it is almost impossible to make readings when the amp is alive.
Been there, two times, one did the mod (pain in the ***) and the second one got a new board from UK, best way to fix it. Now got a rocking amp! and resolder most components, everything was getting loose...
The JCM DSL 50 watt'ers didn't have that issue. Only 100 watt versions. I have 50 watt version and no issues ever
I LOVE your videos. Thank you so much for taking all the time to create these. You are a very good teacher.
I'm a horrible teacher. I curse and I forget power plugs. A good teacher is Uncle Doug and his dog Rusty. Those are the real teachers. Compared to them I'm just a bungling hack.
I must be a fan of bungling hacks..
Between "Uncle Rusty" and "Brad the Bungling Hack" I"m learning stores of info. Many thanks for the vids and effort to make them!
Having fried the output transformer of a JCM900 due to totally mismatching the outputs I had a bit of a giggle at the early part of the video. I spent >50% of the cost of the amp on fixing that one, oops. DSLs are great amps, I personally went in a different direction but I'd love one of the DSL50 heads.
Really enjoying this channel as a gear nerd who has, unfortunately, had to have had a number of tube amps sorted out... some of them by tech who may not have known what they were doing even though they came well recommended!
Oh, and you're a serious guitarist going by your previous videos. Awesome.
EDIT: Wrote this 1/2 way through the vid. You broke out the chops at the end. Love it.
damn this video saved me my head was down today I saw all the tubes glowing no sound so I youtubed it and found this video.changed my fuse and it ran again thanks so much saved me a trip to the repair shop!!and of course someone else was using my amp while i was not there.
Just wanna say, you essentially have my dream job. I would design some amps on the side, but repairing amps, guitars, and pedals is something I'd love doing for a living
Do you have it yet?
I REALLY enjoy your videos! Your instructional style is as professional as I've seen. Your approach to troubleshooting is spot on. I've learned a bunch watching your videos. Thank you so much!
Also, thank you for not trying to be funny. I hate it when the host of an instructional video tries to be "cute". Besides, the AC cable part was plenty funny enough! Nice to know someone else besides me does that sort of thing! Cheers!
haha, thanks man. Well, I do get silly at times when the spirit hits me, but yeah, I tend to be all business most of the time.
I know this is an old video now but I thought I'd let you know that one of the most common issues with both the DSL & TSL 100's is the 16 Ohm socket.
It switches the other two off when in use but when used with 8 and 4 Ohms the 16 Ohm socket cooks up and goes O/C.
I replace it on sight as it can cause the output TX to fail and more commonly blown HT fuse from back EMF from the O/P TX under no load condition or obviously damaged valves.
Pull the harness back and you'll see the earth terminal is cooked up.
While you're at it, reflow the effects sockets and the 5W resistors for the +/- 15V supply.
Regards from the UK 🇬🇧
Great vid. Love seeing a guy who really loves this stuff do his thing. I actually learned a few things. Bet your swamped with work huh? I have a pair of Hiwatts that could use your attention. One Biacrown, ( I freakin LOVE that amp )the other a Hylight. I also have a Fender twin that burned three resistors in a row on the effects board because my son left an uncovered "one spot" plug resting on the tip of the cord that was plugged into the return to the effects loop. Cant find anyone local to check the board to see if the traces burned, or just the resistors. Keep up the good work. We need an amp guy like you around here!!!
Well the shipping on the Fender would KILL you both ways, but the Hiwatt might be doable. Hit me up in July when I begin taking in outside work again. bradlinzy at gmail
Gotcha. Not worried about the shipping, it has to be sent somewhere anyway, unless I want to just try to jump new resistors in their place, but lets face it, since they burned, it really needs to be diagnosed. The Hiwatts just need to be diagnosed, and see what needs to be updated to keep these babies cranking for another 40+ years. Thank you my friend, keep up the great work.
Hi Brad. I love your guitar noodling. Fast fingers Freddie! What was the bias on the valves?
Brad, I think one thing that sets you a part from other techs, is you have a practical approach to what you do! Some techs would have to hook up a sine wave generator and a dummy load and an oscilloscope. You have to sometimes but just a guitar cord and a speaker can be very effective in the troubleshooting process. I have used that simple method for as long as I have been building and servicing amps and guitars. I have a 1-12 JCM 800 Lead Series with 6550s instead of EL 34s and I am debating whether to convert it to EL34s. Tube wise the EL34s may be a bit cheaper to replace, the 6550s are a bit louder(this amp is too loud anyway) and cleaner. If I alter the tone stack, it could be used as a bass amp. Great video! Hope it don't come back later with some other worse problem! Thankz
If it comes back, it should be for some other fault. I wiggled and prodded every component remotely connected to the HT winding and everything was rock solid. Go figure. I power cycled the amp many times and played through it for a good hour without issue, even with the fast blow fuse.
The legendary - or maybe just infamous - Marshall that does it all. It has the sound of basically every Marshall ever inside 1 amp. It's an 800, 900, and a Plexi plus some metal tones all in 1. But they always blow the HT fuse and basically nobody knows why - and i'm not convinced you have figured it out either but I will keep watching. Maybe you solved the mystery!
Thanks man. Was able to fix my amp in no time (and only for $5)
Any experience with JCM2000s having effects loop issues? Mine will still produce output when the master is zero, and that extra output is very treble-ish, harsh and distorted. Only happens when I'm using the fx loop
Did you like the sound of this amp? I have two Marshall TSL60 amps and I love the tone.
Amazing video!!! Thank you so much!
I'd have to look back at the schematic to see if the thought I've had would carry any water, but I watched this early this morning and I guess the conundrum has been ticking away in the back of my head. I recently repaired an unusual rotating speaker setup of a friends with a separate preamp that was blowing fuses and I found the source of the issue to be a relay stuck in an energised state. Different scenario and problem but I was just thinking about the way that channel 1 sprung into life as you brought it up. Anyhow.... Hope the weekend is being good to you sir.
I've got a similar issue but the mains fuse keeps blowing. Without a lot of knowledge I think it's due to the power transformer as I'm only getting 5.6ohm across both primary coils as it's wired for 240. But this would give a current of about 42 amps. Do you have any recommendations on something else to look at/test?
i recently blew the mains fuse in my Laney LC30, by putting in old Mullard EL84 tubes, turns out they're wired differently to current EL84s and the Laney can't handle em. since then i can't get any sound out of the amp with previously good tubes (jj), also replaced the output transformer thinking that was blown, not sure what is wrong!??
So, I just got a new(used) Marshall Lead 100 Mosfet head and was wondering if you could service/modify some things on it for me?
My TSL100's clean channel has a loud constant hum and the volume knob does nothing but turn the hum volume up. Hum is present and loud even if volume knob is on zero. Somehow all the actual clean channel volume is from my gain knob now; even if the volume knob is on zero turning up the gain gives me huge volume albeit with hum. Do you know what is causing this problem?
Hi I have the 50 watt version. I love my JCM2000. However since using a noise suppressor in the FX loop I've realised the built in reverb must be pre FX loop. Which means the reverb tail gets unnaturally cut off when the noise gate kicks in. This is a real shame. I know the work around is to use a reverb pedal however I was wondering as a circuit man,, can you confirm this to be true, seems odd to have reverb pre FX and also is there a mod I can get to change this? Thank You.
Perfect timing you have, my TSL 100 is in getting new tubes. I'm watching your videos and missing it. BTW what was the bias?
Hi.
The HT fuse went on my old 74 superlead when I used a 4x12 with a blown driver. Only ever goes then. May be that the family member was using the wrong ohms for the cab and it blew the HT. Anyway, really enjoy your channel. Lots of fun stuff most of which I don't fully understand yet but you're teaching me lots. So cheers.
jcm 2000 dsl 100 input jack problems , intermittent full power too real low , have to turn the input jack sometimes ?
Is it okay (with rebiasing of course) to replace the EL34 tubes that a JCM2000 uses with a set of KT77 tubes? I've heard they're interchangeable but I would want to know for sure if it would be okay before I ever tried it.
I wonder why the HT fuse is rated for only 250 Volts as the HT supply is likely around 400+ VAC. Do they use a smaller rating beecause arcing inside a failed fuse would be less of an issue due to it being in the AC part?
I have a TSL that has a problem in the bias, but different from the other TSL that Bias goes up until the amp collapses, in my TSL the bias goes down to close to 2mv and then goes back to normal 80mv. This happens sometimes and lasts a few seconds between descent until normalization. Any help?
Thank you sir for your video, but you really got me on your Guitar, ( love your pic'n )
Thanks Steve!
Marshall 1960A and B 4X12's have 16 ohm drivers and can go either 4 or 16 ohm. I always ran mine 16 ohm, but some guys run 4. That might be was this guy was doing. I had a TSL 100 from 1998 and I had to replace the main board when mine started having the bias drift issue. It never sounded the same so I sold it.
At 5:32, I noticed the white (W11) and white-grayish (W13) wires from the transformer to the W11 and W13 on the board. On my exact same amp, someone worked on it and reversed the wires to where the more true white one is going to the W13 terminal while the off white one is going to the W11. Will the reversal of these wires make a difference? Thanks for making the videos. They are very helpful.
Now THIS is the amazing content that I freakin' miss & love my dude. Just sayin'.
.
The British call voltage electrical tension. HT= high tension = high voltage.
Thanks for pointing that out. You're right. I think I failed to mention that. I've always viewed voltage potential are more like a waterfall. How high is the waterfall? It's x volts high. The waterfall itself is formed by resistance.
And the amount of water over the fall is (literally) the current.
I've always liked the water main analogy. Water pressure is voltage, amount of flow is current, and the pipe diameter is resistance.
@@TheGuitologist in electrical engineering, we had a class where we modeled water distribution and mechanical systems as well as electrical circuits. You guys are spot on. Voltage is Pressure, current is flow and reservoirs acted like capacitors.
In much the same way that American celebrities call extra-judicial murder a photo op.
Marshall cabs have a duel input that allows for 16 or 4 ohm mono and 8/8ohm stereo. Have always run mine in 4ohm if the amp is capable.
Totally. No one seems to know this. Rehearsal rooms are full of them. Folk think that if the switch on the cab is to the right and plugging into the right hand input is 16ohms. It doesn not. Its 8ohms. Hence why many use the 16ohm out on their amp. 16ohm out into 8ohm input = DISASTER.
Switch should ALWAYS be to flicked to the left. That way the right input is 16ohms and the left if 4ohms.
What is the capacitor C2 doing in the HT High Tension circuit? What is C2 filtering out
I have a Marshall JVM1 1 watt tube head with an intermittent volume reduction problem. Amp plays as it should, then suddenly drops down very low in volume with random static noise.
Replaced every tube, desoldered tube sockets and then resoldered with nice shiny fillets. Still randomly low in volume or good, depends on its mood. Problem happens on both clean and gain channels. Tried checking for loose connections. Thought transformer leads were loose, so I soldered the wires onto the transformer terminals. Jumpered effects loop. Cleaned all jacks.
Called Marshall and they said to signal trace it. I'll need to get my scope out of storage to do that. Guess I might need to go that route. I was able to get a schematic for the amp. Thought output transformer might intermittently be shorting and causing volume drop. Marshall tech said to check the low wattage switch. Still nothing. Even touched up solder to most of the components.
Baffled? Heaters remain glowing. Checked high voltage and had 240vdc. Need to take voltage readings on all tubes when good, then again when it drops volume.
Any ideas?
hey would you be into modding a marshall mosfet lead 100?
It's less stressful that way right?
Brad i have this amp. The chasis and Trannys have some surface rust how do i remove?
i have a TSL102 that did the exact thing to me. when i first got it i did a stress play test and it popped its main fuse.
I checked everything over three or 4 times and couldn't find a smoking gun. I put meters on the bias voltages monitoring them looking for bias drift. Ran it for a few hours and nothing. solid.
Just waiting for it to happen again. :(
I have seen tube era Ampex boards, 350, 351, etc, turn conductive on the surface. You have to pull all the parts and really scrub them with Scotch Bright.. Same thing with blue and brown board version. Real pain to restore those when the boards are goofy.
I almost bought one of these. Got a quick one, how do you tell which is a good one of these JCM2000s and which is well, garbage???????? I seen a few in Guitar center simply not have any sound come out.... Also one EL34 simply loose power or illumination out of no place.
I fully realize I may not get a reply (haha) but Brad, I have a Marshall DSL40C that’s just over 1 year old. I love the UltraGain channel and have the gain around 8. It started making this intermittent huge volume swell with a high frequency squeal followed by a nasal tone. This only happens after 15 minutes of playing and the amp getting warm. I replaced ALL of the tubes, biased the EL34s but it does the same thing minus the high frequency squeal.
The Marshall service tech states he finds no problem and the issue is that my gain setting is too high.
Other DSL40C owners had the same issue and supposedly found a faulty blue colored capacitor.
I tried to point out to the tech that C25 has black residue on it but he claims nothing is wrong.
Does this sound like an oscillating circuit or a negative feedback issue?
I realize it would be difficult to even comment on this but I thought I’d try.
I’m picking it up tomorrow and trying another service center.
PS I can recreate the symptom by simply adding a loop pedal in the front and 10 minutes later it shows up.
Thanks and if you don’t reply, no worries.
I've heard this amp fails, something in the desing of the PCB, I want to know if marshall corrected it and what years of production are safe to buy, please.
I think they changed the pcb in a revision at some point. Later versions of this amp were less likely to have this problem and even most of the early ones did not show any problems with this.
I think you can buy a diy mod from amp parts uk for runaway bias syndrome....👍
I’m surprised no one has commented “a blown fuse is the symptom of the problem, not the fix”.
I realize we may never know now but if that’s really all it was I would be curious as to why it blew.
And if I’m the customer, he didn’t even try to simply replace the fuse? Before paying shipping costs and repair costs I would at least try the fuse but again, I would have guessed it would have blown again. Apparently not in this case I guess. Very strange.
what model of Variac transformer you are using .. thanks
Also look for the note... If you look really carefully at the back of the amp where 16, 8 and 4 ohm jack outputs are located. It will read "Note: 16 Ohm Output Jack negates use of others." You can either run a 4 or 8 ohm load single output or parallel two cabs together. For example two 16 ohm cabs ran parallel then you set it to 8 ohms and plug in each cab. I always just ran mine with a 16 ohm single cab and at that point it makes no difference what the 4ohm/8ohm switch is set to.
I had some issues with my Marshall DSL100, and symptoms were different, i was losing my tube glow. It was intermittent, amp would work for a while then go bad. Infuriating. It turned out the wires coming from transformer had a whole bunch of spade connectors that could not grip onto the lugs. Totally loose. So they were in place, but the connection was literally just metal touching metal, no clamping pressure. I just got some pliers, squished the spade connectors to close them up a little, then push them back onto the lugs and hooray they gripped tightly. Problem solved.
In your case, you haved glowing valves so obviously the circuit to your valve heaters is ok, but i'm just wondering if your issue might've been some loose spade connectors on wires going to the high-voltage side of your tubes. I don't know much at all about tube amps, but what i do know is my amp looked like it had never been worked on, those spade connectors were loose from the factory, and I had half a dozen all loose as hell. So, loose spade connectors can be a dog of a problem and i guess depending on which ones are loose they could cause a variety of issues.
I have a tsl 100 head.bought new mother board, but still bad volume.resoldered everthing. Input was lose and now works great.
Hey Brad! I have a JMC 2000 TCL 122. The main pc board is the version 5 of this amp. Marshall has stated the epoxy they used becomes conductive over normal use. I also know you mentioned this in the video. Does it just become conductive around the tubes and the high voltage or all over the board? Is it worth trying to fix the board? What blows out when the bias goes nutz? Any suggestions? Love the videos. Keep it up!
If your bias goes out of wack, worst case you risk blowing the primary winding in the output transformer which means $$$..not to mention killing the EL34's. The main PCB can be modified to overcome the problems with board conductivity and bias runaway as i have done it successfully, but i dont recommend doing it as it quite involved. Unless you are experienced in valve amplifier repair and well versed in its operation dont even remove the back cover !! Have a new board installed by a experienced tech...these amps run at DC potentials of 300volts plus and can kill !! They are extremely dangerous to work on...Do NOT run it without the recommended rated HT fuse installed....
I'm not sure if you've done this yet but going through hundreds of videos, trying to find it's a pain in the ass. But I have a Marshall mg100hdfx makes a god awful super loud noise when turned on. It also makes a loud pop when turned off. This happened out of nowhere ands only few years old. However if I unplug the cord to speaker from the head and then turn it on and put the cord back in once on it's good to go. Trying to find out what the hell is up. It still works fine and unplugging and plugging back in works but id like to figure this out regardless
I like that you demo'd it through a potato. You know, just so the mystery of its tone can remain as-if through a veil.
Just got a Laney head today, tubes glowed but didn't make noise. Think it might have been damaged during shipping. Thoughts?
Tanner Hoyt Check the fuses, then the tubes to see if any are dead or loose, then the output transformer with an ohmmeter (amp shut off.)
I have a JCM 2000 401 which is just the 40 watt versos! I had to have it serviced but she's been ok since then, so watching this in interesting to me.
and I just looked, mines a 2002, I got it used.
I have a jcm2000 401 combo which are known to have a problem with overheating. Would the 50 watt head have the same overheating problem?
no. The DSL 50 is the best one they came out with. Jeff Beck used one for years
I'm wondering what connector W12 (7:00) is for, and why it isn't connected. Enjoying your videos!
Great upload, +1 sub!
I'm really looking into buying one of these amps. Any tips/things to look out for? Also would you recommend I don't have it shipped to me?
Big Sauce Persoanlly I would always pick an amp up yourself if you are buying it. It means you get to try it out and make sure it works before you buy it etc. I've had a few bad experiences with getting Amps shipped to me, so I'd say it's more trouble than it's worth. That's just my personal experience though.
@@wastewoodrockers5526 noted, thanks allot.
The DSL sounds great, but the models made before 2003 had some issues. Try to look for DSLs made from 2003 on.
I am going to guess the fuse blew because the speaker load didn’t match the 4 ohm output on the amp he had it set on. It’s important to get your calculation right. Matched speakers parallel is half the impedance and speakers in series get added together. So many people fail to calculate properly with multiple speaker cofigurations.
HI Brad, HELP!! I have one of these thing except the 100w TSL version and it makes like a farty oscillating sound on the clean channel? Whats up with that?
Any help or advice would be greatly appreciated as I got this for AUD$500! Usually it costs $2,500 over here so id love to get it working well. So far all I have done is use some contact cleaner in the jacks and switched etc on the front of the amp. That seemed to work for a little while, now its back and really pissing me off. I am reluctant to just put new tubes in it and hope for the best?
Here’s the problem: one of your phase inverter resistors popped from a voltage supply surge. These are the resistors on the plates of the last 12AX7.
Dangit it's only a stoopid fuse Brad? And I was hopin for piston stickin out the side of the block! Too easy! Maybe the next one!
I find myself intangibly unsettled by having Johnny Cash watch me watch you test driving this Marshall....
I've had impedance switches fall to bits on Marshalls and Peaveys in the 2000's a few times. They were very different types of switches. I don't think they were made by the same company. The PV amp and most of its parts were of Chinese manufacturers. The Marshall I don't recall, I just assumed that some parts came from not England even if the amp was.
tag with Year of manufacture also has end of warranty period?? 2007 maybe?
That is some tone Brad... xx
not sure if this amp is turned up all the way or not, but it doesn't seem to have the quality of the older amps you play.
What amp tubes does this amp use? Thank You
DMR Productions thank you
I love a reverb that activates a week later 😂
Fuses can just burn out naturally sometimes due to age the fuse wire just gets weak. Just the same as lightbuilbs blow.
thanks for the video ``I just love the sound of a marshall...question ,w\hat gives the different amp brands their signature sound? power tubes? pre amp? a mix of both? type or capacitors?...I see p[people make marshall clones but they don't seem to sound like the marshall they were cloned from, same with Fender amps ...or is that just my eras fooling me because I see the brand name and associate it subconsciously with a sound, thanks
A lot of it is the shaping of the tone in the preamp, V1 stage being most important, and the tone stack. People often cite output tubes as a major factor, but it's less important than tone stack, and even more specifically, the amount of midrange frequencies are expressed.
I think there are also fuses on the circuit board
How come you were measuring DC voltage on your meter? Shouldn't the output of the transformer be AC?
Prehistoricman - The Transformer transforms A/C current into DC, which is what the rest of the innards use. A/C is used for long distance transmission for reasons of safety and efficiency, but most gear really needs DC to run...hence the Transformer. Thank Nicola Tesla for all the cool stuff the A/C system + step-up transformers (not to mention resonant transformers) gives us!
The AC output from the HT winding on the transformer is rectified to become the DC on the HT line. Finding DC on the HT line shows that the HT winding must be OK.
Buy one like this or build an amp?
How did you learn how to do this, I must know 😭
The hardest diagnosis to make when troubleshooting anything is that there's nothing wrong.
If his marshall is like mine the stereo selector box in the cab is dead and hes had his cab hardwired and had to use 4 ohms
My suggestion on all amps esp NPF ones esp where fuse blows for apparently no reason is to tap the power tubes to see if there are any warped elements like the grids that might sag and short to other elements when hot under stress or even cold sometimes.
I've had many tubes that like to behave until they're physically 'challenged' (;- ). Also true with prank tubes...
Marshall cabinets can be used in either 16 ohm or 4 ohm. I use mine single cabinet at 4 ohm.
These DSL series amps suffer from dry joints worse than any other amp I've worked on in 30years. The interconnect wires between the PCBs usually need resoldering . The bias supply caps always need replacing too.
Negative good buddy.
I couldn't disagree more...
Over 400Vdc for a 250VAC fuse?
Yep. I don't think anyone makes a fuse in that size rated for tube amp plate voltages...or with a DC rating. I know it makes a difference, but it's commonly done.
The dsl range is notorious for blowing the high tension fuse.
These look like a nightmare to work on. I am absolutely shocked there is that much going on in that circuit. I bet the JVM looks ten times worse.
Dude you play guitar Right Handed !! Don't poke your left hand in the Amp Ever !!!
I understand your fear. It's probably good advice. For the record, I'm not really putting my hand in the amp when I'm pointing. Most of the time I'm hovering way above the amp and just pointing. I've noticed sometimes it looks like I'm almost touching components, but it's an optical illusion. Moving the probes though, yeah, I'm not into shutting down the amp every time I move probes. I appreciate your comment, it comes from a good place.
I think that the design and component selection is marginal on those amps, I know that the main power transformers work hard and normally run quite hot, combine that with a 1 A fuse that should probably be a 1.5A fuse, I have had to replace power transformers on these amps, so I believe it is just poor choice in component selection.
The newer 1960 cabinets have switching on back for 16 or 4 ohms mono and 8 ohms stereo. I use mine mono at 4 ohms. Much beefier 🥩
This is all making me afraid to risk buying a dsl. Though these are all older
I'm betting inside a brand new one it looks about the same. Anything from the 90's isn't really that old. The boards are the problem in any modern amp which 90's stuff is. Not much different than today's. The really old ones are all hand wired and much easier to fix. You want an older one. This one wouldn't be considered older. Even though it's over 20 years old.
If you dont have the ohms swich right it will blow a fuse or a tube every time
If one is using a 16 ohm cabinet with that amp, the position of the impedance selector switch is irrelevant. It only applies when one is using the "4 & 8 ohm PARALLEL JACKS".
YA FARGOT TA PLARG IN DA POWA?! THAT'S AN EXECUTION BACED AFENCE! LOL LOL
Johnny looks irritated. Maybe he needs a sunnier wall to lean on.
The Man in Black feels right at home where it's "Dark as a Dungeon". ;P
Well, I think he mended his ways since those days. Rosanne says he and June used to sit on the back porch all day. She would sing to the hummingbirds, and they'd hover right in front of her face while she did. Now, _that's the life! Hey, if you want to hear something great, search for a video of the Carolina Chocolate Drops (and all black string band with a female lead singer who's incredible) doing their version of "Jackson" for the PBS Johnny Cash Tribute a couple of years ago. Best version of Jackson you'll ever hear.
U didn't check the bias, these amp have a bad bias drift. It would pop a fuse if the bias drifted high. They need new boards to correct this. So HE'LL BE BACK!
I love your videos and I want you to be making them for a long time, so can you please do me a favour? Keep your fingers away from the death-inducing spots inside the amp. I know you know, but it still makes me nervous watching. You are so close to that live Standby switch. At least wear non-conductive gloves. If not, can you please leave me your test equipment and spare parts in your Will, and I'll arrange the shipping to Australia.
We only have 120V here in the USA 😃
@@Twobarpsi HAHA! I get it....Aussie 240VAC will kill you twice as fast as USA 12VAC. 😃I'm even more concerned about the Voltages on that Standby switch, which are common to both counties: a heart-stopping 450VDC. Brad is a lot younger than me, so he may get to complete my "Oh Shi..." gurgle as I fly backwards across the room.
@@lestelie4410 would 450V DC arc across an air gap?
@@Twobarpsi Sure it can. It depends on the air pressure and humidity and the distance between the 2 surfaces, eg the back of your hand and the Standby switch terminal. I'm pretty sure it is called Paschen's Principle, but we could rename it "The Guitologist Principle", and wait for Brad to get close enough to create an arc. LOL! (Only kidding Brad. I only have love and respect for you).
I got sucked into buying one of these glorious pieces of shit from a pawn shop for $600(ca). Thought I was getting a wicked deal. It turned on and made sound at the shop so I bought it without really giving it a good tryout. Well 20 minutes into my first set with it the fucker started to cook... LOL Had to replace R7 and R8 resistors. Oh well, I dumped it at another pawn shop for $500... Lesson learned, if it seems too good a price, there's probably a reason... LOL Been using an MA-50h going on 3yrs.
the JCM2000 DSL 50's are a bit more reliable . Dont have that Thermal runaway issue like the 100's and TSL100's. Some solder joints need to be inspected and re-wetted for good measure, but mine is behaving itself.
I know the likelihood of you reading this comment is very very low. But here it is, I have a marshall jcm 2000 dsl 50...... All of the comments online made by repair personalities who are always talking about the JCM 2000 bias drift issue make one major flaw in their statements.... THE AMP BIAS DRIFT ONLY AFFECTS DSL 100s and TSL 100s made prior to 2004. The issue that is created by just saying the jcm 2000s have this problem is that people believe the other 4 or 5 variants of the jcm 2000 series amps have the same problem.... THEY DO NOT!
Thanks for making me waste my time trying to look and see how much a replacement pcb board that doesn't exist for a problem it will never have as it does NOT even have the circuit!!!!!!
Where did you get that information it only affects DSL and TSL 100s? You don’t know that.
@@TheGuitologist either you or about a half dozen other amp techs are wrong. Apperently the dsl 50 which I own does not even contain the affected pathway, this I discovered after looking to see how much a kit to fix the motherboard should it go bad would set me back. There are only kits floating about for tsl100s, and dsl 100s. So I started looking at other forums.... And there are a lot of other techs saying that it only affects the 100s made prior to 2004. I would give you a link or two, but that was over a very very long bad week ago for me, and I just don't have the energy to try to retrace my steps at the moment.
These kinds of things always give me a less than great feeling to send back. That fuse didn't look like it went from stress, but a major overload. Short of customer abuse, I'd be afraid that there's still a gremlin in there I failed to find that will come back and bite me. But if you can't find it, you can't find it. You have to move on.
I poked around on every component associated with the HT winding. There was just nothing to go on, no indications of a problem anywhere. I might have said "bad solder" or something, but chopsticking everything revealed nothing. I can only do so much for the bench fee. Pulling boards would mean more $$$.
Oh, I fully understand. And while some of that may be part of your normal checkout, I suspect you had a that uneasy feeling as well - or you might not have spent as much time looking.
Besides, even though it's quite rare, some fuses just give up even if they're nowhere near their rated capacity. It's what happens when a device is explicitly designed to fail.
@TheRedneckAtheist, true, but in that case the fuse just has a crack or has melted ends. The one in the video was blackened. It died violently - apparently from something well in excess of it's ratings. If it showed signs of "minor" failure, it'd chalk it up to a weak fuse and move on.
But the fact that a fast blow fuse is stable in the equipment says otherwise. There are other modes of failure that can cause a glass fuse to be blackened and still have continuity, one of them is a seal failure causing oxidation. Another way is a very slight and very brief over amperage that doesn't blow the fuse but strains the filament.
I would never borrow an insturment except for maybe to pass a guitar around the kitchen for a tune and right back
.i dont want the responsability.. its just common sense you break it you buy it
And i cringe a little bit every time somebody asks me to even play mine