Hey guys...thanks for the overwhelming response to this one. I've gotten a lot of questions regarding what was the final diagnosis because apparently I wasn't clear enough in editing. The switching transistor TR1 was faulty. Replacing that allowed the Boost Channel to come alive. The phase inverter tube, V5, was causing some sort of issue as well, as was shown in the video, so it was replaced. It tested good on my tube tester prior to troubleshooting. I edit out tube testing from most videos because it gets laboriously long - 50 minutes even without showing tube testing is getting longer already than most attention spans. In fact, you've probably already stopped reading this. The V1 tube tested on the weak side of good on my tester, but I left it in because it should have still worked just ok, which it seemed to do because it is also part of the Boost Channel which was working before I replaced that tube. The V2 tube was the one I finally replaced at the end which allowed the Normal Channel to function properly and fully. The tube I was using in that position during the troubleshooting tested good on my tester, but for whatever reason, this amp didn't like it. The fact that it tested good on my old Precision tube tester is what led me to assume it wasn't the tube and explore other options. Also, if you'll notice on the schematic, the switching is tied into the grid of V2, which is how the Normal Channel gets muted during Boost Channel operation. My theory was that switching in the IC might have also been at fault. Anyway, hope that clears thing up for those of you who had questions. Watching the video back, I can see why it was confusing.
The Guitologist I have only just started watching your channel but I have to say you are a star sir! I am an electrical engineer in the UK and have done a little bit of amp repair and build myself, but ultimately I would like to have a set up similar to yours. You bring wonderful old amps back to life that would otherwise be thrown in the skip so well done you hero! 😊👍. Love the guitar playing by the way. Just one question about your signal probe, as you are at plate voltages I presume you have a dropper resistor in line to protect the input of your test amp? Keep up the good work I am already a big fan!!! Keep on rocking 🎸🤘🤘❤️🎸
I believe that every repair comes with a lesson; one of those "I should have tried that!" moments. If you took away that kind of a lesson from this, what would it be? (Would it be to break out the chopsticks early?)
EYE TROUBLE I USE CAPS :) . I REPAIRED TVS FOR 30 YEARS AND AM RETIRED NOW . I ENJOY WATCHING YOU AND THOUGHT ABOUT KEEPING MY HAND IN REPAIR DOING EXACTLY WHAT YOUR DOING I.E. WORKING ON TUBE AMPS . I AM OLD ENOUGH THAT I WORKED ON TV'S WITH TUBES IN THEM FOR A FEW YEARS AND RETIRED IN 2005 . BUT WATCHING THIS VIDEO SAYS EXACTLY WHY I DONT LOL - I AM ENJOYING MY RETIREMENT . STILL LIKE TO WATCH YOU TROUBLE SHOOT . GOOD JOB. KEITH
These videos are like a murder mystery! Who dunnit? Well, it wasn't Professor Capacitor in the main board with a leak...let's try Colonel Transformer in the mains section with a short...lol
lol This one was a doozy. It makes you wonder if you should just replace all the tubes in the beginning just to eliminate those as the culprit. I admire your determination and methods of troubleshooting
Then I would not be able to film myself flailing around like an idiot. :P But seriously, those transistors were definitely bad also. And it didn't hurt to change all those caps in the switching circuit.
THe problem with this channel is it's so addictive. I've lost about 6 hours today. Apart the educational side, I just love your accent and sense of humour (I'm in the UK and just love southern accents) . Please don't ever think of stop making these videos. Just wonderful.
Kudos to you! I recently had my amp go bad and brought it to an amp technician who made it well again. Thank God for folks like you who help make things well when they go bad. Great job!
I'm a completely self taught amp tech and I've had a bunch of those "I'm completely at a loss here" jobs. I spent almost a week off and on with a repair of a simple scratchy pots job in a late 60's Univox stencil amp made by Garnet here in Canada. I initially told the customer it would be a quick fix. Oops. There was constant static throughout the whole signal chain caused by one damn 5 cent resistor. I thought it was only me who did so much head scratching. Really enjoy your videos and find them very helpful. Thanks Brad!
She is trying to tell you that British folks never understood electricity. Or maybe it was just the humidity. From cars to amps they showed their prowess.
You mean the Coarse Adjustment Hammer and the Fine Adjustment Hammer I assume... I used to have a large mallet on my bench which had "Coarse Adjustment" written on it in magic marker.
Wow, that was quite a journey. I have one of these amps and after several visits to repair techs I finally gave up on it and bought a new DSL 40. Several years later now, I may open it up again and try a few things, so thanks for the vid!
I blew the dust of this vid that I missed back then. Great troubleshooting! I get more confident about tearing into an amp I accidently misinstalled a tube in and it flamed a bit. Thanks Brad, keep 'em coming!!
Damn, I get too into these videos. I was stressed completely out until you figured out the problem like four minutes before the video ended. What drama!
It can really suck when one has multiple issues. You try your best to eliminate variables but it doesn't always work to plan. I did test the tubes before even starting on this, but edited that out for time. Turns out, the 2205 is really picky when it comes to preamp tubes.
For having no background in electricity except a little DC theory, you sure have whetted my appetite to learn this circuitry and everything with it. Voicing your train of thought sure makes me feel like I’m learning something. Wish I could go to school and start all over again!
I studied electronics in votech (high school)... I passed the classes with a C... I knew then at 17, I would never do this work for a living. I became a Main Propulsion (Steam) Engineer in the Navy... the system drawings were just as complicated but the components are a lot larger, and easier to troubleshoot. 20 years was a life's work. LOL I did follow what you were doing and finding but had no clue as to what was needed. GOOD JOB!
Hopefully it helps someone. I know the clips seem to skip around a bit in this one. That's because it was filmed over several days and some things had to be edited for time, but it's essentially all there.
19 minutes in, I watched a bunch of this guys videos, I know he will get her fixed up and purring just right and he will shredd up a nice storm on it to test her out. This old cat knows his stuff and plays like a pro, don't none of ya all ever doubt him, he is the amp / guitar master! I love this guy's attention to detail and his incredible perception, he's made so many old ratty things sing like a, well a thing that sings really, Really nice...
I had one of these amps years ago and really didn't like it. It had 6550 output tubes that really are not appropriate for guitar. Marshall made their sound with EL34 outputs. Back about 20 years ago, I saw a Crate Vintage Club amp for sale and I went to the seller's home and demoed it. I was blown away by the tone and, after a short conversation, we agreed to an even exchange. At the time Crate was still make these amps and they had a good reputation. I still have the amp all these years later, but it does require periodic trips to the hospital. At this point the tubes have been replaced multiple time and all of the caps were replaced about 5 years ago. I think my problem with the Marshall was having only one speaker - it sounded much better when connected to a 212 or 412 cabinet. Not to give up on Marshall products, years later I bought a JCM 900 50 watt head and traded for a 412 cabinet. I was very happy with the way that amp sounded. I sold it about 5 years ago when I was moving along with most of my other amps, B-3, etc. I don't know why people trash the JCM 900 - I think they sound good for rock. The JCM 800 and 900 can be traced back to the Plexi, but Marshall stopped manufacturing point-to-point wired amps around 1972, so the DNA is there, but not the mojo. I really don't think tube amps are happy using circuit boards where the tube sockets are mounted on the boards, These amps are difficult to service and sometimes impossible to fix.
I have had the 4212 (50W 2x12 Master Volume) combo from new in 1984. It's never let me down and I only work a few miles from the Marshall factory on the rare occasions when I need a retube or a refurb. The last job was new corners, new handle, new Tolex, new fret cloth, new feet. She looks lovely, but still sports some battle scars.
I have a regular JCM800 combo...Single channel, no reverb. Best amp I've ever owned. Had it for over 20 yrs now. drooped in a Celestion Gold 50 watt speaker.....super nice. Recently had it thoroughly serviced...new caps, tubes, and sockets. Hoping to get another good 20 yrs out it. I think I will too. Solid amp
I know squat about guitars and even less about guitar amplifiers, but you made the process more entertaining & engaging than I would've expected...not least with your brief play-test at close. Thanks for the ride!
This was one of you most informative and entertaining videos. Thank you for including all of it! It is nice to see a repair that didn't come easy but worked in the end. Well earned sir!
Oh Brad, man, I think I may have been feeling your pain watching this repair unfold. I can relate to these difficult examples. Well done with the perseverance dude.
Hey Dan, Good to see ya. Thanks for that. It's funny...it's like some spirit is fucking with you and know exactly where your breaking point is. The moment you get right up to the breaking point, they say "ok, let him fix it now".
Dear Guitologist, I discovered yur channel some 6 months ago and really love the way you present and troubleshoot your projects. Having some electronics knowledge myself its very educational and already picked up lot of things I could use for my own modest repairs. Not being able to sent you stuff or make a donation which will significantly change your holiday destignation, which I think you deserve and would like to donate... I choose to express my thanks with..Standing in the Middle of the Street Naked Screaming "LONG LIVE THE GUITOLOGIST"! Not that I am trying to imply that you suck at what you do I wnder if you are aware of this other repair dude on UA-cam... Mr Carlsons Lab. He is something else.. I always go by the mantra..two always know more than one person. No matter how perfect I think I am, an other person with less knowledge than myself can always contribute something unknown to me. Anyways, thanks for your time entertaining and educating us..
The DI is "direct interface" for connection to a mixing console or power amp for larger venues. The 4210 is a great little amp, loud and versatile, killer crunch tone by turning the master all the way up, dial in gain as desired, but will wake up the neighbors.
I just got the 5210 out of the shop. Had to disconnect the reverb circuit off the board because of bad design causing noise. It sounds very similar to this. I have an Eminence Texas Heat 4 ohm on the way to upgrade the speaker and I'll be done bringing a 1985 Marshall back to life that somebody on Craigslist sold me claiming "no issues". Haha $300 for the initial Waffle House pick-up from an unknown man in a pickup truck, $200 spent in the shop and $100 on a Texas Heat upgraded speaker. I now own the world's most expensive Marshall 5210. Still less than half of the price in 2021 than the 4210 currently. Priceless.
Using that chopstick reminded me when I was a kid I was given a neon transformer. A guy at my church was an engineer with Muzak and he told me how the make a "JACOBS LADDER" thingies like in those old horror movies. He told me what NOT to do and warned me to be careful. I followed his directions and after adjusting the distance of the wires it was working. He told me if I stuck a wooden dowel or something non conductive between the wires, the spark would stop there. Only wooden round thing I had available was a pencil. I received a quick lesson that graphite can be "conductive".
I had a 82' jcm800 I clipped the clipping diodes out of circuit , made it into a vintage sounding Marshall. Amp builder Doug Bray told me how to do this and it was awesome . good luck
Watching this makes me glad that the JCM 800 I recently picked up is a much simpler design without all that switching crap, and no reverb (1983 4010 vertical input 50:watt 1x12 combo). It is also loaded with a G12M-65, rather than the 70 in the amp in this video. Mine also has 6550’s rather than EL-34’s. I did spend a bit on a full service to fix some issues (replaced tube sockets, new tubes, and replaced any drifted components). Good as new now.
Remarkable ! Wish you lived in the south of France...I quake with fear when I hand my amps to the local dealership/repair dude... Keep up the good work - with all these tips and ideas I'm picking up maybe I'll be able to pass on the dealer and have a go myself...well maybe not...always a pleasure to watch.
Hi, great detective work. I have one question. What were you using to probe for signal in the early part of the video? Where you put a lead on the grid or plate and it would play? By the way No Remorse is one of my favorite songs to jam to.
My probe was connected to the Kustom practice amp in the background there. Nothing special. Poor man's signal tracer. Yeah, that ending of "No Remorse" was responsible for many a solo mosh pit in my bedroom back in the day! :D
I have had a similar problem trying to get a reading on a negative feedback resistor while in circuit. I couldn't figure out why I was getting such a low value. Then I realized that when the probes were on that resistor, you also have a connection back through the output transformer to ground. In this case, you were basically reading the connection through the 100K resistor in parallel with that 4.7k resistor between the 100k and ground.
Brilliant playing as well as top class repair work. When I did repairs back in the 70's there were very few circuit diagrams available. Keep doing what you're doing, I love it.
I have one and did test the tubes. DIdn't include those video clips in the final edit because of length, but the tubes tested fine on the tester. V1 was a bit weak, but still should have worked. Probably would work in anything but this amp. This model seems to be really picky about tubes.
I have a 4210 on the bench which I had to replace the power switch (melted), replace PT, do a rectifier diode work around because the board was burnt up and all traces gone. Someone did work their which caused the rest of the damage. Amp up working but if you turn the reverb pot it blasts into oscillation. The work continues. Mark
I too had a 1x12 50w JCM 800 combo from '86. Bought it used for $250 back in 1995. Almost from the get-go, this thing had issues: From bad tubes that were rattling, the clean channel breaking up too much too soon (when I wanted the damn thing clean), and the speaker being mounted in a weird place (just lower right of center). Even after getting it re-tubed and serviced twice, the issues were still not resolved. But the REAL FUN occurred when I tried to take it out on gigs. I could never EVER hear it, even with the master volume cranked up. Got bitched at by the band leader for being too loud. So I tried to face it toward the wall. Couldn't hear anything at all, and then I got bitched at for playing sloppily (b/c I couldn't hear myself). Long story short, that amp actually COST me gigs rather than helped me get 'em. Ended up selling it for DOUBLE what I paid for it (hence, what the interested party OFFERED to give me for it), and was only too glad to let it go! I said NEVER AGAIN to getting another JCM 800 after that!
I have always played around with radio and amps. Not so much nowadays. I have been a Bass player since 1965. I enjoy your videos, thank you. Also your guitar playing and also have a Tele .By the By I gave up TV in 1991 .Keep on truck'in
5:49 I was just thinking to myself when i saw the amp flipped "Now that's the penny pinching way of doing it." I just hate to see that too. In a well built amp there's just no need for it and it makes working around the pots a pain in the backside. Just discovered your videos! They are wonderful.
As soon as you add ICs and switching transistors, the complexity increases and so does the troubleshooting effort when things fail. Leo had it right the first time...the KISS rule, and that is why the old vintage Fender amps are in such high demand, and collectable.
my traynor? same: pull the lid= everything right there. can reconfigure 5 ways ta sunday in minutes.jumper clips . too easy. older bassman 10's /eyelet assemblies=easy to swap parts...and fairly forgiving* depending on the order in which parts were installed
the only flaw i see in the mark I (reissue>tubestore) is the presence control. it is not actually a presence per se. since it sits prior to the mstr vol. a prsence control is a "not feeding back" of just hi frequencies from output side of the output tranny. not a tone variance. some use the typical presence to get pinch harmonics more easily when ..? say half way up and use the treb to manage.
Not sure where you live, but if you live in the UK, just book an appointment with the Marshall factory and they will sort it out. They also only charge costs, in fact last time I was there, they didn't charge me. I would never risk any of my amps with anyone but the Marshall Factory...man I love them.
My brain just exploded. I understand everything you're talking about. I have to do similar troubleshooting at work but we don't have to chase it down like this thank god.
Looks almost as if multiple issues were caused by either the owner, or the previous repair dude. First instinct is to usually swap a "known good" tube around in the preamp. Sometimes that "known good" ends up left in the amp, and we all know that "known good" tubes are takeouts for a reason. This kind of work isnt just tech work, it entails a certain degree of "street smarts" as well. hehe It shouldn't be surprising to find multiple issues caused by one person trying to solve another. Anyway, good job. These videos are great. Keep these coming! I watch them whenever I see them.
Any way, I enjoy your videos, I just picked up a Pignose 30 amp cheap and I have replaced the batteries and still won't work , would you care to do a video on that amp ?
Wow man! I am able to completely follow along here now. Incredible! I think it’s almost time for that AO project. I am going to try to add reverb from the ampeg reverberocket ! It’s a 12au7 one tube reverb. Just need to understand how to bias that tube and where to put the reverb circuit in the layout after the preamp
WOW..I did'nt know these type video's were out there...GREAT ... I always wanted to do this for a living...but I can just watch you & the way you explain everything almost makes me think I know what its all about... LOL😎 ..YOU'RE the whip dude... i have a marshal combo...2morro I'll get all #'s & such for you..its not working now..i want you to fix it..how much etc. AND I know that question cant be answered right off😌
Early in the game @ 21:45, I'd suspect a shorted D1 or R3 in V3B. If not that, possible shorted R24 or C18 of V3A. Something's causing V3 to self-destruct, plus there's no signal on the plate of V3B.
I had a 12AX7 tube in a Marshall JMP-1 that did that same popping noise. Replaced the tube and works fine. Thats the only 12AX7 I ever had go bad. It was a very old tube.
Just a short reminder that on July 25th 1983 Metallica released the GREAT album "Kill 'Em All" #JumpInTheFire Also I'm loving the idea of that little girl growing up thinking all of THAT is completely normal. "The first thing you do when you get out of bed in the morning is finish the other half of the tube amp resolder from the night before, then brush your teeth, have breakfast and noodle a few blues riffs before school" etc
The Guitologist It is a JMC 800 Lead Series I have and I like the grill cloth that has been replaced on this one. I don't think mine has ics or transistors. I am debating whether to keep the 6550s or change to EL34s. Most of these 112 Lead Series have EL34s. They are warmer sounding than those hifi sounding 6550s. The overdrive I get from mine comes mostly from the preamp. It is a good pedal amp though. Great video! Lots of comments! Thankz
So what is best guess as to the problem? v1? ...or one of the last 5 or 6 caps? ...dirty socket in v3? ...one or both of the Q's?, ...that resistor @ 'link'? ...v3? ...or, please say it isn't so, some or all of the above?? (plus I'd forgotten all the caps you changed before) Even if there's no definite answer, you had me on the edge of me seat throughout, and it wuz most instructive... so thanx very much, really. And please, keep 'em coming and... cheers
Hey man. I'm in Louisville too. Need to figure out what shop you work at in case I need some stuff done. I've had some bad luck with repairs around here in the past.
I bought this amp. Awesome that I can see the work that was done. The amp sounds great. I put a Classic Lead 80 in it. Also play it through a 1966b with 2 V30s
I had a JCM 900 in the 90s as well. 50w head, not the 100. Had this theory that I could crank up a 50w to get that heavy overdrive sound I wanted without blowing out my neighbors windows. Turns out I was right. Loved that amp and the cannot remember for the life of me why I got rid of it. I recall selling it but I cannot remember to whom or why I felt at the time that I was better off without it for any amount of money.
That 100 K resistor @ 31 minutes provides no feedback, because it would have to be in the 4K or lower range to create enough feedback to do anything, (the gain in that part of the circuit is very low because of the step down transformer, output.) The reason it reads 4.7 K or so is because the output winding is grounded and the other leg of the 100K also goes to the 4.7K (?) resistor a the base of the cathode circuit.. It is easy to test the output by putting a calibrated signal (like 1 volt of 1 KHZ sine into the PI), In most amps that produces several watts of output. Most PI's are really similar
I wish you were my neighbour... I have the 100w head of the same amp 2210. Bought it a month ago fo 300£ because not working properly. Similar microphonic problem but in V1 and pcb which is kind of microphonic as well. I will try to follow the same steps you followed. Change all the elect. Cap including the cans, new pre valves and see what happens.
Damn brother, I love your stuff. But for the love of God, get a sign gen and an o-scopes! They will greatly simplify signal tracing by giving you a visual representation and voltage differential from each stage! An extremely quick way to verify amp stage gain function. Also very cheap to buy.
Hey guys...thanks for the overwhelming response to this one. I've gotten a lot of questions regarding what was the final diagnosis because apparently I wasn't clear enough in editing. The switching transistor TR1 was faulty. Replacing that allowed the Boost Channel to come alive. The phase inverter tube, V5, was causing some sort of issue as well, as was shown in the video, so it was replaced. It tested good on my tube tester prior to troubleshooting. I edit out tube testing from most videos because it gets laboriously long - 50 minutes even without showing tube testing is getting longer already than most attention spans. In fact, you've probably already stopped reading this. The V1 tube tested on the weak side of good on my tester, but I left it in because it should have still worked just ok, which it seemed to do because it is also part of the Boost Channel which was working before I replaced that tube. The V2 tube was the one I finally replaced at the end which allowed the Normal Channel to function properly and fully. The tube I was using in that position during the troubleshooting tested good on my tester, but for whatever reason, this amp didn't like it. The fact that it tested good on my old Precision tube tester is what led me to assume it wasn't the tube and explore other options. Also, if you'll notice on the schematic, the switching is tied into the grid of V2, which is how the Normal Channel gets muted during Boost Channel operation. My theory was that switching in the IC might have also been at fault. Anyway, hope that clears thing up for those of you who had questions. Watching the video back, I can see why it was confusing.
>>you've probably already stopped reading this
The Guitologist I have only just started watching your channel but I have to say you are a star sir! I am an electrical engineer in the UK and have done a little bit of amp repair and build myself, but ultimately I would like to have a set up similar to yours. You bring wonderful old amps back to life that would otherwise be thrown in the skip so well done you hero! 😊👍. Love the guitar playing by the way. Just one question about your signal probe, as you are at plate voltages I presume you have a dropper resistor in line to protect the input of your test amp? Keep up the good work I am already a big fan!!! Keep on rocking 🎸🤘🤘❤️🎸
I believe that every repair comes with a lesson; one of those "I should have tried that!" moments.
If you took away that kind of a lesson from this, what would it be? (Would it be to break out the chopsticks early?)
ha ha ha thats funny brad my bad
Watched and read to the Omega.
The knowledge and focus required to repair such perplexing issues...
RE-SPECT!
I love the way you explained the proces. My kid was watching you like a hawk. This will help many many youngsters. As a DAD I want to thank you.
Awesome! I have over 300 videos like this. Be sure to subscribe.
I did. Thank you.
I'd rather watch an hour long video of you tinkering with an amp than 99% of the garbage they have on TV these days. :)
In a nutshell.
The only thing I watch on TV nowadays is the News, and that is only once in a couple days, fuck the TV
Yep, TV blows. No history on the History Channel. No music on MTV. Propaganda for "news". No learning on The Learning Channel.
Hey! George Stephanopoulos everyone!
agreed. i threw my television in the toilet
I don't understand a lot of what you're doing but I have to watch the whole thing. The suspense, the mystery! Awesome vid.
EYE TROUBLE I USE CAPS :) . I REPAIRED TVS FOR 30 YEARS AND AM RETIRED NOW . I ENJOY WATCHING YOU AND THOUGHT ABOUT KEEPING MY HAND IN REPAIR DOING EXACTLY WHAT YOUR DOING I.E. WORKING ON TUBE AMPS . I AM OLD ENOUGH THAT I WORKED ON TV'S WITH TUBES IN THEM FOR A FEW YEARS AND RETIRED IN 2005 . BUT WATCHING THIS VIDEO SAYS EXACTLY WHY I DONT LOL - I AM ENJOYING MY RETIREMENT . STILL LIKE TO WATCH YOU TROUBLE SHOOT . GOOD JOB. KEITH
These videos are like a murder mystery! Who dunnit? Well, it wasn't Professor Capacitor in the main board with a leak...let's try Colonel Transformer in the mains section with a short...lol
Miss Scarlet Transistor is highly suspicous...as is Col. Mustard Cap's work on the classified fusion bomb.
lol This one was a doozy. It makes you wonder if you should just replace all the tubes in the beginning just to eliminate those as the culprit. I admire your determination and methods of troubleshooting
The highly suspicious find 12AX7A strikes again
Then I would not be able to film myself flailing around like an idiot. :P
But seriously, those transistors were definitely bad also. And it didn't hurt to change all those caps in the switching circuit.
Wait a min... I saw that movie, it was the guitarist from Spinal Tap in the hallway with the Beatles album Revolver! Really, same actor!
THe problem with this channel is it's so addictive. I've lost about 6 hours today. Apart the educational side, I just love your accent and sense of humour (I'm in the UK and just love southern accents) . Please don't ever think of stop making these videos. Just wonderful.
I salute you man! You have an unbelievable degree of patience!
I owned a combo just like this from 1985 to 1987. Best amp I ever owned. A beast. Wish I had it back.
Kudos to you! I recently had my amp go bad and brought it to an amp technician who made it well again. Thank God for folks like you who help make things well when they go bad. Great job!
Had a 2203 back in late 80's. In my case the switching IC was fried. One of my first repairs. Thanks for bringing me back in time Brad!
I'm a completely self taught amp tech and I've had a bunch of those "I'm completely at a loss here" jobs. I spent almost a week off and on with a repair of a simple scratchy pots job in a late 60's Univox stencil amp made by Garnet here in Canada. I initially told the customer it would be a quick fix. Oops. There was constant static throughout the whole signal chain caused by one damn 5 cent resistor.
I thought it was only me who did so much head scratching. Really enjoy your videos and find them very helpful. Thanks Brad!
As an electronics troubleshooter myself (for a living), I absolutely love your videos.
Keep doing what you do :-)
The toddler babbling in the background is fantastic.
She's an absolute nutcase. Takes after her mother. ;)
lolololololololol
I thought she was talking about the amp, what were you saying :-)
She is trying to tell you that British folks never understood electricity. Or maybe it was just the humidity. From cars to amps they showed their prowess.
Live translation for "pre-school school of rock" class.
When all else fails, poke it with a stick.
That has been my motto for more years than I care to admit. Works on women too...so I hear... :P
My High School Electronics Instructor's Motto for working on stubborn equipment was: " If at first, you don't succeed... Use a Bigger Sledgehammer!!"
Sure helps find a valve that's microphonic! lol.
You mean the Coarse Adjustment Hammer and the Fine Adjustment Hammer I assume... I used to have a large mallet on my bench which had "Coarse Adjustment" written on it in magic marker.
Or hammer.
I learned more about circuitry in 2 of your videos than my whole understanding attained in life(44yrs) Thank you beyond words!!!!!
Wow, that was quite a journey. I have one of these amps and after several visits to repair techs I finally gave up on it and bought a new DSL 40. Several years later now, I may open it up again and try a few things, so thanks for the vid!
It's not everyday you see a nice Marshall out in the shade, in nature. Refreshing.
Sounds great dude!!! Love that crunch and midrange!!
That's the Metal Gods tone, man. Gotta love it.
I blew the dust of this vid that I missed back then. Great troubleshooting! I get more confident about tearing into an amp I accidently misinstalled a tube in and it flamed a bit. Thanks Brad, keep 'em coming!!
Damn, I get too into these videos. I was stressed completely out until you figured out the problem like four minutes before the video ended. What drama!
It can really suck when one has multiple issues. You try your best to eliminate variables but it doesn't always work to plan. I did test the tubes before even starting on this, but edited that out for time. Turns out, the 2205 is really picky when it comes to preamp tubes.
Not to be confused as a complaint, I didn't mean for it to sound that way. Great entertainment, that video had lots of drama. Keep'em coming.
I didn't take it that way.
@@TheGuitologistFunny how it's always the last thing you look at.
For having no background in electricity except a little DC theory, you sure have whetted my appetite to learn this circuitry and everything with it. Voicing your train of thought sure makes me feel like I’m learning something. Wish I could go to school and start all over again!
You are like The amp detective... love your videos!
The Amp Whisperer
CSI Kentucky...
I studied electronics in votech (high school)... I passed the classes with a C... I knew then at 17, I would never do this work for a living. I became a Main Propulsion (Steam) Engineer in the Navy... the system drawings were just as complicated but the components are a lot larger, and easier to troubleshoot. 20 years was a life's work. LOL I did follow what you were doing and finding but had no clue as to what was needed. GOOD JOB!
Thanks, Randall. Sounds like the spark may still be there in you.
i like how you go through every troubleshooting step. it really helps for others doing the same.
Hopefully it helps someone. I know the clips seem to skip around a bit in this one. That's because it was filmed over several days and some things had to be edited for time, but it's essentially all there.
19 minutes in, I watched a bunch of this guys videos, I know he will get her fixed up and purring just right and he will shredd up a nice storm on it to test her out. This old cat knows his stuff and plays like a pro, don't none of ya all ever doubt him, he is the amp / guitar master! I love this guy's attention to detail and his incredible perception, he's made so many old ratty things sing like a, well a thing that sings really, Really nice...
Each video is a learning, and proof that the Guitologist, is a great luthier! Congratulations on the great job!
From Rio de Janeiro, Brazil.
I had one of these amps years ago and really didn't like it. It had 6550 output tubes that really are not appropriate for guitar. Marshall made their sound with EL34 outputs. Back about 20 years ago, I saw a Crate Vintage Club amp for sale and I went to the seller's home and demoed it. I was blown away by the tone and, after a short conversation, we agreed to an even exchange. At the time Crate was still make these amps and they had a good reputation. I still have the amp all these years later, but it does require periodic trips to the hospital. At this point the tubes have been replaced multiple time and all of the caps were replaced about 5 years ago. I think my problem with the Marshall was having only one speaker - it sounded much better when connected to a 212 or 412 cabinet. Not to give up on Marshall products, years later I bought a JCM 900 50 watt head and traded for a 412 cabinet. I was very happy with the way that amp sounded. I sold it about 5 years ago when I was moving along with most of my other amps, B-3, etc. I don't know why people trash the JCM 900 - I think they sound good for rock. The JCM 800 and 900 can be traced back to the Plexi, but Marshall stopped manufacturing point-to-point wired amps around 1972, so the DNA is there, but not the mojo. I really don't think tube amps are happy using circuit boards where the tube sockets are mounted on the boards, These amps are difficult to service and sometimes impossible to fix.
I have had the 4212 (50W 2x12 Master Volume) combo from new in 1984. It's never let me down and I only work a few miles from the Marshall factory on the rare occasions when I need a retube or a refurb. The last job was new corners, new handle, new Tolex, new fret cloth, new feet. She looks lovely, but still sports some battle scars.
Alastair Archibald do they cater personally to customers? My jcm900 mk3 was stolen I would like another un abused head.
I have a regular JCM800 combo...Single channel, no reverb. Best amp I've ever owned. Had it for over 20 yrs now. drooped in a Celestion Gold 50 watt speaker.....super nice. Recently had it thoroughly serviced...new caps, tubes, and sockets. Hoping to get another good 20 yrs out it. I think I will too. Solid amp
I know squat about guitars and even less about guitar amplifiers, but you made the process more entertaining & engaging than I would've expected...not least with your brief play-test at close. Thanks for the ride!
This was one of you most informative and entertaining videos. Thank you for including all of it! It is nice to see a repair that didn't come easy but worked in the end. Well earned sir!
Oh Brad, man, I think I may have been feeling your pain watching this repair unfold. I can relate to these difficult examples. Well done with the perseverance dude.
Hey Dan, Good to see ya. Thanks for that. It's funny...it's like some spirit is fucking with you and know exactly where your breaking point is. The moment you get right up to the breaking point, they say "ok, let him fix it now".
Congratulations. Nice job on the trace work.
Dont let it drag you down -awesome video - thanks for your efforts
Original JCM 800 FTW!!! Love those amps!
Dear Guitologist, I discovered yur channel some 6 months ago and really love the way you present and troubleshoot your projects. Having some electronics knowledge myself its very educational and already picked up lot of things I could use for my own modest repairs. Not being able to sent you stuff or make a donation which will significantly change your holiday destignation, which I think you deserve and would like to donate... I choose to express my thanks with..Standing in the Middle of the Street Naked Screaming "LONG LIVE THE GUITOLOGIST"!
Not that I am trying to imply that you suck at what you do I wnder if you are aware of this other repair dude on UA-cam... Mr Carlsons Lab. He is something else.. I always go by the mantra..two always know more than one person. No matter how perfect I think I am, an other person with less knowledge than myself can always contribute something unknown to me. Anyways, thanks for your time entertaining and educating us..
lil bud learning to talk i love it my new fav channel.
The DI is "direct interface" for connection to a mixing console or power amp for larger venues. The 4210 is a great little amp, loud and versatile, killer crunch tone by turning the master all the way up, dial in gain as desired, but will wake up the neighbors.
actually have not watched the vid yet.. the can caps on these Marshalls are extremely high quality and seldom need replacement.
Love the thrash playing at the end once you finally get this thing working! Sweet.
I just got the 5210 out of the shop. Had to disconnect the reverb circuit off the board because of bad design causing noise. It sounds very similar to this. I have an Eminence Texas Heat 4 ohm on the way to upgrade the speaker and I'll be done bringing a 1985 Marshall back to life that somebody on Craigslist sold me claiming "no issues". Haha $300 for the initial Waffle House pick-up from an unknown man in a pickup truck, $200 spent in the shop and $100 on a Texas Heat upgraded speaker. I now own the world's most expensive Marshall 5210. Still less than half of the price in 2021 than the 4210 currently. Priceless.
Using that chopstick reminded me when I was a kid I was given a neon transformer. A guy at my church was an engineer with Muzak and he told me how the make a "JACOBS LADDER" thingies like in those old horror movies. He told me what NOT to do and warned me to be careful. I followed his directions and after adjusting the distance of the wires it was working. He told me if I stuck a wooden dowel or something non conductive between the wires, the spark would stop there. Only wooden round thing I had available was a pencil. I received a quick lesson that graphite can be "conductive".
I had a 82' jcm800 I clipped the clipping diodes out of circuit , made it into a vintage sounding Marshall. Amp builder Doug Bray told me how to do this and it was awesome . good luck
Please make a video on making a signal tracing jig like the one you use. Great job on the channel and awesome videos! I love your sense of humor.
I would like to see this too.
Watching this makes me glad that the JCM 800 I recently picked up is a much simpler design without all that switching crap, and no reverb (1983 4010 vertical input 50:watt 1x12 combo). It is also loaded with a G12M-65, rather than the 70 in the amp in this video. Mine also has 6550’s rather than EL-34’s. I did spend a bit on a full service to fix some issues (replaced tube sockets, new tubes, and replaced any drifted components). Good as new now.
I didn't see you put the negative feedback wire back on, but evidently you did. What a journey
Remarkable ! Wish you lived in the south of France...I quake with fear when I hand my amps to the local dealership/repair dude... Keep up the good work - with all these tips and ideas I'm picking up maybe I'll be able to pass on the dealer and have a go myself...well maybe not...always a pleasure to watch.
Hi, great detective work. I have one question. What were you using to probe for signal in the early part of the video? Where you put a lead on the grid or plate and it would play? By the way No Remorse is one of my favorite songs to jam to.
My probe was connected to the Kustom practice amp in the background there. Nothing special. Poor man's signal tracer.
Yeah, that ending of "No Remorse" was responsible for many a solo mosh pit in my bedroom back in the day! :D
I have had a similar problem trying to get a reading on a negative feedback resistor while in circuit. I couldn't figure out why I was getting such a low value. Then I realized that when the probes were on that resistor, you also have a connection back through the output transformer to ground. In this case, you were basically reading the connection through the 100K resistor in parallel with that 4.7k resistor between the 100k and ground.
Bobby U absolutely right! DC conditions the 100k is in parallel with the 4k7.
Brilliant playing as well as top class repair work. When I did repairs back in the 70's there were very few circuit diagrams available. Keep doing what you're doing, I love it.
So wait... would a new set of tubes have fixed the problems from the start?
i dont think so because a transistor was faulty, etc.
Sounds like you need a tube tester to screen these things when they first come in. Would've eliminated a weak tube at the start.
I have one and did test the tubes. DIdn't include those video clips in the final edit because of length, but the tubes tested fine on the tester. V1 was a bit weak, but still should have worked. Probably would work in anything but this amp. This model seems to be really picky about tubes.
I have a 4210 on the bench which I had to replace the power switch (melted), replace PT, do a rectifier diode work around because the board was burnt up and all traces gone. Someone did work their which caused the rest of the damage. Amp up working but if you turn the reverb pot it blasts into oscillation. The work continues. Mark
I too had a 1x12 50w JCM 800 combo from '86. Bought it used for $250 back in 1995. Almost from the get-go, this thing had issues: From bad tubes that were rattling, the clean channel breaking up too much too soon (when I wanted the damn thing clean), and the speaker being mounted in a weird place (just lower right of center). Even after getting it re-tubed and serviced twice, the issues were still not resolved. But the REAL FUN occurred when I tried to take it out on gigs. I could never EVER hear it, even with the master volume cranked up. Got bitched at by the band leader for being too loud. So I tried to face it toward the wall. Couldn't hear anything at all, and then I got bitched at for playing sloppily (b/c I couldn't hear myself). Long story short, that amp actually COST me gigs rather than helped me get 'em. Ended up selling it for DOUBLE what I paid for it (hence, what the interested party OFFERED to give me for it), and was only too glad to let it go! I said NEVER AGAIN to getting another JCM 800 after that!
Nice job man, that took alot of patience and knowledge!
I have always played around with radio and amps. Not so much nowadays. I have been a Bass player since 1965. I enjoy your videos, thank you. Also your guitar playing and also have a Tele .By the By I gave up TV in 1991 .Keep on truck'in
my babbling little girl turns 1 this week. we've been watching these repair videos together in COVID quarantine
I used to have the vertical input 2x12 50w combo. man that thing was a beast and heavy.
Great vid Brad,you go at those amps like a well focussed laser.Love looking at and hearing the Junior too.I am jealous.Thanks again man.
Great video! What do you use as a singal trace device?
5:49 I was just thinking to myself when i saw the amp flipped "Now that's the penny pinching way of doing it." I just hate to see that too. In a well built amp there's just no need for it and it makes working around the pots a pain in the backside. Just discovered your videos! They are wonderful.
As soon as you add ICs and switching transistors, the complexity increases and so does
the troubleshooting effort when things fail. Leo had it right the first time...the KISS rule,
and that is why the old vintage Fender amps are in such high demand, and collectable.
You are so right. Way too many engineers out there trying to re-invent the wheel.
I had an old Mesa Boogie Mark 1, no complicated electronics on this, hand soldered
For Marshall the 1959Plexi heads are the one's to hold on to
my traynor? same: pull the lid= everything right there. can reconfigure 5 ways ta sunday in minutes.jumper clips . too easy. older bassman 10's /eyelet assemblies=easy to swap parts...and fairly forgiving* depending on the order in which parts were installed
the only flaw i see in the mark I (reissue>tubestore) is the presence control. it is not actually a presence per se. since it sits prior to the mstr vol. a prsence control is a "not feeding back" of just hi frequencies from output side of the output tranny. not a tone variance. some use the typical presence to get pinch harmonics more easily when ..? say half way up and use the treb to manage.
came here to watch the luddites, am not disappointed
Not sure where you live, but if you live in the UK, just book an appointment with the Marshall factory and they will sort it out. They also only charge costs, in fact last time I was there, they didn't charge me. I would never risk any of my amps with anyone but the Marshall Factory...man I love them.
This is like watching a horror movie. Keep waiting for something to go ZAP! I rather leave this for your pros :)
My brain just exploded. I understand everything you're talking about. I have to do similar troubleshooting at work but we don't have to chase it down like this thank god.
Nice playing there at the end my friend!!
Looks almost as if multiple issues were caused by either the owner, or the previous repair dude. First instinct is to usually swap a "known good" tube around in the preamp. Sometimes that "known good" ends up left in the amp, and we all know that "known good" tubes are takeouts for a reason. This kind of work isnt just tech work, it entails a certain degree of "street smarts" as well. hehe
It shouldn't be surprising to find multiple issues caused by one person trying to solve another.
Anyway, good job. These videos are great. Keep these coming! I watch them whenever I see them.
always start with the tap and wiggle tests! lol. these are very amusing for me coming from electrical diagnosis failure
Any way, I enjoy your videos, I just picked up a Pignose 30 amp cheap and I have replaced the batteries and still won't work , would you care to do a video on that amp ?
Wow man! I am able to completely follow along here now. Incredible! I think it’s almost time for that AO project. I am going to try to add reverb from the ampeg reverberocket ! It’s a 12au7 one tube reverb. Just need to understand how to bias that tube and where to put the reverb circuit in the layout after the preamp
Dude your videos are incredibly informative to someone like me. Appreciate everything you do and how in depth you are!
Don't lie, you just want to see me go ape and smash stuff. :P
But seriously, thanks for saying that. Much appreciated.
kylendm I
Sweet git at the end. Awesome sounding jr.
WOW..I did'nt know these type video's were out there...GREAT ... I always wanted to do this for a living...but I can just watch you & the way you explain everything almost makes me think I know what its all about... LOL😎
..YOU'RE the whip dude...
i have a marshal combo...2morro I'll get all #'s & such for you..its not working now..i want you to fix it..how much etc. AND I know that question cant be answered right off😌
Early in the game @ 21:45, I'd suspect a shorted D1 or R3 in V3B. If not that, possible shorted R24 or C18 of V3A. Something's causing V3 to self-destruct, plus there's no signal on the plate of V3B.
I am at 16:36. I had an old executive or electrovoice pa that had barely no output. It was a burnt resistor. Now, back to watching.
Your problem was a heater cathode leak on one of the valves TR1 only switches the LED on and off. It is getting it's supply from the heater 6.3V
I had a 12AX7 tube in a Marshall JMP-1 that did that same popping noise. Replaced the tube and works fine. Thats the only 12AX7 I ever had go bad. It was a very old tube.
Marshalls are hard on 12ax7 tubes.
Just a short reminder that on July 25th 1983 Metallica released the GREAT album "Kill 'Em All" #JumpInTheFire
Also I'm loving the idea of that little girl growing up thinking all of THAT is completely normal. "The first thing you do when you get out of bed in the morning is finish the other half of the tube amp resolder from the night before, then brush your teeth, have breakfast and noodle a few blues riffs before school" etc
The baby looks like her Dad! I have a non-reverb single channel with 6550s and this will probably help when I rehab mine. Thankz
The milkman is not that good-looking. :P
You shouldn't have any of the switching issues with yours.
The Guitologist It is a JMC 800 Lead Series I have and I like the grill cloth that has been replaced on this one. I don't think mine has ics or transistors. I am debating whether to keep the 6550s or change to EL34s. Most of these 112 Lead Series have EL34s. They are warmer sounding than those hifi sounding 6550s. The overdrive I get from mine comes mostly from the preamp. It is a good pedal amp though. Great video! Lots of comments! Thankz
Cool little amp! Hello from across the river a bit, in Corydon, IN.
Hi neighbor!
I love learning about amps... I have Valvestate 80 by Marshall. I love it.
Nice video. That guitar and amp sound great. Nice playing at the end.
So what is best guess as to the problem? v1? ...or one of the last 5 or 6 caps? ...dirty socket in v3?
...one or both of the Q's?, ...that resistor @ 'link'? ...v3? ...or, please say it isn't so, some or all of the above?? (plus I'd forgotten all the caps you changed before) Even if there's no definite answer, you had me on the edge of me seat throughout, and it wuz most instructive... so thanx very much, really.
And please, keep 'em coming and...
cheers
Hey, a new subscriber here; thanks for taking all the time to video, edit and upload this info...I REALLY enjoy your videos!
After all the investigating and the feeling of accomplishment .. i always love the 'pay-off jam' at the end ...
Pretty sure when you asked your kid to say Marshall, the reply was "I want an AxeFX". Oh no!
hahaha....no!
I heard at 4:59 "Kemper profiler"...
be glad you didn't forget to plug it in! that would have taken WEEKS to diagnose!
Hey man. I'm in Louisville too. Need to figure out what shop you work at in case I need some stuff done. I've had some bad luck with repairs around here in the past.
bradlinzy at gmail
magic amp pixies de-mystified! thanks for the detailed trouble shooting.
Thanks for watching!
I bought this amp. Awesome that I can see the work that was done. The amp sounds great. I put a Classic Lead 80 in it. Also play it through a 1966b with 2 V30s
Great video, as always. Thanks
I never had an 800 but loved my JCM 900 when I owned it back in the 90s.
I had a JCM 900 in the 90s as well. 50w head, not the 100. Had this theory that I could crank up a 50w to get that heavy overdrive sound I wanted without blowing out my neighbors windows. Turns out I was right. Loved that amp and the cannot remember for the life of me why I got rid of it. I recall selling it but I cannot remember to whom or why I felt at the time that I was better off without it for any amount of money.
Great video, explaining, and playing.
As an observation,how about a scope ,an audio generator and a dummy load for fault finding,might be easier,regards Colin.
Retube with a pair of Groove Tubes EL34M and for the preamp V1 NOS Mullard ECC83 short plate , V2 NOS RFT ECC83, V3 NOS Telefunken ECC83.
I always wanted an 800 . Its connection to the New wave of British heavy metal is synonomous .
That 100 K resistor @ 31 minutes provides no feedback, because it would have to be in the 4K or lower range to create enough feedback to do anything, (the gain in that part of the circuit is very low because of the step down transformer, output.) The reason it reads 4.7 K or so is because the output winding is grounded and the other leg of the 100K also goes to the 4.7K (?) resistor a the base of the cathode circuit.. It is easy to test the output by putting a calibrated signal (like 1 volt of 1 KHZ sine into the PI), In most amps that produces several watts of output. Most PI's are really similar
I have a Marshall 5210, which is just the solid state version of this. I rebranded it as a JCM-800 hehe, gold plate and all.
I wish you were my neighbour... I have the 100w head of the same amp 2210. Bought it a month ago fo 300£ because not working properly. Similar microphonic problem but in V1 and pcb which is kind of microphonic as well. I will try to follow the same steps you followed. Change all the elect. Cap including the cans, new pre valves and see what happens.
Good luck! Keep us posted on how it goes.
Damn brother, I love your stuff. But for the love of God, get a sign gen and an o-scopes! They will greatly simplify signal tracing by giving you a visual representation and voltage differential from each stage! An extremely quick way to verify amp stage gain function. Also very cheap to buy.