I bought a JCM 2000 used and after a week or so it developed a similar problem. Sent it in for repair and it came back sounding great. That was 5 years ago and it's still going strong with no problems. Love that amp.

This is so weird- my jcm2000 DSL100 is following the same exact issues in the same order as this one. You're saving me a yit load of troubleshooting time. Thanks!

I owe you some dough because I had to put in a new JCM2-60-00 Revision 20 board in and you helped me with that. Thanks to you, I also bias'd it. It was WAY off. If you have a paypal or another method, I'll send you $50 because you saved me at least $200 so far. Thanks and I hope you all are staying safe. Great videos.

Brad the beauty of your channel is that I watch EVERY video for no real reason

Working on this same amp (combo) and thanks so much for explaining the tube swap voltage test. Just tested it and the values carried over when I swapped the tubes. Screen recorded this to have it in my back pocket. You’re the best Brad!!!!!

I have a JCM2000 DSL 100w from 1997. Mine was one of the first ones off the production line because it was an artist endorsed amp. The amp ran about an hour before the tubes started melting down. The problem (amongst many) was the bias drift. All the boards were changed and several components were upgraded. What a major pain in the ass. But in terms of sound, it s the best Marshall I've ever had. It's been in service for well over 20 years and since the boards were changed out, I've never had a problem with it.

One of the best most detailed troubleshooting videos I've seen. I'm about to look at my friends JCM2000 DSL100 tomorrow and wanted to get some reviews of some of the common problems with them and he says his keeps blowing fuses too, so this video certainly gave me some ideas on things to look for. Thank You for taking the time. Nice Job!

The first repair I ever made on an amp was my JCM 2000 401 that would intermittently loose power to the tube heaters. I was nervous messing with it but luckily it was a common problem with the bridge rectifier. I later sold that thing and people like you have inspired me to use more vintage style amplifiers and I couldn't be happier with the tone and serviceability.

Man, thank you so much for these videos. I have learned an amazing amount from watching you.

Love these videos, I don't even own a marshall I just like seeing things being traced and fixed, we're all nerds I guess, keep up the good videos! Now everybody with a 2005 with same symptoms can learn what's going on with it, :D

Hi Brad, one of the best variable tube amps from the big Jim M! Good job done!

Man I just can't get over how valuable these videos are. I have an MTS Carvin... Well gave it to my old girlfriend and thus don't have any tube amps anymore but these videos are my type of TV. Always learn something. Every time.

This is enlightening...my 30th anniversary amp is playing up again (120mA on each side and climbing) and humming as well. Watching this has switched on a wee light at the end of the tunnel. Thanks for that mate! Btw, I'm sure that you snuck in a wee slayer riff there...spot on! :)

I like your style. You are very through and explain carefully everything you do. Great Videos and super channel. Hats off to you, man... Thanks

I have a 2002 Marshall JCM 2000 DSL 100. It had the bias drift problem. A few minutes with a Dremel and four new grid resistors for the power tubes and the problem is solved. Bias is rock solid. Touched up the solder joints on the bias adjust board while I was in there since that's a common failure mode (cracked solder joints). The amp plays great now and runs very stable. These amps get a deservedly bad rap for poor engineering of the main board but it's an easy fix and you end up with a great amp that rocks.

I wish I knew what you know, but that would take school and a huge amount of reading and work on amps. Really great job :)

lol, how did I miss this contest .... sounds fun. Enjoyed this vid.. Thanks.

Kudos to you sir. You know your stuff! I blew my amp the other night. Same one you have here (JCM2000 DSL 100 watt into a 1960 dsl900 4x12 cab). I was playing on "2" for about an hour when my other guitarist decided to crank it at practice. I got tired of him blowing us all out, so I turned the amp up on 10. Struck one chord and... crickets. Used my backup fender amp to finish practice. Now looking further into my prob, I see that an EL34 has blown. Looking from the back of the amp, it is the left outermost tube. I also blew the D198 250 VA fuse. No smell in the amp so I hope I didn't blow anything else. Didn't make note when I unplugged everything (it was late) but I believe I mistakenly had the cab plugged into the 8 ohm output on the amp. :( It played for an hour, so, I'm not sure if the ohm mismatch blew it or not. But if it did, where else would I have issues? Also, where can I get another D198 fuse? Thanks so much for any help you can give!

It's cool you didn't have to change the entire board like some people recommend. It looks like Marshall got a hold of some bad capacitors. The 2000 series amps sound really good when they're working properly. I have two Marshall TSL60s . Once I accidentally hooked my 4x12 into the TSL's effects loop and blew a fuse when I powered it up. After that I put yellow electrical tape over the effects loop inputs to make sure I'd never do that again. Good video!

I serviced a DSL100 that had this exact same problem, Santiago really brought Marshall into a new era with his excellent and non-problematic designs. I guess it will be back to the old Marshall bombs now that he's gone.

I had the same problem with my 50watt head. Unfortunately my tech said it was all too hard, the mother board was stuffed and I had to say goodbye to it. So sad , it had been my favourite for a few years! Wish you were my tech...cheers from Downunder......

Excellent vid, liked the diagnostics, following the problem was an excellent instructional, could be used on any marshall, I was surprised to see that cap on the power switch input circuit was bad, something to remember, Great vids, thanks a lot, use them for my own repairs, however limited. Also another really great fact about the different issue numbers on schematics and amps! Thanks again!

Love your channel, content & etc! Played music all my life! Had 2 piece together my 1st radio/Bobby Bushea (or however it's spelled) grew up in my crazy, strict, religious, Aunt's house from age 6-11/ no radio or television! Was given a beat & busted/ repaired acoustic at the age of 8 or 9 & found a radio board missing a lot & pieced it together, added a new power invertor, touched head phone leads to where I assumed an output was until I found it & had to hide it when not in use!!! At the age of 11, I was FREE AT LAST!!! Been playing guitar ever since though, a disruption in 2013 & junk from then till now with the exception of one acoustic that I bought at Moore's Music emporium but, Needed money & away it went! Heartbreaking!!! Love your content!!!

Another chart topper! Thanks so very much fer chasin' my Blues away and helping my brain keep on Keepin' on!.... cheers

Happened to mine after 17 years. Died right in the middle of a show. Really happy I had a good tech in the area.

I'm glad I did my research and found this upload because I was about to buy a JCM2000 DSL. HELL NO! Wow what a 'bucket'.

I've got the same Vizio TV remote that is shown later in the video. Great vid..

Great video, I don't repair amps but I enjoy watching you do it :). Must be the sadist in me lol.

I've only built stomp boxes from kits, carefully following the directions. I have no idea what you're doing in these repair videos.....and yet.....I've subscribed to your channel and watch every minute of them. I can't get enough. I think I may have some sort of compulsion disorder.

I had another one of these to check over couple of weeks ago and one of the screen resistors had fell completely out and was rattling around in the box !! Hahaha great soldering they did....

Excellent job. I have been a 100% Marshall tube amp guy going back to 1979. I don't play anything else. My current long time babies are a 1991 JCM 900 Model 2100 which I had repaired a few years back by Gary Lowe (Randy Rhoads amp/electronic tech) and a Vintage/Modern Model 2466... if you work on either of these, I am all eyes and ears.

I have been watching you for a few years now and you've not only inspired me, I get allot from you're electronics knowledge and guitar playing, I play and I do work on electronics as well. Back in the 80s i worked on VCRs and stereos etc, I played music as well.(in church). During those years electronics was only a side job and I had to stick with working with my dad in house exteriors...... not quite my interest but I had to make a living..I started a small recording studio and I did pretty well with that but that was before things went digital and folks could buy software for their computers lol... Long story short I recently got back into playing and singing and working on radios and amplifiers... pretty much had to repurchase equipment over the past few years, lol Thanks so much for your videos Brad. keep em coming when you can..... prayers and blessings, love and peace, safety and prosperity for you my friend God bless!!

Good detective work on this one. I have to admit Brad that I did not know Marshalls had the bias test points like the ones you were using. Very cool. Too bad to see bad solder joints like the ones we saw here.

Brad, I was trained by the Navy as an avionics tech, back in 1970, and used to enjoy tinkering with tube amps (as a bass player since 1967). This video, however, has convinced me beyond all doubt that I never want to see the insides of one of these newer monsters!! God bless your patience, persistence, and curiosity! LOL You're a better man than I, McGee! LOL Is your piece of trash a fuse?

I got that component tester in a small box of components I got from Amazon, the thing is great like you say. I use it for going through my old computer parts and seeing if they spec out for use in guitar stuff. Lots of great caps and such, even some CMOS chips make for great synthesizer parts.

Awesome tutorial thank you so much I learned alot. Thank you for sharing your talents greatly appreciated

Had a bias runaway with a 2000 series last year and after a good deal of research on the internet, the only way I solved the problem was to remove all 4 PA valve bases and dril 6mm hole where each grid pin came through the PCB, refitted the valve bases and wired the grid stoppers directly to the grid pin. What's happening is the PCB coating is conductive (Marshall know this!). this stopped the bias runner way. ALSO some of the random noise from the speaker was due to the track thickness on the heater circuit not suffient to carry the large heater current. I therefore rewire the heater to all valves with good quality heavy cable which cured the noise problem. My advice to engineers who get these amps in for repair is - run for the hills!

I owned a TSL 60 head and the clean channel on that thing was awesome, as was the reverb. Miss that amp, never had an issue with it and I think I owned mine for 15 years or so before I sold.

Colored zip ties, and matching paint = Seriously helpful when you have to pull unmarked harnesses that can be plugged in anywhere.

I still can't find out why i find your videos so fascinating. But I know one thing, if I lived near you, I would not let no other than you touch my amp. Good craftmanship and meticulous approach. Like it.

Rocking thingie from the insides of a 3pdt switch!!!!! You changed one in a pedal recently!

Man I enjoyed that, thanks for posting it

Screw the DSL. Mine fried a tube that took out some resistors and a tube socket with it. But I did enjoy your troubleshooting. Mine was screwed up as bad as this one. I love working on my hand built plexi clone compared to the DSL or HVM.

Great video bro and good you tracked down to problem. ATB

Brad, I have fixed the Thermal Runaway issue with these amps. The circuit board material becomes conductive over time and then the tubes loose bias and then runaway. I isolate pin 3 of all the power tubes from the board by cleaning around the pin with a dremel. Then a jumper wire is installed to complete the circuit that you have cut.

I don’t know anything about electronics. But this is a great video about repairing a jcm2000 .

I love R8's & R'9's myself but I only own a Standard, oops wrong video. Just kidding, thanks for sharing your knowledge Brad great video as always. I have a 1988 fender "the twin" and it needs some work on it bad. Crackles and pops all day. Probably needs all new caps and tubes.

My perfect slow TV… thanks man!

90mv is 45ma per tube - hot! Those pots are highly interactive. I was thinking that they adjust the tubes on the opposite side. C46 has a tendency to blow short. You are lucky that you didn't have the dreaded conductive PCB issue, which requires some work with a Dremel. Thanks for the tip on those caps.

He might act like the Queen of England but he's really a British spy. Brad, the Marshall whisperer.

I had one of these. Same problem and it ended up burning the board. Something to do with the PCB design and traces of the earlier ones. Amp tech bypassed those traces by hand wiring that part of the circuit. He called it 'lifting'.

Nice video !

Love your vids... to think my first amp for Bass was a Linear Concord HiFi Amp all Valve back in 1962...then Selmer Treble n Bass 50watt heads & Selmer Goliath/David Cabs 3x Heads with 3x18 Cabs - proper music gear.... now about my 100watt Seymour Duncan 'Convertible' Amp - got it back in 1988-9 hardly ever been turned on and only in Studio setting... Guitar & Bass eh! tricky decisions. Thanks for Posting truly amazing and love the guitar playing. Michael @OAK77uk Tweetland/FB

Just bought a jcm 2000 dsl and all 4 of my tubes are red plating. Got a great deal on the head and a Mesa 4x12(head was more or less free if you look at what the mesa cab sells for)going to take it to a reputable tech in the area. Hopefully it doesn't cost an arm and a leg to fix

Strippers on a pole.. Love it!

Mate ! , I was waiting for you to find an intermittent short on/in, a power tube .. I shelled out for a tube tester to eliminate faulty tube dramas at 1st base.. I read up on tube control Bias a lot lately , and i find the current sensing resistor , is there not only to reference milliamps to millivolts , but it is also to protect the control grid like a fuse would .. which is why you only should use just a half watt , 1 ohm type . (of course if you use 10 ohm , it would show 10 mV for 1 mA). When i build a fixed bias amp, i make sure i have available, as a bias voltage , at least 10 % of the plate voltage , at the middle of the bias pot travel . so if the amp idling( all volumes and eq turned down to 0), has a plate voltage of say 480 dc volt ,, i want -48 v on the centre of the bias pots travel .and i want to be able to adjust that by 25% each way at least . There could be a problem in your bias voltage supply .. crap filter cap , resistor ,, and make sure you have a decent negative voltage on the control grid . Pin 5 on that octal tube.. Over here in Australia , the amp companies built large amps with insufficient bias control , and the same with heater current . i had an amp built here that had 6 of EL 34 and 3 of 12 ax7's , and the heater winding for the power tubes was only good for 6 amps, which is why it chewed through tubes , stripped the damn cathodes ! when the fault takes out the current sensing resistor , its preety much saving the output transformer from dying ! Cheers Brad ,, love your work ..

Lools like board hell on there. Same as my JCM900. Nice clean channel, lead is a dog. Need a "Z".

I got lucky with my TSL 60 heads I owned for about ten years, about 6months after i sold them they started to have problems and this was one of them.

That was a good vid, awesome!

Brad, Great video as always! Double check me on this, but I think the 8 & 4 ohm jacks get their ground from the make/break ground contacts on the 16ohm jack. I believe you see where I’m going with this and the possibility’s for bad things to happen. Jumper the grounds on the 16 ohm jack, from one side of the jack to the other. If your test speaker was plugged in the 8ohm jack when the HT fuse blew................

16:03 I just bought one of these off reverb and that's the noise it made as soon as I turned it on for the first time. I'm in the process of sending it back, lol

A good idea for a video would be converting a tube amp to solid state or vice versa. Another good idea would be a video showing how to convert one of those line 6spider valves into a normal non digital tube amp by bypassing all that digital crap. Love the channel.

Excellent!

Man i had a TSL 100 that would run away. Id send it to my guy hed bias it then give it back and it would do it again. After about 3 sets of tubes i did some checking and found bias resistors that woukd thermal reactive. They would change value with a hair dryer on them. Finally got a new main board and the problem went away. Funny thing all thise suspucious resistors were changed to better ones. I hate engineer bean counters. Now i play a metro and a matchless. No more pcb for me. Keep on keepin on.

All right that does it! I’m gonna shipping my mesa boogie rectifier head! Lol. I don’t believe my local tech who is supposedly certified through Mesa does a thorough enough job. Of course after seeing your Roadster troubleshoot.

Knows His Stuff Indeed👍

Thanks for this video Brad, this was really interesting. Blew my mind when that particular cap measured so bad. Lots of plugs and wires to disconnect and mislabeled schematics from the factory, that’s kind of an automatic handicap right? This was cool 😎 as usual, you rock.

What I experimented for years it's in many cases, sound or bias issues rarely come from the tubes. Nowadays tubes don't fail that much often. Usually tube amp issues come from: bad solder joints, capacitors, diodes or even resistors.

Well, perhaps the most important lesson I learned here is....I don't want one of these amps...ever, lol. But great video. Thanks for posting!

Love the channel Brad, I'm a first year Electrical Engineering student in Canada, and you really inspire me. How would you go about learning more about tubes and amplifier circuits? We dont cover Tubes or anything like that in any of my classes and this is the industry I want to work in. Thanks again, Anthony

Exact same thing happened in my TSL, same resistor exploded and took out the smaller 1/4 watt below it. I had just installed a quartet of JJ 6CA7 tubes and "it go boom" too. Replaced the 1 ohm resistors with flame proofs. My board is the darker green version although not the latest issue. The amp is from 2006. I put the original stock Svetlanas' back in and no fireworks. I'm going to check the cap you replaced on mine. Another poster said these Marshalls' don't like JJ tubes. Looks like there's a trend.

I'm sure it's REAL helpful one year out but it may actually be one of those JJ tubes, I have a Fender amp that had 6 6l6s in it and one actually internally shorted and blew every (going on memory of what my tech told me) resistor(the 470 one) on the bias on that side, took out the B+ line, melted the wire on the heater string, and literally melted the tube socket from how bad the arc was. He literally had to rewire the output side of the amp. If it had been a PCB it would have basically been trash. This is not the first time I'd had an issue with JJ output tubes, I had one redplate new out of the box with bias that was absolutely perfect in a Pignose. Both of these amps were working just fine when they failed, with different tubes(biased according to JJs), and I'm extremely lucky it didn't completely kill the transformers on the Fender. Wish I had a video of when it happened, damn tube must have lit up like a light bulb.

Applause, applause! Way to chase it down!

Sidewalk item: rocker plate from a toggle switch ✌️

Hi, great channel, loving the videos, man. I’ve currently got a TSL100 on the bench, she’s blowing main fuses- it's a revision 6 main board. I’ll most likely will replace it with the newer revision 20 board, but want to do some more tests first before I have to give the owner the bad news... I’m currently checking the power supply board - exact same one as one your DSL100 (issue 3). Coincidentally, I had very similar readings as you got when testing the two caps… C16 measured fine at 22uF, but C2 measured only around 20pF !! These caps are labelled the same so both should be 22uF. I just found that a little odd, exact same symptom, exact same cap. So i'm wondering if anyone else has had this happen and if in retrospect anyone can shed some light on why. I’m wondering if the reason is further down the line somewhere, rather than an isolated case of a bad cap.

Last night, couldn't sleep, couldn't play guitar because it was too late and the British police are on your case if you're being too loud but won't do a thing if you complain about noisey neighbours yourself... I guess they don't like Psychedelic Stoner Doom being played through a 6x12 rig... So, solution: I had a Guitologist marathon with plenty of home made ice cream. I particularly enjoyed the Train Club one. Great stuff! :D

I watched your video. You had a spark inside the 3rd output tube from the left. Bad tube. There were many clues to this end. First was the blown resistor. Only way that resistor would explode the way it did was with a ton of current very fast.

Sup, as I remember, 1998 to 2002 for the dsl 50 and 100 models were infected with the conductive boards. Heated overtime to conduct. I think I understand it. good luck.

For those asking, here is the link to the exact component tester I used in the video: goo.gl/FzQi7Z

On these amps I always have to replace the caps in the bias circuit and if I cannot dial up to 90mv per side then change out the bias range resistor. Tube matching range also is a problem so your mA readings vary with what pair of tubes your running. Mark

I would have never guessed to be looking at Capacitor C2 since it was bad on the high tension circuit.

Excellent troubleshooting work!

I haven't used a Tube Amp of any really all that much since 2009..thats when I tried the Marshall MG 100FX 2X12.. no need for Tube Amps anymore to achieve the warm to hard driven tones and everything in between the Solid State Amp technology the past 20 years is simply incredible this is why more and more guitarist are turning to Solid State Amps today plus their also much more reliable than Tube Amps..in the 9 years I have had my Marshall MG 100FX and my Line6 Spider IV 75 Watt Amp 8 years not one single issue with either one of them ..I can not say that about a bout my Tube Amps..

great vidio

I've bought one from a customer for £50 , as the solution to the runaway bias from the conductive pcb is a new board from Marshall , £125 , I think was the price . Plus labour , not cost effective for him . But eventually I'll modify the old board with the "Dr Tube" drill and mod method . I think I paid £60 for the kit .

I noticed that flash and also was waiting for the intermittent short test of the output/power tube/s. I also noticed these Marshall's have gone the way that Blackstar Amps have gone, with the tube/valve sockets mounted directly on the PCBoard. If I live long enough, we shall see how this works out for the amp companies.

Man, am I glad I bought a Bugera Infinium head instead of a Marshall!

How many times did you say mother F er when you were working on it? This should have been called the nightmare of all Marshall amp repair videos. You have much more patience than I do. :-)

My TSL 100 seems to only blow the 1 amp fuze on bigger stages with lighting etc. i plugged it in and it blows before even turning on standby. All the lights on amp are on but no sound? Will a good surge suppressor help?

I like your videos very informative.brad I got a question I own a fender blues deluxe reissue,i retube it with a different brand tubes and my bias range between 15ohms to 62ohms,it is safe (not to stress)to bias between 32 to 35

One thing you didn't mention though you kind of demonstrated it when you were adjusting the bias. The bias on these amps is push/pull meaning you have to adjust each side to the point where both are as close to even as possible but to do that, you have to go back and forth as raising one, lowers the other, etc.

Sorry Brad, I think you missed this one and this amp will be coming back. A power supply cap can't burn out the cathode resistor or cause that tube flash. Assuming that tube still works, I think that tube is shorting. That's about the only thing I can think of that would cause that flash. If the tube is now dead, then there was excess current though the tube and it burned out a wire inside. But if loss of bias can't do that, then it suggests a internal short. It happens. That why tube checkers have tests for shorts.

Hi Brad. I was just wondering how it was that you were able to determine the primary current as you were using the Variac? Does your variac have a digital display that is able to read the primary current from the DUT?

The thing on the sidewalk is an excessive vibration indicator used in packing of delicate products. If it is broken, then it shows the package was handled roughly during shipment

Rocker switch plate from one of your stomp box videos.

I saw the Pawed Gretch give back and i cant find tat video ? Alougth , it broke my heart that guy iz a REAL DEAL MUSICIAN ! A real musician helpz other musicians ...If they can It reminds me of the. SG i lost that i bought the nite before i lost .my. Wife ...some of her last wordz to me were I luv tat guitar! And so i to all the plastic bell, pickgaurd, and rear electronic plates and those were chromed also...i kno dont hav. Any thing to do wit tiz vid, but I wanted to tell ya my story I am a poor man by all mean z ...but maybe Some day i will get another 2015 cherry sg or other year and memorialize it for her.. I luv ya repair vidz they ARE my fav videoZ ON here im not bad tech but watching you teachs me tingz i didnt kno as good az i do now im 1 of ya biggest fan z .....But the Guy ya showed reuniting him wit his Gretch guitar brought a tear. ....To my eye.. Thx for all ya taught me regards Shaun

I had a TSL JCM 2000 and it had this issue. Had to get a replacement board from Marshall. It has had about 16 reissues and was a big problem that Marshall had a hard time even figuring out. After the one board was swapped out it was fine. But holy shit what a nightmare. I eventually sold it

God forbid they name them like Con5a to Con5b. Have that same Fluke DMM, love it! Cheap tools are great for a lot of stuff, but the DMM is not worth skimping.

Never seen the inside of a tube spark... Crazy

I love how exploded that resistor was haha