Mother of All Marshall Amp Repair Videos - DSL100 Blowing Fuses, Bias Runaway, Fun Times! 

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!

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

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.

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

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

I 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.

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.

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!

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 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......

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!

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!

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'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.

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 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 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!!

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.

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.

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

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

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 ..

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

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!

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

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

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 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....

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.

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.

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

Hmmmm! Is this head worth buying to begin with, or should we sit back, buy them used, and fix them so they live?

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'.

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................

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.

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

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.

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 :)

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.

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!!!

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

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

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.

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.

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'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'.

Hey Guitologist, just a suggestion: purchase a label printer that can print on shrink tube- I did my JCM2000 and it makes connecting everything back up A LOT faster and more accurate. It's worth the investment.

I have a 2004 DSL100. Should I be worried? It also has JJ Tubes 😮

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.

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 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.

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.

Sidewalk item: rocker plate from a toggle switch ✌️

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

Did you check to see if that cap was dc-shorted? Just curious, thanks for taking us along for this!

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.

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

Hi Brad, really like your videos. Just watched this one about the Marshall amp. I think you'll find that one pair of the output tubes has an intermittent short, causing the HT fuse to pop. Nothing in the HT feed would cause those cathode resistors to burn. I have worked on high power vacuum tube amps for many years, and have found output tube flashover to be the #I reason for HT fuses blowing. Of course, loss of bias can also cause HT fuses to pop, but normally, in the case of loss of bias, the fuse will blow again nearly immediately. I'd also check the grid coupling capacitors for all the output tubes. A short there will cause an output tube to draw enormous current as you know. Keep the great videos coming.

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

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.

Another idea. Why did the tube spark? Could there have been a nasty quick burst of parasitic rf happening? I have been known to add screen resistors in amps where they were absent and increase their value slightly in amps already with them. Also any screen or grid-block resistors must be as close to the tubes as possible - preferably right on the socket. And I never use anything less than a 1-watt power rating cuz the little guys are too fragile. Besides we are dealing with high voltage, and bigger resistors resist high voltage spikes better than small ones. In my lab where I operated and maintained a 2.5 mega volt van de Graff we were always concerned with resistor spike voltage ratings too, besides their wattage.

Strippers on a pole.. Love it!

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.

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

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

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!

I have a 1998 model and a 2005 model of this dsl100 amp.Back in around 2000,I bought the 1998 from the now defunct mars music.I had it for a couple of weeks,and it started blowing the HT fuse.So I replaced all the tubes.It didnt fix the problem.I then took it to a marshall service center which was less than a mile from where I lived.They kept it for about 3 months,and finally called me to come pick it up.That they couldnt figure out what was wrong with it.They only charged me about $40 to work on it.Even though it was still under warranty.I asked them what they thought the problem might be?He said he thought maybe it was the power transformer.So I decided to try and troubleshoot it myself.I have an electronics background,and have worked on tube circuits before back in the 70's.I must have spent over a hundred hours or more working on it.And I never got anywhere.My problem was the drifting bias.It would steadly climb on its own.I resoldered everything on the mainboard.Even replaced a bunch of caps,and resistors.Nothing would fix it.Finally I read somewhere on the internet that it was the mainboards circuitboard that was defective.The material in the mainboard that would conduct and act as a conductor.So I decided to retire it away in the closet.A new circuitboard wasnt available at the time.The only way to get a replacement board was to ship it to England,or take it to England,and they would replace the board while you waited.But they would ship you a new board.So I decided to buy another brand amp.It didnt sound as good,but at least I could play my guitar.Finally I got tired of the bad sound from the other brand amp,and decided to buy another dsl100.So I bought another one from Guitar center in 2005.Anyway to make a long story short.I kept checking to see if a new board would become available.It did.But I couldnt order it directly from the distrubutor.I had to order it from a retailer.Once I received the board,I changed it out,and the problem went away.I also read that the 2005 model was also suseptable to going bad.So I bought another new board as a spare.I also checked the bios for drifting.It does drift after a couple of hours of playing.But not enough to go way out of range.But I suspect eventually it will go bad.because the new boards bias is rock solid,and doesnt drift the least.I havent played much in a few years.But I want to replace that board before it actually goes.Since I still have the new board.But you know how difficult it is to unplug all those connectors,and mark everything.I definetly had taken photos before I removed it before,so I would know if they were on correctly.I also had marked everything with tape.

I have a TSL 100 I bought from a guy who used it in a studio. He has many different Marshall heads, so I doubt he used this one much at all. He bought it about 15 years ago and never changed the tubes. I checked the bias and it was at 90mV both sides, as expected. I adjusted them down to 75mV to try and extend their life. It played well on low volume (VFR engaged), but today I cracked the volume, but only about 25%, and the HT fuse blew! No burned components I could see, but one of the power tubes looks toasted. The EHX labels on them are all different shades of green, with the suspected one wiping off as dust (overheated?). Would too low bias cause a tube to burn too hot? Or, is this just possibly from the tubes being old and only now getting use? (I play in a metal band. Luckily, thus didn't happen before our last gig)

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

I'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 .

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

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.

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

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

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.

Excellent episode. But, you never made mention, or returned to the disconnected reverb. Out of sheer morbid curiosity, I was wondering why you chose not to address it after its discovery?

These boards are notorious for bias drift issues. Board builds various creeping paths such as between B+ and Bias feed voltage - on the right most Screen Resistor. Also on the sockets themselfs and the PI circuit. Im actually rather surprised here that one of the 1 ohm resistors was shot. In order to shoot out a 1 Ohm 2 Watts resistor you need relatively high amperage / engergy which is unlikely to flow in a tube between Anode to cathode as they have a very high series Resistance, even when turned full on. At the same time, even if the heater to cathode would short - where enough energy is available, its still only virtually grounded via 2 100 Ohm Resistors. So there again is not a huge energy to be expected. Anyway... what i find strange is that i had worked on a couple of DSL / TSL (reworking boards, swapping boards and so on) and in 70 percent of cases i would say i had ark over in one tube aswell. What i find interesting is that its always the same socket 3 so as you had in your amp. Nice video. Thanks for that

Lots of Marshalls are like this. Either replace it with the final 'issue' board, or you'll keep having problems, in many cases. The new issues are simply because they messed up...they didn't issue a new board because the old ones worked.

I know this is a two year old video and i really appreciate Brad's videos...yes here comes the big 'however' this scenario is clearly nothing more than an intermittently shorting EL34. I've worked I dozens of these TSL and DSL's and this is a very common scenario. I'll bet if you had rapped on that one EL34 you Wurlys have seen major sparks as the weakened elements shorted together. Nice walk through taking one apart for those who han hadn't. BTW i heard of the rumor of conductive boards in these amps and after repairing literally dozens of the i never found that to be true. Nicely done video as usual..

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

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

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.

Your chuckle after going through all the connectors and wires to remove the bottom board was hilarious lol. I do not have a marshall amp like that and had no need to watch it lol I picked up a 1961 Electrohome made in Canada 3W four tube Portable Record Player that looks like a suitcase on kijiji for 20 bucks. Plus the guy delivered it lol. It just humms like a mother effer. Level knob does nothing. Balance knob does nothing. Bass and Treble Both seem to do something. No noise without tubes in it. Just wondering if that could be a output transformer issue? I don't have a tube tester but ordering tubes now. All the electronics look pristine. When you open up the case it smells like an old mans cabin. Love from Canada :)

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

Question: how do I send my DSL to you because honestly I have no interest in knowing the secret voodoo that you know that fixes these! I am hoping you still do repairs!

Do you like Older Marshall amps better. Pre ,900?

My biggest nightmare repair was a Marshall JCM2000, with a semi-conductive circuit board, it took me almost a month to figure out what was going on, but once I did, the repair only took less than an hour. It is what you don't know that will hurt you!

I’d assume that you have addressed this before, but what can you tell me about the ESR meter you used in this video. Home built? Commercially available? Thanks. BTW, I’ll put in my two cents on this generation of Marshall; Jim should have stopped with the 800 series. The TSL I worked on last year wasn’t much of a sonic revelation.

Run Bias Run. The board could be a blem board assembler at Marshall had on the shelf for a while. They were in a rush to move all these amps out of the factory for their newer counterparts called DSL which is the same as JCM 2000 I've read the second generation DSL100 from 2017 early ones that replaced jcm 2000 last years 2000ish suffered same issues. But the newer 2018 DSL 100's are way better Marshall fixed all the issues from customers complaints & added a few new features. Does the JVM series have same issue, Bias runaway?

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!

Thank you for posting this!! Could this the be cause of my sick DSL? I can't wait to find out! Geez, much cheaper than replacing the socket PCB... that I already spent money on :( Marshall doesn't include those plastic stand-offs with the new board and repurposing the orginals barely works :( Not even sure where I can get new ones. I need some!

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.

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

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..

My JCM 2000 DSL 100 is missing a few dial indicators so I have no idea what my settings are, two middle power amp tubes weren’t working so I pulled em’ out, green channel stays clean no matter how high the gain. My MG cabinet is too narrow for the amp head, so my half stack looks like a cross. It sounds freaking killer!!! I’m afraid to have it serviced. It might kill whatever mojo it has. Someone gave the amp to a guy in exchange for some Cocaine. He never came back to get it so it got passed around town and ended up with me, It’s ghetto fabulous!!

The little metal item in your driveway is a rocker switch common in guitar pedal switches. Usually in sets of 3. EHX often uses these stupid switches.. I've had to replace a couple of my own.

When the fuse blew it sounded like you dropped something nearby, causing something in the tube to rattle and short out causing it to spark. I'd be suspect of that tube, give it a few taps to test.

I caught that little bit o Slayer.....:)

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