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Marshall JCM 2000 DSL Main board swap PCB bias drift repair
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- Опубліковано 5 сер 2024
- I am kidding about the metal back. They're always missing.
My bands :
www.unrealcity.bandcamp.com
www.gloriousdescent.bandcamp.com
Replacement Board :
britishaudio.com/products/mar...
RJD guitar parts emporium :
www.ebay.com/sch/stigatsu/m.html
www.subversivecraft.com
I love Brad’s guitar garage and Psionic Audio. Brad cracks me up. Knows a thing or two about amps too.
"scratching the surface with a butterknife, did not fix the problem no... No, no..." That got me. Currently battling one of these bastards.
Get the replacement board and you should be good.
I replaced my board on my DSL 100 successfully a few years ago,The connectors were a nightmare,I had to label each one,and take a photo of the main board.The two 16 ohm outputs on the back of the amp,The shield side of the connector contact can wear out eventually leaving the 8 ohm output without a ground.The remedy is to solder the shielded side to ground,So if the 16 ohm connector loses contact with ground,the wire stills allows a ground on the 8 ohm connector,If the 16 ohm connector wears out and goes open.The output transformer will blow,you essentially have an open shield 8 ohm output.I still have another DSL 100 that I own to change the mainboard out,Ive had the board for a few years.I will change it out eventually.
The PCB Board is the problem they become conductive when they get warm and after that the bias runs out of control leading to tube and board failure. Tube Doctor do an add-on unit which was £40 plus you will need a mini hole drill. There is a guy on UA-cam showing you how to do this and has a good result. The second option is what you are doing as it should give you a new amp, I think it really depends on the use and how much you want to spend. On the up note if you want to sell it in the future you are much more likely to get a good price if the do a proper job with the right bits plus pictures as proof. They are great sounding amps I have two TSL122's which had to be rebuilt by Marshall under warranty. I don't know what issue board they used in mine but I do know the final good board is issue 20.
Ive seen the stable bias mods fail. The whole board becomes a ground plane and everything unites in a fireworks display. Doesn’t really matter where the bias circuits located if all other circuits become one. Your mileage may vary but not changing that board out is a bad idea. The modded boards sometimes take out the transformers when they go too. This amp for instance ate its power and output trannies. Rev 20 is the way to go or else you are literally playing with fire. If you like watching the process Ive done this 3 other times to my other 2000s check my other vids.
Were you able to fix the Ampeg VL-502/1002? I have a 502 waiting for me to fix the common issue (that crappy plastic connector that burns out).
I have a 503 and 1002. 503 has been a nightmare. 1002 has had multiple faults. I did the wiring mod. 50 watt models aren’t as prone with half the draw. I have had to replace screens, reverb cables, LDR’s, tubes. Right now I’m bypassing the impedance switch and seeing if it behaves. At wits end with it. Sounds great when it works.
I hope it sticks, my jvm repair has worked so far but these amps are not well designed in terms of pcb consistency
Thanks man. I'm bruised from the abuse this and that ampeg have dished out on me. Amps been killer so far. Might buy it off my buddy. Fingers crossed.
@@subversivecraft did you watch my JVM video? I worked on that amp several times before finally isolating those pins. It was definitely a last resort.... The customer is still rocking it though, so I think you are good.
@@jloewenheim I did see your video! I wasn't aware the JVM's had an issue too. Good to know, will pass on them. The original 2k board was modded to have the pins isolated and some traces cut to help prevent the issue. It didn't work because the board was conductive and incurred resistance with heat. Junk. Mod was expensive when it was done.
@@subversivecraft Again, hopefully, it sticks. The diameter FR4 used on these was a bad choice by Marshall in all of those amps. IMHO, the best option is to pull the boards, keep the transformers, and then insert a turret board and wire up as a hot-rodded Plexi or JCM 800.
Where did you buy the replacement board from?
Link in the description
Thank you!
I tracked down the dagnall company. ( under a different name etc ) now but they're were more than happy to replace and of the old dagnall transformers I wanted. They've got all the NOS marahall shit I asked for.
Turf-green keeps the conscience clean.
marshall super disaster
I typed in "what is the biggest piece of shit amp ever"
The answer is both.
the board you replaced it with will also fail, its not the most up to date one just the same board made later
It's a shame they are a piece of shit because when they are running OK they sound decent. The problem is......there isn't a good standard unit out there as they were bad from the factory.
Fact. Can confirm amp sounds amazing after board swap. No more power tubes red plating.
@@subversivecraft now it's repaired it will be a decent workhorse 👍