Jcm2000 bias drift fix

  • Thread starter Thread starter Meanjoegreene
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Meanjoegreene

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My 2002 100 watt apparently has it. It looks like the replacement boards are tough to get but I haven’t contacted Marshall yet.

Any suggestions welcome. I’ve moved on to other amps but when dialed in it’s killer too. I’d love to get it running again.
 
Meanjoegreene said:
My 2002 100 watt apparently has it. It looks like the replacement boards are tough to get but I haven’t contacted Marshall yet.

Any suggestions welcome. I’ve moved on to other amps but when dialed in it’s killer too. I’d love to get it running again.
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I believe you, but how do you know? Are you only going by the year or have you actually experienced it?
 
https://www.tubesandmore.com/products/board-marshall-replacement-jcm-2000-dsl-100

Looks like they are out of stock for now but I just did this to my DSL in December. Sounds great and solved the problem. Make sure to take plenty of pics of where the cables go or take pics in order of which cable you are disconnecting and reverse it when installing new board. It's very easy to do yourself. Should only take you 45 mins to do plus another 5 mins to re-bias amp. Nothing to it man.
 
Went thru a few tubes and minor repairs. I’ve got a friend that’s a good tech that I hate to bug but I did this time.

He took measurements…went from 70 to 90 after heating up a while
 
SgtThump said:
5



Thanks for the info.
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He was hoping something else but after fixing a few minor things he measured and recorded the numbers. I guess it just got progressively higher as the board heated up
 
Meanjoegreene said:
Went thru a few tubes and minor repairs. I’ve got a friend that’s a good tech that I hate to bug but I did this time.

He took measurements…went from 70 to 90 after heating up a while
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What happens when it heats up and the bias drifts? I have an amp that does some weird stuff when it gets good and warmed up.
 
Anyone compared the newer reissue DSLs to the old ones? Has this issue been addressed?
 
headlessdeadguy said:
What happens when it heats up and the bias drifts? I have an amp that does some weird stuff when it gets good and warmed up.
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Blows fuses and/or burns and red plates tubes

And it got progressively worse…like happens faster whereas before I was probably just wearing out tubes faster instead of blowing fuses and red plating
 
Soundstorm said:
Anyone compared the newer reissue DSLs to the old ones? Has this issue been addressed?
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Yes, the issues have been addressed with all "DSL" labeled models. Its only the JCM2000 series that has this issue.

As far as sound goes they are all ballpark close. JCM2000 is the most organic sounding to my ears. The latest model HR sounds like a modeler to me. Something about it sounds fake and plasticky. It sounds cool otherwise. Seems to have more upper mid content, harmonics seem to pop more and the adjustable resonance is a big plus vs the useless deep switch on the JCM2000.
 
PurityS.L.G said:
Yes, the issues have been addressed with all "DSL" labeled models. Its only the JCM2000 series that has this issue.

As far as sound goes they are all ballpark close. JCM2000 is the most organic sounding to my ears. The latest model HR sounds like a modeler to me. Something about it sounds fake and plasticky. It sounds cool otherwise. Seems to have more upper mid content, harmonics seem to pop more and the adjustable resonance is a big plus vs the useless deep switch on the JCM2000.
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The new ones sound more modern and less like the 2000's. I don't like them. I had a 100R for a couple weeks, and it just didn't have that MOJO the originals can.
 
Meanjoegreene said:
Yeah, and I have a sentimental attachment to that amp because it’s what I used for my favorite original music band back in the day…and also my first and favorite Marshall
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They are killer amps. I've owned several. I tend to look for 2004+, but the older ones with issues roar with the best of them!

Oddly enough, the old DSL was the first amp I got to learn how to bias myself.
 


Marshall fixed the JCM 2K PCB's 2005 and after.
The year of the head is usually in the bar code on the back panel.
The bias drift problem was mostly on the 100 watt DSL and not the 50 as it was a heat related issue.
Stay away from folks selling 90's & early 2000's 100 watt 2K amps. They're tainted. Not if but when they have problems.
Ive had a 2006 & 2009 still have the 09. Great amps.
 
I still love mine . It sounds really good. They to the jcm 2000s TSL 100 was list exactly like a dusk rectifier and boom it’s really incredible
 
Anyone looked into the Dr tube stable bias mod ? Looks like a company in the Netherlands.
 
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