JCM 2000 DSL 50 Bias Drift

[abkeller1]

Trying to sell my 2000 DSL 50. No one is biting. Ask what year it is. Mine is a 2000. They're worried about Bias Drift yet my amp runs perfectly and is 24 years old. What's the deal with the Bias Drift on the 50 watts. I thought only 100 watts. People seem scared to buy this amp

 

[nortiks]

Trying to sell my 2000 DSL 50. No one is biting. Ask what year it is. Mine is a 2000. They're worried about Bias Drift yet my amp runs perfectly and is 24 years old. What's the deal with the Bias Drift on the 50 watts. I thought only 100 watts. People seem scared to buy this amp

Last year I bought the same amp/year you have for sale and this is what I had to go through to get it working properly. Of course my experience does not mean that your amp has the same issues. But it does show that some do, plus there are other accounts of problem DSL50s floating around, and that's why people shun them I suppose. Plus amp prices are depressed right now anyway, making it worse. Maybe you can guarantee it doesn't have problems and do a 14 day return period to try to help alleviate peoples' concerns?

[edit] As for the 100 vs the 50, from what I understand the boards are the same, only populated differently. But I'm not 100% on that. But if so, then makes perfect sense that both might have the same problem (though might not).

 

[Leonard Neemoil]

Assure potential buyers that you've never had any problems. Maybe fix the speaker jack grounds before hand. Then, let them know about the stable bias kit if they're worried about the runaway bias that some DSL amps develop.

Depending on what you're selling it for, you might want to install the stable bias kit prior to sale. That, along with the speaker output fix, and providing online info (tons of it out there) should assure buyers that you're selling a completely reliable amp.

Those amps can be a real crap shoot, but with the mods mentioned above, they are as reliable as any other modern production amp afaik.

Let's see what others have to say, @guitarbilly74 seems to know a lot about these.

 

[guitarbilly74]

Depending on what you're selling it for, you might want to install the stable bias kit prior to sale. That, along with the speaker output fix, and providing online info (tons of it out there) should assure buyers that you're

Ultimately, I think that's the best course of action.

I've owned many (20+) JCM 2000 DSLs over the years, including many early ones and only 1 of them had the bias issue. Stock DSLs are used in concerts backlines everywhere and they're fine. I currently have a '98 with no issues.

So I don't believe the problem is as widespread as some seem to believe it is.

With that said, the fact is that regardless of whether it's warrantted or not, the notion that the early DSLs have bias problems is well known to buyers and many won't buy an earlier model.
Works for me, because I got several early ones at great prices over the years - and they all were fine (except one, but even that one was an easy fix).

But when it comes to sales, perception is reality, so consider getting the Dr Tube board and installing it. It will be about an $150 investment when it's all said and done (considerably less if you can do it yourself) but it makes your amp instantly more marketable. And maybe you can even recover some of that in the sales price, since saying the amp was "fixed/updated" will give you a bit more wiggle room with the price. People will pay $100-ish more for one that's been updated.

 

[guitarbilly74]

Another thing worth mentioning is that "recommended" bias setting by Marshall (90/side on the 100w and 45w/side on the 50w) is unnecessarily high for these amps.

I've always biased my DSL100s at 72/side (36/side for a 50w) and it is definitely enough and it actually sounds better than the suggested settings.
This is a preamp based amp for the most part, there is no need to bias them hot. And keeping the tubes cooler goes a long way at keeping these issues from happening.

 

[nortiks]

Ditto @guitarbilly74 comments on the kit fix. The bias drift part in my link to fixes (I linked someone else's video) is functionally the same as the kit. Takes more skill to implement and the finished job looks nicer, but it accomplishes the same thing in terms of what traces on the board are bypassed. The reason I did mine the way I did is because I wanted to get a fundamental understanding of the problem, and there is some mis-info floating around saying the kit is just snake oil. So not knowing for sure I passed on it, though now I can say with 100% confidence it does the same thing as what the fix in the guy's video I linked does, and is more straight-forward to install for most DIYers.

Ditto @guitarbilly74 again for the bias. And TBH, hot bias might in fact explain why some go bad and others not, imo. The root issue is the epoxy becomes slightly conductive when it gets cooked. What cooks it? Hot output tubes. So it only follows that if the output tubes are never to "epoxy cooking temp" the problem never manifests. And of course once the problem starts, the dog is chasing his tail at that point. The cooked board causes the tubes to overheat, which further cooks the board, which further causes the tubes to overheat....