This was a defective board material problem that caused cross conduction, manifesting over time with heat, most likely supplier QC. I have repaired many. A lot of techs tried to lift bias circuitry off the board which did solve the bias drift issue. Usually the next thing to happen was ingress of hum. This was cross talk from DC heater bridge rectifier to adjoining high impedance circuitry. There is only one fix - a new board.

And they sound incredible 👍🏻

they are good sounding amps that gig well especially the tsl with three channels

Haha we all have a Lyle chapter in our troubleshooting notebooks.

@@luthiervandros I've seen you lurking. Your username always gives me a chuckle.

@@IamtheFerryMan 🤜🏼🤛🏼😂

Just say no to rack mount boogies

Oh, you're quite right. I mentioned that I would after the rework is done, though I didn't show if.

That's why the big name, arena acts have two or three full stacks on stage. In most cases, they're only using one at a time and the others are backups.

It’s almost 100% cost driven in mass produced amps. All other rules as far as PCB layout still apply. You’re frequently dealing with high voltage, relative to other audio frequency devices, so dielectric parameters and trace spacing are your top concerns. Be mindful of trace width and routing when it comes to heater circuits. Use tools available to generate the DRC parameters in your ECAD software and guide your component placement and routing. Be mindful of thermals, too.

Well, first, the DSL100H is a different (much better) amp than the older JCM2000 model here. So that’s good. But I don’t know what’s going on in the switching of your model. Contact Marshall to get the suitable foot controller.

No. Vibration has nothing to do with heat. It stresses the leads/solder joints.

In most amps I would have. But the earlier DSL boards have drifting bias issues due to substandard board materials. The original board here was one of those. The replacement board doesn't have the faulty fiberglass. This should have been a worldwide recall under warranty.

@@PsionicAudio ooh yes forgot about that problem... Not much to do, other than New pcb

@@PsionicAudio How can I identify if mine has the old or new board? Mine is the DSL100H, not the older JCM2000 dual super lead. Getting ready to open mine up for maintenance.

@@g3ultra If you have a DSL100H,you dont have anything to worry about.This amp is the JCM2000 series of amps.Made from 1998-2005.There were a small number of late 1997 amps too.The new board fixes the problem.But they recommend replacing the tubes at the same time because they might be damaged from the drifting bias.

If it's a 500V cap, yes. 1KV, probably not.

@@PsionicAudio thank you. Love your content. Really great info and watching you wrestle the camera is a great time!

For sure I heard him say one of the complaints was crackling.

Also, regardless of the material used, circuit boards can become conductive, perhaps permanently, if a capacitor leaks. Tube circuits, being high impedance, are particularly susceptible to noise and bias drift from conductive boards (and double-sided boards are the worst). Solid-state circuit boards are more forgiving ---- I have successfully scrubbed cap leakage off of the (single-sided) PCB's for many vintage solid-state hifi receivers and amplifiers, and replaced the electrolyte-corroded parts, and gotten them working again, reliably. I don't know how old that failed Marshall DSL is, but if it's less than 6 to 8 years old, I would have recommended upgrading the new board before installation by changing out (at minimum) the two large filter caps which had obviously bulged and leaked on the the old board. Find another better-made brand of electrolytic cap to put in there, perhaps with a higher-voltage rating, if that's possible. Checking the rest of the old electrolytic caps with an ESR meter would identify any others that ought to be prophylactically changed on the replacement board. BTW, the only solid-state hifi gear I've ever worked on where merely cleaning capacitor leakage off of the circuit board isn't sufficient to fix the amp is some older models of Adcom amplifiers; the tarry brown leakage from the stock capacitors resembles tobacco juice, smells like fish when heated by the soldering iron, and is not only conductive but highly corrosive---- and it seeps into all the component-lead holes in the board and corrodes the solder joints where you can't see it. Plus, it causes leakage paths around an input IC, and after fixing all the other problems you had to cut a bunch of circuit board foils and lift several IC pins and associated resistors off of the board and reroute the circuit with flying leads.

Depends on the era. I've been a tech for 25 years and a MKIII owner for +30...its never needed not1 single repair. It's still on the original caps!

@@dan_perry Have you seen the inside of newer Mesas?

@@shckltnebay yes, I have. That's why I said certain era Boogies are better than others.

@@dan_perry Bought two Express series 550 and 525 with issues recently and no way is a normal tech going to be able to work one them

@@shckltnebay I agree. I was never a fan of that line. The Dual Calibur (DC5 & 10, not the DC3) series and .50 Cal, which came before those were much better made.

The original board was made of conductive material. It was not salvageable. Marshall should do a lot better by their customers.

There is an aftermarket bias kit you can buy which involves isolating the G1 pins from the board (cutting the pcb around the pin) and flying leads to them. That is the only way to make the existing board reliable again. Mar$hall could just not build chintzy junk and we wouldn't need to resort to such tactics...

@@Gtrtech It seems more prevalent the amp companies are having to skimp in order to make a buck, but others do that just because they can. It doesn't leave repair techs with nice thoughts about some of their products.