Marshall JTM30 output and bias question

[Enzo]

Bias not likely involved.

If it helps, the transformer is not partially bad, it is totally bad. it just isn't totally shorted up end to end or melted. The fact you can shove a small signal through it is about the same thing as driving your car with the parking brakes set. You can probably move the car, but not easily or well.

[Randall]

Customer is a real hand wringer, he's not going to want to hear that. Oh well. Luckily, it is available at CED if he wants to go that route.

Thanks fellows!

[Leo_Gnardo]

Could this be the case if one or two windings shorted? Could the bias issue causing the tubes to pull 96mA have caused this?

I'm thinking, could be. That primary wire is mighty thin, like fuse wire. 100 ish mA, more with signal, might have not been enough to cause the wire itself to melt, but its lacquer insulation, sure!

Transformer failures are often more clear cut: open circuit on a primary winding for instance. Work on enough amps, you'll run across cases similar to this Marshall. That's why I jump past the analysis stage when I suspect this kind of failure, and clip in whatever known working OT that's ready to hand. More power? Then it's time to place an order. Or pick one off the shelf if I'm lucky enough to have one in stock.

[g1]

That's actually not a bad price as far as Marshall OT's go.
Tell him the merc.mag. price first.