Marshall 2150: no heater current

[Laurent Brondel]

The amp was working and sounding great, today turning the amp on, power switch lights up but tubes don't. I checked all the fuses for continuity, all good. No AC voltage between the heater wires. I've never faced that issue before on any amp and would be grateful for any idea!

[pompeiisneaks]

you might want to pull all tubes and check again. If there's still no ac voltage on the heaters at that point, then there could be something wrong with either the transformer, or the connection between the transformer and those 4 fuses for the heaters. If there's AC after pulling tubes then one of the tubes may have gone bad and dead shorted to ground from a heater pin.

~Phil

[Laurent Brondel]

Thanks Phil, no AC with or without tubes.
I just unsoldered the PT heater wires from the fuses PCB to isolate any issue with the wiring and/or PCB, there's no AC voltage between them, center tap is connected to ground.
Is my PT gone? Is that something that can be fixed?

[pompeiisneaks]

If you're getting 0 ac output from the heater taps with nothing connected, but get B+ and other voltages, then it's possible the heater winding is shorted internally. You can definitely buy a separate heater transformer and install it, but if htat's gone, its also possible some other part of the amp is potentially going south. Are you still seeing 120/240 where ever you are with the input side?

~Phil

[sluckey]

Is my PT gone? Is that something that can be fixed?

PT is possibly bad. Check for AC voltage between F4 and F5. Then check AC voltage between F3 and ground.

[Laurent Brondel]

Yes, the power switch lights up, what else could I measure to check the PT?
The amp was working fine this morning, and then no more a few moments later when I turned it back on, no smoke, noise or anything burnt that I can detect, weird.

[Laurent Brondel]

So, with the mains on, when I turn standby on, meter on pin 3 of one of the power tubes sockets (no tubes in) after a 1kV surge, it goes to around 500v and then drops down slowly, I stopped looking at 27v.

[sluckey]

Check for AC voltage between F4 and F5. Then check AC voltage between F3 and ground.

[Laurent Brondel]

PT is possibly bad. Check for AC voltage between F4 and F5. Then check AC voltage between F3 and ground.

Thanks, I get nothing, no AC, between F4 and F5, and nothing either between F3 and ground.

[sluckey]

You need to find a replacement PT.

[Laurent Brondel]

You need to find a replacement PT.

Yeah, unfortunately… Any idea of how this PT died? I mean I get things work, and then don't, but the amp was working just fine.
This is a peculiar Marshall model briefly made, but it is a 100w model, mine has the US 4x 6550's and 3x 12ax7's, can I assume a replacement PT for 1959/2003 would work properly?

[sluckey]

can I assume a replacement PT for 1959/2003 would work properly?

Comparing the schematics, I'd say yes. But just because the electrical characteristics look the same does not mean the replacement will physically fit your amp. Time to post some pics of the PT with topside view and bottom side view.

[Reeltarded]

Standup replacement 2203. 1959 specific models are normally laydown.

[Laurent Brondel]

It looks pretty much the same as my '73 SL:

[sluckey]

I believe this will work...

https://www.hammfg.com/files/parts/pdf/290HX.pdf