Roast my schematic

[tubeswell]

Thanks for that handy link PRR - useful to know the various origins behind the tonestack names in the program.

[Opry Audio]

Hey! Just wanted to update y’all on this amp, it’s built and it works— kind of! Upon start up I heard some crackling coming from the PT, and a bit of smoke. It seems like there might be too big of a load on the PT, it’s getting pretty hot. Here’s a pic of the build. Just want to focus on a good power supply for now. Suggestions? I’m using a 10K 5W to drop voltage for the PI but it might be too much— on second thought it could be that the bias supply isn’t wired correctly too

https://ibb.co/jW5d4mF

[tubeswell]

Hey! Just wanted to update y’all on this amp, it’s built and it works— kind of! Upon start up I heard some crackling coming from the PT, and a bit of smoke. It seems like there might be too big of a load on the PT, it’s getting pretty hot. ...Suggestions? ...

You have a short somewhere on the secondary side of the PT which is pulling too much current through the PT.


This can happen for a number of possible reasons:

• some part of the B+/power rail/filter caps positive nodes/supply resistors is connecting to the chassis somehow, (possibly a long/unclipped lead or a solder run is touching the chassis behind an eyelet board)
• the reservoir cap/one of the filter caps is shorted and the HT is dumping current straight to ground,
• one end of the filament winding is connected to the chassis somehow (e.g. at the lamp holder?)
• Your rectifier is shorted and it has destroyed the reservoir cap causing a B+ short to ground
• etc

Look for the short.


If you are lucky, the PT might have survived already, but not all PTs can handle being run into a direct short.

So before proceeding further, you should disconnect all the PT secondaries and (carefully) AC-test them with insulated test clip leads on your VAC meter (and don't let the loose winding ends come into contact with anything that would electrocute anyone or short the PT)

[Opry Audio]

Yeah the transformer is no good. I just checked the secondary and there’s a short on the B+ line. That’s a huge bummer! But lesson learned I guess, dang! My can cap has a short in it