Weber 8Cm100 questionable grounding

[nsubulysses]

This scenario seems weird to me. Please tell me if it is weird to you too.

I have an amp that is JCM800 clone. It has EL34s so pin 1 is tied to pin 8. This chain is tied to ground at the power supply filter cap ground node. The speaker jack is a cliff jack so its ground is tied to the pin 1 and pin 8 connection, connected to the chassis via the PS filter cap ground. Seems wrong to tie the speaker jack ground to the power supply ground, but I can't find anything that is a definitive yes or no on this.

When I got this amp it had many little errors in the build. No grid resistor on V1, PI plate load resistors reversed, speaker jack wiring had ground on the tip (why won't my scope read this???), seeming to all culminate in a bias problem and the PT was shorted on the primary.

I am posting this question because as far as I can tell the amp is works normally now, but the new PT does get pretty hot to the touch. Would hate to get this one back in a month or two with the PT damaged again.

[J M Fahey]

Maybe your power tubes are underbiased and pass too much idle current (any redplating visible if you turn lights off?).
I would ground speaker jacks straight to PSU caps with their own wires, and add 1 ohm current sensing resistors at each power tube, between pins 1-8 and ground, only way to make certain.

And the PT might simply be underspecīd .

alan0354 latest experiences with Weber PT werenīt exactly stellar.

[nsubulysses]

Yeah it was funny how Alan got all those bad PTs from Weber because he started talking about that the same day I got my delivery confirmation email from them. Damn.

Because of his thread I tested the PT with a meter first before installing it and I did get even voltages from the HT windings. No redplating that I can see, even when cranked into a dummy load. I have it biased to ~36mA at 430Vp. It does show a crossover notch. From what I've read about JCM800 bias this is normal, and although you can bump the bias hotter to get rid of the notch, it will be biased extremely hot to do this. I don't want to do this since the PT already burnt out once on this amp, and the PT is getting hot now even under what seems to be "normal" operation!

I will try the 1 ohm sensing resistors to corroberate my bias probe measures.

Maybe my error was buying another Weber PT. Or I'm missing osmethin else, or this is normal