22-06-2021, 05:29 AM
Getting there but also encountered yet more problems. As you see from the pics it's all painted and pots/knobs fitted. I no longer have oscillation but do have leakage of signal between left & right channels. I suspect this is a ground issue or a bogup of wiring on my part. Grounding of stereo amps is tricky, in my case I've gone for each IP goes to each channels gain stage ground. This is slightly complicated by the cathodes followers on each IP, these are two triodes in one ECC82. Each CF is grounded separately instead of both triodes sharing a common ground as would usually be the case; this may the seat of the issue. Anyhoo, no biggy.
What is more of a problem is self induced PSU issues. The amp uses two tfmrs, one supplies HT & heater supply for both OP stages/CF-drivers & phase splitters. The other tfmr supplies a negative supply/bias, screen grid supply and IP/tone stage heater supply. I wound both tfmrs myself but have bogged up on the latter - the negative rail is sagging, should be -100v say -80v loaded,it's dropped to -62v. The regulated screen grid supply is also going into SC protection mode, probably a mistake on the PSU board.
I tested all these supplies but have obviously made a mistake or mistakes somewhere, ce la vie, I'll sort it but am suffering from a lack of enthusiasm at present so I've parked the amp out of the way for now and will drop back onto when I have a few other jobs/projects sorted. Anyroad,here's a few pics.
What is more of a problem is self induced PSU issues. The amp uses two tfmrs, one supplies HT & heater supply for both OP stages/CF-drivers & phase splitters. The other tfmr supplies a negative supply/bias, screen grid supply and IP/tone stage heater supply. I wound both tfmrs myself but have bogged up on the latter - the negative rail is sagging, should be -100v say -80v loaded,it's dropped to -62v. The regulated screen grid supply is also going into SC protection mode, probably a mistake on the PSU board.
I tested all these supplies but have obviously made a mistake or mistakes somewhere, ce la vie, I'll sort it but am suffering from a lack of enthusiasm at present so I've parked the amp out of the way for now and will drop back onto when I have a few other jobs/projects sorted. Anyroad,here's a few pics.
