27-06-2017, 04:51 AM
More fun and games and slightly better video quality ...
Tried to apply NFB today, but the amp didn't like it, see - https://youtu.be/QxWrAEf4G8U . This is odd as when it was a "prototype" I applied NFB with no bother. I got the same fault as before when it was mis behaving, IE the OPT was "squeeking". I can here the squeek coming from inside the shroud. Time to have a look inside methinks.
Tried various small caps (1000p ) from anode taps - primary of OPT to 43% taps and HT to anodes. No attenuation of fault. I'll get it on the big Tek scope tomorrow which has a higher range and is happier with a higher voltage IP.
One thing I noted whilst monitoring the neg bias of the OP stage was it went from - 35v to around - 100v. No idea if this is indicative. It's been suggested I swap over the PS OP, which I'll try today.
A.
Tried to apply NFB today, but the amp didn't like it, see - https://youtu.be/QxWrAEf4G8U . This is odd as when it was a "prototype" I applied NFB with no bother. I got the same fault as before when it was mis behaving, IE the OPT was "squeeking". I can here the squeek coming from inside the shroud. Time to have a look inside methinks.
Tried various small caps (1000p ) from anode taps - primary of OPT to 43% taps and HT to anodes. No attenuation of fault. I'll get it on the big Tek scope tomorrow which has a higher range and is happier with a higher voltage IP.
One thing I noted whilst monitoring the neg bias of the OP stage was it went from - 35v to around - 100v. No idea if this is indicative. It's been suggested I swap over the PS OP, which I'll try today.
A.
