Oscillating noise problem with Acoustic amp

[pdf64]

Ok, in the light of that, my guess is that the vactrols may be fine, rather the issue is that the ecap on the 400V HT node is failing, ie excessive ESR.

[Phil_S]

As an amateur, I'm not feeling very qualified to advise further on the question. I happen to have some experience dealing with an incandescent driven tremolo circuit on an old Gibson amp that I have and that is why I was able to offer some comments.

I am writing to simply say that obtaining a direct replacement Vactrol will be nearly impossible. It is my understanding that the ones with incandescent lamps are no longer made. I would do everything I could to avoid damaging the ones you have. In particular, I would only remove them for testing as a last resort.

[chikov]

Ok, in the light of that, my guess is that the vactrols may be fine, rather the issue is that the ecap on the 400V HT node is failing, ie excessive ESR.

To my great shame, I did not check the filtering capacitors. The very first two ones that were part of the Can capacitor are completely dead... I will go ahead and check the rest of them and replace them in a prompt manner. I have to admit I did learn a great deal about this amp and mysterious Vactrols. I will keep you posted on the results. Thank you so very much

[chikov]

I would like to thank all of you who helped me with this problem. I just installed two capacitors instead of that old Dual can capacitor that was completely dead and the amp works wonderfully now. I learned my lessons and will pay forward one way or another.