JMI VOX AC30 Motor Boating on Normal Channel - Help

[cluster]

Yes there's a 25uF 25V cathode bypass cap, but also a 32uF B+ de-coupling cap; its voltage rating should be somewhat higher than the static VB+ across the reservoir cap.
Best to be ~1.4 x that, in case it's powered up without any el84 in place, so the 450V rating seems good to me (320 x 1.414 = 452)

Ok, I see it now. It wasn't obvious that it was an electrolytic cap.

[cluster]

I just want to be sure there's no mistake here. The caps purpose as a filter/decoupling cap as well as it's purpose as a cathode circuit bypass cap have both been used. I think it's a filter cap. In which case the schematic specs 32uf (probably why it was 33uf) and also why there was an oscillation problem when it wasn't grounded. If it were a cathode bypass cap I don't think the builder would have used the spec in both voltage rating and uf value and I don't think that a ground fault would cause oscillation, ergo, connecting the ground shouldn't have stopped the oscillation. Further, the spec for the cathode bypass cap is indeed 25uf and doesn't need to be 450V. And the builder wouldn't have used that voltage rating and as noted any reasonable value and even some unreasonable ones could be used. What I'm not understanding is why this cap in question with the busted lead that caused oscillation is being called the cathode bypass cap and the concern of 22uf vs 25uf has been raised. I'm pretty sure we should be discussing the 33uf/450V filter cap that caused the problem. Where did things get confused here?

Your right, There was some confusion but I see it now. I used a 22uF 450v cap since that is what I had on hand. Hope that works. Too bad, that other cap was really nice.

[Chuck H]

22uf will be great. Not sure why 33uf was spec'd. Especially when much smaller value filters were used throughout the amp and in higher demand circuits. I can only speculate that it's what the designer had on hand when the "mod" was developed and they just spec'd the prototype value for manufacture.

[cluster]

Thank you to everyone. Your support is truly appreciated.