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Question on the SF Champ circuit.

xinu

Member
Messages
60
I being recapping and tubing my Silver Face Champ AA764 and noticed what looks like a 25pF cap across the 6V6's cathode and grid (pins 5 & 8). This capacitor is not shown in the schematics I've seen.

Could this be a later revision or mod to bleed-off higher frequencies or potential RF interference? I did a quick test and it doesn't seem to make a difference in or out of circuit.

Thanks,

Greg
 

HawkeyeKane

Member
Messages
1,325
Hmmm....seems like I've seen that done in another SE 6V6 amp myself, but I can't put my finger on which one. I think you may be on the right track with the treble bleed-off theory though. Have you always owned the amp? Could it have possibly been a previous owner's mod?

And have you checked to see if the cap is any good? If it's bad, it might lend itself as to why there's no discernable difference with and without it in place. Is there a cathode bypass cap in place?
 

wyatt

Member
Messages
4,168
Snubber cap.

CBS started using them as the lead dress got worse and they had more issues with noise. I don't think they ever put them on the schematics.
 

xinu

Member
Messages
60
It's relatively new to me and could have been a previous mod although the cap, as small as it is, has the crusty aged look to it.

Good thought on being open though. I could replace it but I kinda would like to know what it's doing there. It could be a CBS tweak for something.
 






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