Right now my receiver is working pretty good but seems a little under-powered and is not incredible balanced channel to channel. I have a mismatched bunch of old untested 7355 power tubes (different brands), which I have balanced as well as the existing circuits allow. Plate dissipation is about 21 watts on Channel A and 19.5 on Channel B, both exceed the 7355 spec'd 18 watts rating. The existing circuits don't allow to lower/raise the bias of the push tube without rising/lowering the bias of the pull tube so all you can do is balance them. Because 7355 are too hard to find, I am going to change the tubes to 5881s, which are pinned out a little different but have very similar specs and 23 watt plate dissipation rating.
My question is this, the 5881 are slightly bigger around and while they fit in place, the clearance between the bottles and the output transformers is only about an 1/8" to 3/16"; the clearance with the 7355s is about 1/4" to 5/16". Is there going to be a heat problem with the output transformer that close to the power tubes ? Should I move them over to get a little more clearance?
My question is this, the 5881 are slightly bigger around and while they fit in place, the clearance between the bottles and the output transformers is only about an 1/8" to 3/16"; the clearance with the 7355s is about 1/4" to 5/16". Is there going to be a heat problem with the output transformer that close to the power tubes ? Should I move them over to get a little more clearance?
Perhaps a cheap 220 VAC fan on 120 VAC will improve things. You get air movement, without much noise.
BTW, Russian 6Π3C-E (6p3s-e) tubes are excellent 5881 equivalents.
BTW, Russian 6Π3C-E (6p3s-e) tubes are excellent 5881 equivalents.
I bought a matched set of the new Russian Tung Sol 5881 which are supposed to rival the old US tung-sols. I'll let you know how they sound when I get em running.
Vacuum Tube - 5881, Tung-Sol Reissue | Antique Electronic Supply
Vacuum Tube - 5881, Tung-Sol Reissue | Antique Electronic Supply