Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dwp on August 30, 2010, 01:09:53 pm

Title: another BF fender PT overheating, or is it?
Post by: dwp on August 30, 2010, 01:09:53 pm

I know I asked this a while back and got some assurance, a Fender BF Super Reverb trannie getting hot, now I just did it again.
     I converted a 65 Re-issue Twin Reverb to Tweed/5F6A-5E8A spec, with Tubenit's one tube reverb, and a switchable EF86 channel. One less preamp tube overall. The power X-frmr gets hot, very hot. not melting tar or burning your hand hot, but it still is alittle alarming.
     I just still wonder is there anything more driving about a Tweed circuit? the output tubes seem to be wired the same as typical blackface, am not sure though what the re-issue board was doing. I am running 460VDC to the output tubes, with -54VDC to bring the bias down to 35-38MV.
     Anybody got any comparible expperiences with happy ending I hope?
Thanks in advance, dwp

note: I meant 5F8A above. My dropping resistors are in line with bassman, 4.7K, then 10K, in lieu of 1K then 4.7K, this an issue?

Title: Re: another BF fender PT overheating, or is it?
Post by: eleventeen on August 30, 2010, 11:01:51 pm

Transformers, especially those operating right next to power tubes & rectifiers, can run hotter than you can touch under perfectly normal conditions. Not "leave skin behind" hot like a 5Y3 or 5U4 or EL34 that's been on for 30+ minutes...but definitely quite hot.