Hi: I know what you are going thru since I have
2 Fender Bassaman Heads circa 63 blonde and the silver like yours. I am a electrical engineer and
about the only source is "not" to go thru Fender nor ask because simply they do know and lost the schematics. I am having problems getting the schematices for my 76 twin reverb amp! No noblody knows anything so I just basically blind and diagnose the probs myself. I can tell you they you 6l6 tubes and the standard preamp 12Ax7 tubes.
I know what your going thru,also biasing is another "beast"! These amps have to be biased otherwise the tubes may produce an unplpleasant sound and run hot. The best thing to so to repolace tubes is buy "match Groove tubes" they
are equiped to selfbiasing. Better than the other alternative. Having "red hot" tubes. As far as, schematics I think there are books but I have not found the ones I would like. Bassically the tubes need to be changed and it is a debated subject of the period to this but the general rule of thumb is every 2-3 years maybe longer depending on how you use the freqency,that is. Other problems have to be done on a bench tester and rule out the culprit. Tubes in general will "tell" that they need changing by becoming less "harmaonic". Also
less output in the gridplates will deteriate,and a visable sign is if they glow yellow more than blue. Also another consideration, tubes are great
but they need to be changed in pairs. I hope this helps some. Bye Dave
Re: Fender Bassman & tube amp info
Hi: I know what you are going thru since I have
2 Fender Bassaman Heads circa 63 blonde and the silver like yours. I am a electrical engineer and
about the only source is "not" to go thru Fender nor ask because simply they do know and lost the schematics. I am having problems getting the schematices for my 76 twin reverb amp! No noblody knows anything so I just basically blind and diagnose the probs myself. I can tell you they you 6l6 tubes and the standard preamp 12Ax7 tubes.
I know what your going thru,also biasing is another "beast"! These amps have to be biased otherwise the tubes may produce an unplpleasant sound and run hot. The best thing to so to repolace tubes is buy "match Groove tubes" they
are equiped to selfbiasing. Better than the other alternative. Having "red hot" tubes. As far as, schematics I think there are books but I have not found the ones I would like. Bassically the tubes need to be changed and it is a debated subject of the period to this but the general rule of thumb is every 2-3 years maybe longer depending on how you use the freqency,that is. Other problems have to be done on a bench tester and rule out the culprit. Tubes in general will "tell" that they need changing by becoming less "harmaonic". Also
less output in the gridplates will deteriate,and a visable sign is if they glow yellow more than blue. Also another consideration, tubes are great
but they need to be changed in pairs. I hope this helps some. Bye Dave