67 bassman tranny loud on standby

[pauluxy valley]

I scored a 67 bf bassman head (ab165) at a garage sale. Its all there sans 1 tube shield. Pulled the tubes pluged it in when I switched it to standby the tranny made a loud noise flip it back everthing is fine. Should I be concerned? Without load A+ is 490

[Albert Kreuzer]

Probably the filter caps are bad and drawing too much current.

[pauluxy valley]

Thanks I'll dig into it and test and replace those.

[Albert Kreuzer]

While you're in there, replace ALL the brown paper electrolytics - the filter caps under the doghouse, the bias cap (go for a 100V type instead of the 50) and the preamp cathode caps (you can use two single 22µ/25V instead of the duals).
Also look for loose transformer bolts (which can add to the hum).

[stokes]

Are you saying the hum is there when the switch is in standby or when it is "on" or "play"?

[pauluxy valley]

at first I thought it wa when it was on standby but now I know its when its on play
The loud tranny noise is gone
So far
replaced filter caps with stuff on hand (I'll order Atoms Later)
electrolytics in preamp
Tightened up tranny It was real loose
stuck tubes in it sounded bad
one power tube was glowing red
looks like I need to work on the bias supply
planing on converting to a 64bf

[stokes]

You say one tube is redplating,you are aware that this amp has a bias balance and not a bias adjust control?Did you only change the preamp electros?If so,I would be more concerned with the main filters,all of them should be changed because of their age,but you will get a quieter improvement with fresh main and screen caps,but as Albert already stated,all electros should be changed.

[pauluxy valley]

All the main filter caps are replaced the only electro that has not been replaced is the bias filter didn't have one on hand that would work for that the tube that was redplating was the fixed bias tube I'm going to convert it to ajustable biasand replace all the resistors they looked kinda cooked.

[stokes]

They are both "fixed bias tubes".The pot "balances" the bias so you dont have to use matched output tubes.If only one tube is redplating,it can likely be solved by tweaking this knob and balncing the bias so both tubes draw the same current.I am assuming you have too little bias voltage on the tube that is redplating.

[pauluxy valley]

Well fellas its sounding good now but I have one more question this thing was sitting in a storage shed for over 10 years the tolex cleaned up fairly well but all the hardware is rusty and pitted. Should I buy replacement hardware or just leave the original in place.