1968 Fender Bassman Silverface help

[Oren Hudson]

I powered up this head on the other day for the first time in a while and it popped the fuse. Put another one in and it did the same thing. It's never done this before. Any clues right off as to the possible problem?

[Bassmec]

Originally Posted by Oren Hudson

I powered up this head on the other day for the first time in a while and it popped the fuse. Put another one in and it did the same thing. It's never done this before. Any clues right off as to the possible problem?

Take out the output tubes and try again if the fuse don't fail now we are looking at output tubes, if it still blows disconnect the dc to the output trans if it still blows you have a power supply fault.
Valve amps are great and so easy to fix.
Don't blow yourself up with it though.

[MAMMOTHvolume]

would take it to a tech rather than try and do it yourself

[77PBass]

Given the value of the amp and your experience diagnosing tube amp issues, I would take it to a reputable tech. Depending on when it was serviced last and what was done, it could cost anywhere from $25 to $150 or more depneding on parts and service cost.

The good news is your power transformer is working. That is one of the most expensive parts to replace.

[AwkwardLoudness]

Yeah, I agree that you should consult an amp technician after checking for a loose power tube.

The possible problems include a loose power tube, failed power tube, failed filter capacitor, a fractured solder joint, or failed resistor in the power section.

[rickdog]

Originally Posted by Oren Hudson

I powered up this head on the other day for the first time in a while and it popped the fuse. Put another one in and it did the same thing.

How long is "in a while"? A power supply capacitor may have failed, old electrolytic caps gradually break down, especially if they're left unused for a long time. The amp is 40+ years old, has it ever been recapped?

[BassmanPaul]

Originally Posted by rickdog

How long is "in a while"? A power supply capacitor may have failed, old electrolytic caps gradually break down, especially if they're left unused for a long time. The amp is 40+ years old, has it ever been recapped?

That was my initial thought too. Amps that haven't been powered up in a long while should be brought up to working voltage slowly using a variac. This will allow the dielectrics in the caps to reform.