Silverface Bassman 50 keeps blowing fuse

[PaulT28]

I have a silverface Bassman 50 with matching 2-15" cabinet and when I push it and get the volume up to get the tone I'm digging, it blows the 2amp fuse that is on the back. Is it safe to put a 3amp fuse in or is that a recipe for disaster? The first time it blew the fuse, I think one of the power tubes was loose and there was a short of some sort. This last time, everything was snug...no tubes loose. I can't figure it out. I'd just like to see if it is something simple before I take it in to get it opened up on the bench.

As far as the tubes, I don't think it is them because my tone is right there where it should be, no fluctuation of volume or tone which you'd typically see when the power tubes were throwing in the towel.

Am I pushing the amp too hard by cranking it to 10? Is it not made to run that loud? I just LOVE the sound I get when it's cranked...pure heaven.

Thanks in advance!

[rob S]

get it serviced.

[kafka]

Originally Posted by PaulT28

Is it safe to put a 3amp fuse in or is that a recipe for disaster?
...
Am I pushing the amp too hard by cranking it to 10? Is it not made to run that loud? I just LOVE the sound I get when it's cranked...pure heaven.

From the schematic I'm looking at, the Bassman 50 requires a 2 amp fuse. If you're blowing that, it indicates that something isn't right.

It could still be a bad tube, even if you're only experiencing the problem when you push it. It sounds like it may be biased too hot for that particular set of tubes, and when you push it, you're asking them to exceed their max rating. You may survive on these tubes a while longer, but once they start popping fuses, they're on their last legs. I'd recommending replacing them.

If you're adventurous, you can learn to set the bias yourself. There are plenty of guides on how to do this. Keep in mind that you're risking damage to your tubes and amp if you screw it up. Oh yeah, and if you have to open the amp to set the bias, you could kill yourself. But if you don't die from it and you succeed, you'll be that much smarter. So consider the options.

Otherwise, have a technician fix it for you.

[PaulT28]

Point taken, I'll just get a new set of tubes and have a qualifies tech rebias it. Also, you are correct, it is the 2A fuse that it blows. Thanks!

[GYMusic]

Shorted power supply rectifiers or power transformer.

[snüzz]

don't move up to a 3 amp fuse. that is a safety system you do not want to bypass.

[PaulT28]

Originally Posted by GYMusic

Shorted power supply rectifiers or power transformer.

I will be taking it in nonetheless to see if it is what you say, or simply the tubes needing to be replaced and rebiased. How much should a repair like this cost if it is simply new tubes and rebiasing?

If i need to fix shorted power supply rectifiers or get a new output transformer how much should that cost me?

I just want a ballpark so I know if I am getting a fair price when I get it taken in.

[FFTT]

Most shops charge $60-80.00 per hour for bench time.

Add for tubes and any other parts.