Tube amp blowing fuses

David Cook · Post by **David Cook** » 25 May 2017 10:28 am

Help, My 20 watt Jet 20 Ampeg tube amp keeps blowing fuses.. Any suggestions?

Thanks

Jack Stoner · Post by **Jack Stoner** » 25 May 2017 11:08 am

Hard to tell from your description. Could be a tube (if it is most likely the power tube(s). Could be power supply, filter caps, rectifier. Just too many possibilities. Best option is take it to an amp repair tech.

David Cook · Post by **David Cook** » 25 May 2017 11:38 am

Thanks Jack,

The light stays on until I turn on the standby

Ken Fox · Post by **Ken Fox** » 25 May 2017 12:38 pm

Pull the power tubes and try it again. Looks like it has 2 each 6V6 power tubes.

Dave Meis · Post by **Dave Meis** » 25 May 2017 11:00 pm

Had that happen just a few weeks ago on my Fender Bandmaster. Shorted out power tube. Swapped 'em out, good to go. Good luck.

Ken Fox · Post by **Ken Fox** » 26 May 2017 4:34 am

A lot of times a shorted power tube can take out the screen grid resistor at the power tube socket, 470 ohms in the case of Fender amps. When that happens that tube will not pass audio until the resistor is replaced. Just a passing thought!

Jay Ganz · Post by **Jay Ganz** » 26 May 2017 5:22 am

Also...if the capacitor on the input grid of a 6V6 tube starts leaking, it throws off the bias voltage
and the tube will start to glow red inside from excess current draw...then the fuse pops.
Got that?

Ken Fox · Post by **Ken Fox** » 26 May 2017 5:26 am

So true, Jay. Seen that and forgot to mention it.

Jay Ganz · Post by **Jay Ganz** » 26 May 2017 5:34 am

Guess it depends on whether it blows the fuse instantly or it takes a minute or so.
That will point out if it's just a short in the power supply itself.

Jack Stoner · Post by **Jack Stoner** » 26 May 2017 7:14 am

I don't remember on a 6V6 but on the Fender's with 6L6's the 470 ohm Screen Grid resistors will go and can also cause fuses to pop.

Bill Hatcher · Post by **Bill Hatcher** » 26 May 2017 12:25 pm

blows fuse and then blows more fuses.....you have a problem.

old amp?....filter caps. power tubes and the rectifier tube. swap the tubes and see if it blows. if not...problem solved. if so...filter caps. they need changing anyway....

David Cook · Post by **David Cook** » 2 Jun 2017 6:33 pm

Thanks everyone for the replies. I took it to a tech and he said it was the rectifier tube. This is a 2 year old amp

James Phillips · Post by **James Phillips** » 3 Jun 2017 5:31 am

David Cook wrote:Thanks everyone for the replies. I took it to a tech and he said it was the rectifier tube. This is a 2 year old amp

You could buy one of these from Weber ,, https://www.tedweber.com/wz34
They are nice to have around for trouble shooting ,or to replace that tube all together.
Good thing to have in your gig bag,too.

Jim Sliff · Post by **Jim Sliff** » 4 Jun 2017 7:50 pm

Got to the thread late - the tech was undoubtedly right. That's the most common reason.

David Cook · Post by **David Cook** » 11 Jun 2017 5:57 pm

Will I have to readjust the bias if I install the Copper cap to replace the rectifier tube?