Grateful Dead Music Forum

I have an all tube 100 watt fender twin about 2 years old.

This just started happening a couple of days ago. I play for about 10 minutes then I get a very very loud vibrating electrical hum. I can no longer play though it and have to shut it down. Then it will work for just a short time.

one other clue, just before it happens I hear a couple of little pops. Not too loud.

Just to eliminate most possibilities I changed cables, guitars, outlets and used no pedals.

Any suggestions or thoughts?

The Pro-Tube series Twin has a known issue with the 2 breakaway PCB's. The one that the control pots mount to and the power amp board. There are roughly 20-25 little jumpers that connect both boards it to the various tube socket pins and to the main board. These fail from a combination of vibration and the wire being too thin. This might not be your problem but if a simple power tube change doesn't cure the problem then you're going to have to have a tech get in there with the chopsticks and see which one of those wires is on it's last strand.

Had the same issue with my Twin, sounds like your dealing with the exact same problem i had. Small crackling sound into a giant explosion of noise? Took it to amp tech, had a bad pre-amp tube changed it out now working just fine. Hope this helps.

Kick it! Kidding. Make sure your tech diagnoses the problem and you authorize prior to fixing.

Start with a tube change. If that don't fix it, keep your spare tubes and take it to a tech.

Here's a tip for you. While a few guitar shops do have a decent techie on staff, many will bs you 'til you're out of the store and call a local independent to pick your amp up & bring it back a week later. If you check around with a few of the working musicians in your area, they'll usually have the real dudes card in their wallet and you can arrange a personal meeting with the person you're gonna want to meet anyway if you keep using tube amps.

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Re: My amp is acting up on me!

New postby strumminsix on Fri Feb 13, 2009 11:29 am
Kick it!

Actually kicking or smacking the top of the amp has worked for me a few times...

I changed out the power tubes and it didnt help. I figured that it was either a power supply issue or more likely a connection or solder joint issue like jonarobb said.

Since it is only 2 years old that should be covered under fender's 5 year warranty. I am not really qualified to fix it so I took it to a tech. I just got back. I had to leave it. I'll let you know what happened.

deadguise wrote:

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Re: My amp is acting up on me!

New postby strumminsix on Fri Feb 13, 2009 11:29 am
Kick it!

Actually kicking or smacking the top of the amp has worked for me a few times...

It's possible a lucky hit might shift tubes in their sockets a bit, and that could conceivably cause the pins make better contact, but unless your last name is Fonzerrelli, a better way is to reach in the back(carefully, without burning yourself on hot tubes) and make sure all tubes are seated firmly in their sockets. Ideally this would be checked routinely prior to powering up the amp. Sometimes the springy brackets that secure the power tubes need to be tightened or scrunched down a bit, carefully: they will bend with a little care, but are slightly brittle and do occasionally snap.