Bad tubes and feedback?

**bcgvh** · 01.19.07, 03:20 AM

I just bought a used 5150 combo online and it just got here. The guy said it needed some new tubes as they are getting old and it obviously is in desperate need of them due to the tremendous drop in volume on the clean channel when I turned it on to test it out. There was also an uncontrollable amount of squeal and feedback coming from the distortion channel to the point where it was unplayable. Now I only played for a minute just to test this out to make sure nothing was severely damaged in shipping, and I also already know that it needs new tubes, but do bad tubes also cause this enormous amount of feedback?

**vhin04** · 01.19.07, 07:12 AM

Yes, if a tube has gone microphonic, or bad, it can screetch like a dying cat, or be the cause of the loss in volume. I would start by replacing the tubes and see if that fixes the problem. If it doesn't, then take it in to a good tech to have it serviced. 5150's are pretty sturdy and reliable amps, and if yours is in good condition, then it should be just tubes that need replacing.

AT · 01.19.07, 10:26 AM

Originally Posted by vhin04

Yes, if a tube has gone microphonic, or bad, it can screetch like a dying cat, or be the cause of the loss in volume. I would start by replacing the tubes and see if that fixes the problem. If it doesn't, then take it in to a good tech to have it serviced. 5150's are pretty sturdy and reliable amps, and if yours is in good condition, then it should be just tubes that need replacing.

Yes, and also, avoid playing it until you install new power tubes. If one is truly that bad, you don't want to cause problems with the socket of the other one.

I've replaced the power tubes in both my 5150 and 5150II with Electro-Harmonix tubes, and they've served me well.

**mk5** · 01.19.07, 12:05 PM

Preamp tubes are most likely the source of the issue. If you get power tubes as well, remember you can plug & play. don't worry about having to bias w/ Peaveys.

**tommywho5150** · 01.19.07, 12:51 PM

yup pretty much what everyone else has said, i used to only buy groove tubes for my 5150 but i just recently got given some sovtecs and to be honest im quite impressed its worth giving them a try mate as they are quite a bit cheaper.
also the squeeling could be down to a microphonic pickup in your guitar if it turns out the tube isnt to blame, its worth considering before u right the amp off or send it for costly repairs

AT · 01.19.07, 07:11 PM

Semi-related... I just picked up a 5150 combo today that was an eBay purchase. I hadn't ever planned to get one, but the price was right ($330)--probably because the guy didn't want to ship it. So instead I drove 15 minutes and probably saved a few hundred dollars.

And... the thing is damn big! So much for the idea of keeping it in my living room...