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Old 06-30-2017, 02:26 AM   #1
dimar5150
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Default Amp feeding back badly

I have a 5150 III 50 watt head and tonight when I was playing on channel 3 it was feeding back horribly. even when muting the strings. Uncontrollable. I tried different guitars and bypassed my pedal board straight to the amp and still the same thing.
Are my tubes going bad? I tried the pencil trick on the tubes by tapping them but couldn't tell if they were micrphonic or not.

Anyone have experience with this problem?
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Old 06-30-2017, 06:27 AM   #2
PKVeazey
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I'm not familiar with your amp but it sounds like you've got really hot pickups and you forgot to turn the overdrive down. By overdrive, I mean if you have a master gain and a channel gain, the channel gain is overdriving and causing the problem. Then again, it's remotely possible that you have a 1960s Japanese junk guitar that's has those awful microphonic pickups that we used to laugh about because we could talk into the pickup and it would come out the amp. I doubt if that's the case.
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Old 06-30-2017, 10:52 AM   #3
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As PKVeazey says could be the guitar's pickups can you try an other guitar?
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Old 07-01-2017, 02:13 AM   #4
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I swapped all of my preamp tubes with new ones, still same issue. Tried 4 or 5 different guitars/ Then I fired up my mini 6505 tube amp and wouldn't you know, the same thing. Do you think it's interference of some type? I cant think of any new equipment I bought in my house that would cause it.
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Old 07-01-2017, 08:01 AM   #5
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I'm not trying to be funny, but have you tried turning the volume control to the left. I'm also assuming you don't have ANY pedals plugged in.
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Old 07-02-2017, 12:54 AM   #6
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Quote:
Originally Posted by PKVeazey View Post
I'm not trying to be funny, but have you tried turning the volume control to the left. I'm also assuming you don't have ANY pedals plugged in.
No pedals. Volume adjustments made. Getting horrible buzzing too with all different guitars (I own 17) and both amps. It's definitely something as far as interference wither with my house wiring or something maybe a neighbor is doing.
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Old 07-07-2017, 04:19 PM   #7
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Plug it into a different outlet---you may just have a loose ground on that one. Another possibility is cell phone interference---a friend of mine has a phone that can't be within 3 feet of any part of the signal chain. We spent an hour chasing our tails trying to figure out where the hideous howling was coming from---when he stepped outside to take a phone call everything went back to normal---now he just turns his phone off, or leaves it in the car!
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Old 07-08-2017, 12:38 AM   #8
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Quote:
Originally Posted by hippychip View Post
Plug it into a different outlet---you may just have a loose ground on that one. Another possibility is cell phone interference---a friend of mine has a phone that can't be within 3 feet of any part of the signal chain. We spent an hour chasing our tails trying to figure out where the hideous howling was coming from---when he stepped outside to take a phone call everything went back to normal---now he just turns his phone off, or leaves it in the car!
Just to add to Hippychip's comment about both. If you're going to plug the amp into a different outlet, make sure that it's not on the same circuit as the other outlets.

For Ontario codes, one circuit (30-60 amp Fuse) can supply up to (12) 120V outlets. So, if there is an interference issue with that one circuit that starts with the fuse box, in-line outlets on that circuit will carry the same issue (Assuming it's a grounding issue at the box for that circuit.)

Try the amp on a totally different circuit (Another floor if possible or another house for that matter). If changing circuits in your home does not solve the issue and changing homes does, the problem is at your electrical box and should be addressed by a qualified/certified electrician.

If changing homes and the issue continues, it's the amp itself that has to be looked at.

As to cell phones, yeah. They make more of a Morse Code buzzing sound when to close to tubes.
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Old 07-08-2017, 04:00 PM   #9
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The cell phone interference we were experiencing was nothing like morse code---I'm talking about humming, buzzing, and howling depending on where the phone was in the room---and no tube amps were involved!
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Old 07-09-2017, 08:25 AM   #10
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One last comment on this: You said you plugged into channel 3 and it squealed. What about the other channels? If its just that channel, the Volume control knob could be shorted and then you couldn't turn up or down because it would be wide open no matter where you turned it. If its not that, then the problems is probably right at the input jack. Everything I just said is meaningless if your other amp is doing the same thing. The only thing you didn't say was if you tried a different guitar cable. I've seen amps go wide open and it usually can be figured out. The second amp doing the same thing just blows everything out of the water.
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