#1
So today I turned on my amp, let the tubes warm up for a minute or so just like always, then started checking my tuning, playing some cleans. Then I kicked on my reverb pedal and the amp jumped into this "fire-siren" sound - WAY louder than what the volume was set for. So I quickly shut everything down.

First thing I thought was that maybe a tube went bad, so I looked at the tubes while it was on standby, and they were all glowing. Flicked standby off and watched them for all I could stand, and then shut it down again. The tubes looked fine.

So I then thought I should eliminate all the variables. I disconnected the reverb (and the effects loop), so it was just my guitar into the amp. Turned it on - and everything sounded perfect.

So then, I thought, maybe the effects loop or the pedal? I hooked up a short 6" pedal cable to the send and return jacks of the effects loop, and again, the amp sounded fine. Then I tried the pedal again, but just with two 6" cables into the effects loop - not the longer cables I usually use. Everything worked fine.

Anyway, my question is - could it be one of my longer cables causing this problem? I don't really want to plug them in and find out - as it is a very nasty noise and I'm concerned about hurting the amp.

Any other ideas?
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#2
i would do the eraser check. simple, with amp on, lightly tap on the tubes.and if you hear one make loud nosies or chattering, you have got a microphonic tube. that could potentially be the easy answer.

good job on giving the detail in the first post. that makes us third shifters' happy.
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#3
^^Should I tap on every tube, including all the preamp tubes?
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Pestilential Flood
#4
Errrr, is that not a bit dodgy sticking your fingers into the back on a live amplifier?
You might find that not just the tubes will be glowing!
#5
I think he meant to use the eraser end of a pencil, not my bare fingers.


Also, does anybody think it could be one of my cables gone bad? I don't know why that would cause this problem, but it is working quite normally now that I've stopped using those cables. One of them is a very cheap cable...
Atmospheric dark metal w/ black and death metal influences:
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Pestilential Flood
#7
Quote by mt-ed
Errrr, is that not a bit dodgy sticking your fingers into the back on a live amplifier?
You might find that not just the tubes will be glowing!


if you licked your fingers and messed around the tube sockets, or are probing in the chassis with your fingers (inside the guts, not outside), then there is a probability of a zap.
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Quote by andersondb7
alright "king of the guitar forum"


Quote by trashedlostfdup
nope i am "GOD of the guitar forum" i think that fits me better.


Quote by andersondb7
youre just being a jerk man.



****** NEW NEW NEW!
2017-07-07 2017-07-07 Update and a Chat On Noise Constraints *** NEW FRIDAY 7/7
2017-04-13 RUN AWAY from COMPUTERS!!! TCE? RANT ALERT!!!
2017-03-02 - Guitar Philosophy 1001- Be Prepared For the Situation (Thursday 2017-03-02)
2017-02-21 How to Hot-Rod the Hell of your Stratocaster for $50! (Tuesday 2017-2-21)
Resentments and Rambling from a Guitar Junkie
---> http://trashedengineering.blogspot.com/
#8
If it doesn't do it with just guitar into amp and no effects it won't be the tubes.
You are on the right path. Keep changing things one at a time until the fault recurs. My guess is that one of your pedals is broken and oscillating.
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#9
Quote by Cathbard
If it doesn't do it with just guitar into amp and no effects it won't be the tubes.
You are on the right path. Keep changing things one at a time until the fault recurs. My guess is that one of your pedals is broken and oscillating.


Well, I only have one pedal, and it's working. So the only thing left is the two cables I was using.

I guess I'll re-attach them one at a time to determine which one is the culprit. Thanks for all the help guys!
Atmospheric dark metal w/ black and death metal influences:
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Pestilential Flood
#10
Update: Now I'm a little perplexed. I've got everything setup the way it was when it was squealing, played for 1/2 an hour, and everything worked perfectly.

Do microphonic tubes go "in and out" of function?

I guess I won't worry about it unless it does it again...
Atmospheric dark metal w/ black and death metal influences:
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Pestilential Flood
#11
Quote by KailM
Update: Now I'm a little perplexed. I've got everything setup the way it was when it was squealing, played for 1/2 an hour, and everything worked perfectly.

Do microphonic tubes go "in and out" of function?

I guess I won't worry about it unless it does it again...


It may of just been a fluke, sometimes it can happen with perfectly functioning gear, in perfect situations for that to occur. If you can't replicate it again, then I wouldn't worry about it, until it happens again, then while it is happening, start testing everything without turning the amp off.
#12
Well, I went about two weeks without a problem, then yesterday the amp squealed again. And it happened right when I stepped on the reverb pedal, and then wouldn't go away as long as the pedal was hooked into the chain.

I unplugged the effects loop and pedal, sound went away. Used different cables with the pedal, sound persisted.

So I'm 99% sure it's the Hall of Fame pedal causing this. But then, after a few rounds of checking different configurations, everything worked again - pedal and all.

Now, the Hall of Fame pedal has the option of true bypass and a buffered bypass. I have it selected for buffered bypass, because that allows me to kick the pedal off and the reverb effect trails off while I play, vs. bypassed, it kills the effect instantly.

But now I'm wondering if the problem lies in the buffered bypass section of the circuitry. (I'm a complete noob when if comes to circuitry and electronics.) The wierd thing is that the problem apparently comes and goes, and right now everything works great.

I suppose I'll have to call TC Electronics, but I'd like to try to understand what's happening first...
Atmospheric dark metal w/ black and death metal influences:
(My Soundcloud page):

Pestilential Flood