"loud Noises!"

[Witek]

My blackface fender tremolux head suddenly started to make a good amount of noise when I play through it. I'm playing my amp and then suddenly it starts to make a loud screeching noise. I noticed that it happens to whichever channel I'm plugged into and that it sounds like it oscillates faster when I turn the volume up (even though the sound itself doesn't get any louder as I turn up the volume. And it doesn't go away when I turn the volume down)

I also noticed that when I play notes this noise happens, it doesn't randomly happen out of silence (it starts as soon as some sound goes into the amp.)

Could this have something to do with the tremolo? (it sounds like tapping whenever the oscillation occurs (tap tap tap tap tap))
I also suspect this has something to do with microphonics, I tapped each tube with a pen to see if they respond to it but I didn't hear anything.

[Blue Strat]

Is this that same amp that was heavilly modded when you got it? Has it EVER behaved itself or is this an ongoing saga?

Do any of the controls on the amp affect the noise? Does unplugging your guitar cable from the input of the amp stop it?

[Witek]

Yes this was the heavily modded amp from before, but that mod has since been reversed and the amp is now back to stock. The amp worked fine for a week or two (have only been playing it that long because it just got new caps).

The noise is not input specific and it happens even when the guitar is unplugged, sometimes. Sometimes it only happens when there is signal going through to the amp (squealing only when there is noise going through), sometimes it's like a feedback noise that occurs when the amp gets noise.

I'll go and get more dynamics of the noise to see if I can play around with it at all.

[Witek]

Oh and since the amp got back the popping noise from the tremolo effect has been getting louder and louder every time.

[Blue Strat]

Clean all tube pins and sockets. Try lightly rocking the tubes in the sockets with the amp on. Any that produce unusually loud noises probably have dirty, intermittent, contacts that must be clean. Could also be a socket that needs to be replaced.

[Witek]

I tried moving around the tubes a bit when the amp was switched on and one of the power tubes made a bit of popping when I moved it around (it sounded like it cut out a bit)

Then when I switched the amp off with the amp not on standby, the buzzing started to go crazy in pitch changes (it kind-of sounded like alien talking actually)



It's turned into a low buzz now that sounds like a crappy motor running, you can still play through the amp, but it covers the guitar signal in a sort of junky mess.

And it appears that if I turn up the vibrato channel with the guitar not hooked up to it it still amplifies the guitar volume? (Guitar in normal channel, nothing plugged into vibrato)

[Witek]

Also, the noise stops when I put the amp into standby, then it's silent when I click standby off until I put a bit of noise into the amp again.

And it seems to have a noise limit too, by that I mean I can play really quiet and nothing will happen through the amp, but as I cross a volume level this oscillation occurs.

[Witek]

Nobody have any input or suggestions?

[Witek]

So after swapping the two power tubes the sound only happens when I play now, a bit better but it doesn't fix my problem.
I found that I can see a blue glow at the top of the tube (right where the connectors touch the whole assembly inside on the bottom plate) when I put noise through the amp.

Could this be a sort of bias issue? I just had the amp biased two weeks ago professionally.

[Blue Strat]

Have you cleaned the pins and sockets yet?

[Witek]

Have you cleaned the pins and sockets yet?

I'm not entirely sure how to do so, I've wiped down the pins with a wet cloth. Do I need to use some sort of solvent?

[Blue Strat]

Wet with water? Not a great idea.

You need contact cleaner. Read the FAQ on my website under Resources.

[Witek]

Did what you said, and the noise is still there. What's next on the checklist?

[Witek]

Ok ok, my bad, I did try changing tubes, but I only had one spare for each power tube, and I guess I mixed up the bad one and put it in for both tries. Yeah it was a bad power tube. Bastard cost me $25 :(

Now, should I get a new set of matched tubes? Right now I'm running a JJ Tesla and Peavey 6L6GC's.
And damn, I just had this thing biased.