bandmaster problem

[jezzbo]

Hi all, Today I played my 1966 Bandmaster(AB763)
When playing with the volume at 6 the amp first sounds fine and then begins to make a lot of (non musical) loud noise. (when te amp is a few minutes on)
This is when I hit a chord (like first position E).
The amp hums and makes loud noise and distorts. I can not hear the chord I'm hitting.

What could this be?

Thank yo for helping me out.

[Reeltarded]

Is it the vibrations or the heat? When you tap it with your fist does it change the noise?

[jezzbo]

Strange, now It seems fine. (when playing)
When I tap the amp with my fist, I do hear noise.

thanks

[martin manning]

I think Reeltard is suggesting a tube failure. You could try tapping each tube individually with something like a chopstick.

[jezzbo]

I will try this. Thanks

[Reeltarded]

Well, yes and no, but probably.

When a single power tube loses bias the amp will hum loudly. There was the chance that some corrosion at a chassis ground is the cause too. Depends on what noise it's making with the hum.

Since you say it's working ok again get in there with some tube cleaner and get the power sockets clean. The hum could easily be corrosion/oxidation in the sockets too.

If it does it again watch the power tubes. The one that is darkest is the trouble side and the other gets a bright blue halo from the sub and ultrasonic signal. Easy find.

[jezzbo]

Ok, thanks. I'm gonna try again tommorrow. (a bit to late to annoy the neighbors)

[vibratoking]

It's never too late to annoy the neighbors.

[Reeltarded]

More likely a perfect time.. RIGHT NOW!

1! 2! 3! Anda...

[Firestorm]

Clean the pots, clean the sockets, clean the jacks. Contact cleaner for jacks and sockets, pot cleaner for pots (CaiLube or whatever it's called now). Electrolytic caps original? Tubes good?

No point annoying the neighbors unless it sounds awesome.

[Structo]

+1
Check the easy things first.

Has the amp been serviced lately?

Tubes should always be the first suspect unless something else is obvious.

[jezzbo]

Ok I just cleaned the jacks, sockets and pots.
I also installed a 0.01uF cap from the 10M resistor in the tremolo to ground to get rid of the tremolo ticking. The ticking is not completely gone, but it's better.

It seems that the amp behaves normally now.
(I hope it stays that way.)

Thank you for helping.