Noisy tone when playing with big volume

[Leevi]

I'm wondering a very loud noisy tone which appears now and then when playing
with a big volume. The sound scrambles. I think the reason could be a bad contact somewhere?
Do you think a bad tube could cause that? It has something to do with vibration in the cabinet since
it disappears when I connect the amp to an external speaker.
/Leevi

[bluesbear]

Could be a bad tube; could be a cold solder joint or a resistor or cap with a lead that's loose at it's body. The easiest first step would be to replace all the tubes with new (or known good) ones and see what happens. If that doesn't work (or if, like me, affording new tubes isn't so easy), you could try running the amp with the chassis out of the cabinet. Push around on all the components with a wooden chopstick. If you find the bad joint (or component), the amp will let you know!
Be careful with those fingers!!!!
Dave

[stingray_65]

It has something to do with vibration in the cabinet since
it disappears when I connect the amp to an external speaker.
/Leevi

Speaker good?
 can you run a different amp into  the speaker in the cab?
may be at higher volumes the Voice Coil is heating and rubbing.
or is it intermittent?

I've had on more than 1 occasion had to re-tension and clean the  power tube  socket pins. they had all been on combo amps with the tubes mounted upside down.

Ray

[Leevi]

Thanks for the replies guys.
I thought to try with a new speaker but it must be installed in the cabinet in order
to keep the conditions equal. The current speaker is Eminence Red Fang, which is quite new.
Tubes are installed up side down.
/Leevi

[StevieRayVehkakoski]

I've had 2 Red Fangs with horrible cone-cry but that only happens with loud volumes and when bending the ligth E-string on 12th fret or above.

Also I've had a few 12AX7:s and 12AY7:s that sounded like broken glass riding on top of the guitar note with higher volumes or vibration.