AB763 HELP!!

[Karl]

Few days ago my amp AB763 started making popping and crackling noises when I had been playing it for a while, this noise stopped after a while and then came back and went away and so on.
But now few minutes ago I was playing the amp and I added some pedals and on the first note I played the amp went crazy and started making loud helicopter like sound and I turned it off unplugged my guitar from the input and waited for a while and turned it on again and it still made the same helicopter like sound. I tried to turn it on one more time and now it is squeeling loudly.

What have I done??? Any ideas?

[Karl]

I fixed the helicopter sound but the crackling and popping is still there.

Any ideas ?

[Phil_S]

Could be a variety of stuff. Pick the low fruit first. If you have spare tubes, it is time to put them in. Mark the old ones with a Sharpie so you know where they were.

When was the last cap job on this amp?

[Structo]

The four C's. lol

Change tubes.
Corroded/ oxidized socket pins.
Clean and re-tension those.
Check the caps.

[txbluesboy]

Okay, while we're talking AB763, I pulled my Super Reverb out to play with it and noticed it makes a crackling noise when you turn the standby switch on and off. It sounds marvelous when playing it, it only makes this sound when going in and out of standby. Should I replace all the filter caps, or do you think it might be a funky resistor somewhere?

[Karl]

Okay, while we're talking AB763, I pulled my Super Reverb out to play with it and noticed it makes a crackling noise when you turn the standby switch on and off. It sounds marvelous when playing it, it only makes this sound when going in and out of standby. Should I replace all the filter caps, or do you think it might be a funky resistor somewhere?

Try a cap over the standby switch like on the ODS.

[Ron Worley]

Sometimes it the switch itself that is the issue- the contacts get funky with age. Try swapping it out with a good new Carling SPST.... may do the trick....

Ron

[skyboltone]

Sometimes it the switch itself that is the issue- the contacts get funky with age. Try swapping it out with a good new Carling SPST.... may do the trick....

Ron

And if you want to be really slick use a dpst and parallel the contacts for twice the voltage handleing!

[txbluesboy]

I couldn't find an example of a Dumble with a cap across the standby switch, but assumed maybe you were talking about the cap across the OD and Mid boost switches. I tried a .1uf cap across the switch but it didn't help. I'll try replacing the switch next, but I dont think its the switch at fault. The sound is sort of a crackle-whooosh when you turn it on and maybe a wooosh-crackle when you turn it off ( Hey- Im serious now-stop laughing !! ) It really sounds to me like a cap charging and discharging. Thanks for your ideas so far---any more thoughts?

[b24warbaby]

I couldn't find an example of a Dumble with a cap across the standby switch, but assumed maybe you were talking about the cap across the OD and Mid boost switches. I tried a .1uf cap across the switch but it didn't help. I'll try replacing the switch next, but I dont think its the switch at fault. The sound is sort of a crackle-whooosh when you turn it on and maybe a wooosh-crackle when you turn it off ( Hey- Im serious now-stop laughing !! ) It really sounds to me like a cap charging and discharging. Thanks for your ideas so far---any more thoughts?

Aren't those .01 called death caps ?

[txbluesboy]

I fixed the problem I was having by installing a grounded plug and disconnecting the ground switch. Thanks