ODS troubles when cranked

[Jelle]

Hi,

I hope you guys can help me with this one...
I have recently build an ODS reverb combo that is sounding real nice. However, when the master volume is up and a bass note is played hard, the amp starts making a loud noise like the mechanical vibrations from the speaker are causing troubles in the amp. This is a very unmusical sound/oscillation that goes away when the master is turned down.

The amp works flawless when outside the combo or played into a separate cab. Also the three switches on the front are popping. Wiring looks ok and the other amp that I build does not pop. I have opened the amp to search with chopsticks and the critical areas are:
1) the ground buss (!)
2) the preamp board
3) The input grid coax of V1a
4) the reverb transformer wires
Kinda all over the amp... but mainly the ground buss near the V1a input grid.

Replacing the tubes does not solve the problem.

Any suggestions? Cannot post pics right now...

Thanks,

Jelle

[Don Symes]

Well, I'd probably start by revisiting the solder joints on both ends of each of the connections you mention.

Then I might try isolating the tube sockets from the chassis with grommets or something (hi-temp surgical tubing?) (tedweber.com has a shock-mount for 9-pin sockets for $6)

Since your other unit doesn't do this, though, put 'em side by side and closely compare everything before you put in a lot of dough.

[Jelle]

Don,

Thanks for the reply!

The problem turned out to be a cold solder joint from the ground buss to the chassis. Problem solved! :-)

Jelle