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Finally got my sIII head finshed today.

Normal channel worked fine, TMB was lots of noise. After some troubleshooting, found that the silver mica 500pf cap was bad. Rats. Put in a ceramic disc cap that I had and tested: noise gone.

Had head standing on end testing with guitar and then no sound at all on TMB channel. Troubleshooting with a scope found that the volume control input was shorted to ground. Had to remove and tear apart control, then all was well.

Now: TMB channel seems a little thin, treble when turned up all the way, amp will start to sqeaul a little. Middle seems to have no effect, bass maybe a little.

Now for the questions...

Could the 470pf ceramic disc cap be causing the squealing?

Anything I should look for?

Gotta go shop...

Thanks

JEM, The ceramic cap would not cause a problem like that.
Considering the effect of the controls is minimal, I'd check the parts & wiring around V2. Recheck that the pots are in the correct places and trace the wires back to the board. Strange about the faulty parts, that is rare.
Also, reflow the input jack connections onthe TMB channel. Can you post pics so we can look them over?

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

OK, back from shopping...

I didn't have time to menti on, the normal sounds great!

I have went through all of the connections, reflowed etc. The treble pot is microphonic as well. Not too much, but it's there.

I have not pulled the input jacks, but checked everything in place and read same as Normal channel. Trying to do the easy things first. ( read... lazy) Seems OK.

I did not have time to include on the first post, that my idiot self, did not have the ground connected to the TMB volume control on the first fire up. Not sure what ills that may have caused.

I don't really have the means to post pic's yet, but I'll try to scrape some crap I have around and get 'em up.

Thanks

Never seen this. What are the symptoms? Sound like you need some replacement parts.


Just reflow them.


Nothing permanent.

_________________
Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps