Hi,
I'm working on my Guyatone GA-1050 again. It's basically a Fender Twin SF with only two output tubes.
So far, so good. Added a tube rectifier for fun, changed the transformer and got some really nice results with it. Added some shielded cable to reduce the Reverb hum at high settings and added a switch to the Intensity Pot of the Tremolo to disable it. Adds some extra gain, but now I could hear the tremolo ticking. Nothing wild, but after I turned up the speed control to the highest value, it started to go wild....means the ticking now was a plopping and really loud. Did the usual thing and changed the lead dressing, added shielded cables, added the Fender recommendation of a 10n capacitor from the 10M resistor to ground and all made the ticking lower, but not at the really end of the speed setting.
Plopp, Plopp.
OK, the next step was checking voltages and when I touched the Anode of the oscillator, the plopp stopped and everything was dead quiet. And yes, all voltages OK. Only a piece of wire touching the Anode was enough, so no chance to see what was going on even with a 1pF probe of my Scope. I added a few k as grid stopper and that killed the obviously wild oscillation. I'm pretty sure, a few pf from the Anode to wherever would have stooped as well.
Have you ever noticed such behaviour before? I used ceramic NP0 capacitors in the oscillator, as they are really small, low tolerance and I had them sitting here. Normally, I use Orange Drops, but I thought, it's wasted material for the Tremolo
So. anyone had this before? Did not find anything on the net. Good thing now is after all the changes, the amp is dead quiet :-)
Best regards
Karl-Heinz
Topic: Fender style Tremolo going wild (Read 1533 times)