Tremolo Thump - 64 Deluxe

[Tom Phillips]

...clipped in a 22uf across each 16uf filter cap 1 at a time = no change in noise at all

One thing that comes to mind is the integrity of the grounded side of the filter caps. Might be worth checking the continuity from the negative lead of the screen supply filter cap to ground. (Not just to the eyelet but all the way to the final ground point.

[Valvehead]

One thing that comes to mind is the integrity of the grounded side of the filter caps. Might be worth checking the continuity from the negative lead of the screen supply filter cap to ground. (Not just to the eyelet but all the way to the final ground point.

will check that tonight !

[Valvehead]

All grounds coming from the doghouse check perfect at their destinations.

I did some more Chop-sticking

no change --i am going to talk to the owner tomorrow about letting me put in new filter caps and at least new 6v6. This thing is worth some $$ .

the board in this thing is VERY warped/ wavy. I loosened it up to move the top board up, flex it, chop stick.... no change.

Starting to think Heim is right.....conductive board?

someone posted a good video on how to heat/clean these on youtube.....heat gun / alcohol .....was it Psonic? Brad Webb ? Lots of labor time--but an option .

[Helmholtz]

It might be a good idea to see if all circuit grounding points shown on the schematic (around 20) have a resistance to chassis below 1R.

If it's a conductive board you should be able to see some (pulsating?) DC voltage between eyelets using a high impedance DCV meter.
If so, cleaning around eyelets that connect to V5 and the roach with some isopropyl on a Q-tip (cotton swab) might help.

https://www.youtube.com/watch?v=5OWSUYKZsag

[Tom Phillips]

...i am going to talk to the owner tomorrow about letting me put in new filter caps....

Excellent approach. It can be a crap shot to troubleshoot issues when all the circuitry is running on 59 year old electrolytic caps. It would be interesting to scope the DC rails for the presence of the tremolo low frequency oscillator signal now while the amp is still exhibiting the problem with the original filter caps. The issue could be due to aging of several of the caps. If so, then maybe your test of clipping a new cap across just one at a time was not sufficient to stop the thumping problem. Remember that the job of those caps is not just "filtering" the 120 Hz ripple but also "decoupling" all AC signals form riding the DC rails from one part of the circuitry to another.

...This thing is worth some $$ ...

More like $$$$. Around here they are going for $3,000 to $5,000.

[Valvehead]

Well ... its fixed ! It was the filter caps . Amp hum is way better and 90% of the trem noise is gone....then to get the last ticking out i added the .01 cap at the bug. Trem is perfect now ! THANKS. trying to grab some new 6v6 for it today .

[Helmholtz]

Well ... its fixed ! It was the filter caps . Amp hum is way better and 90% of the trem noise is gone.... .

That's not consistent with your results of post #7. But maybe you cured a bad solder joint when replacing caps.

[Tom Phillips]

That's not consistent with your results of post #7. But maybe you cured a bad solder joint when replacing caps.

We should also consider that although the the issue was not solved when he clipped new filter caps across each old cap one at a time but was solved when he replaced all the filter caps The issue may have been due to the combination of multiple very old worn out filter caps.