140B Vibrato Noise

[theseacowexists]

Anyone ever encounter a thumping or clicking noise from the vibrato on a 140B? The noise starts as a clicking noise, and turns into more of a thump when the pot is at 3/4, which is when the vibrato also kicks in. The one I'm working on has both that won't seem to go away. Amp rebuilt, new preamp transistors, grounded socket added, volume and vibrato pots replaced, vibrato bulb replaced with LED/resistor mod from a Vintage Vibe video. The original incandescent lamp was shot when I got the piano (a lug had snapped off from the base of the bulb). I didn't discover that until after I had rebuilt the amp - then I did the LED/resistor mod. Same thing happened before and after that. The only thing that seems to kinda work is grounding lug 3 of the vibrato pot, but that only stops the noise when the pot is fully off.

VV video: https://www.youtube.com/watch?v=SKYInz0le5Y&t=191s

[theseacowexists]

I removed all the wiring for the phono input and the external speaker, and that got rid of the clicking and thumping, and lowered the overall noise floor! Not like we were going to use jacks those anyway.

[DocWurly]

Good data!!