Electrovibe Issue at Max Speed; Bulb Stalls and Stays Always On (photos and video)

I finally got around to building my Electrovibe and it sounds so good. Only issue I'm having is when I increase the speed knosb (happens on both knobs), the bulb will pulse faster then once maxed, the bulb will remain always on. I have tweaked both trim pots across the full range to see if that was affecting it, but no avail.

Below are some photos and a link to a video. Let me know if more photos or details or needed.

A few things to note - I socketed a few resistors (R4, R12, R14, R15, to experiment with Big Monk's modifications (https://forum.pedalpcb.com/threads/electrovibe-modifications-thread.8703/). At the moment the only resistor that isn't per specs/manual is R12 for the Extended Range at Slow Speeds mod (manual calls for 2.2 M Ohm; I have a 10M Ohm resistor in it). The other 3 socketed resistors are as per specs.

Bulb is VCC 7371 (https://www.mouser.com/ProductDetail/VCC/7371?qs=N8%2Bk0S5zvCYBBpiHgR%2B78A==)
Photocells are NSL-7532 (https://smallbear-electronics.mybigcommerce.com/photocell-silonex-advanced-photonix-nsl-7532/)

Thanks!

Video Link - https://www.veed.io/view/e3b4fc93-cb34-4c68-b5bc-2d0ea8350c81

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Chuck D. Bones

Circuit Wizard
Have you tried adjusting the Gain & Bias trimmers at max speed? Looks like the bulb brightness is too high, although the camera can be deceiving. LDRs are very sensitive and you don't need to run the bulb anywhere near full brightness.

I don't know how familiar you are with the inner workings of a bulb-driven Vibe. Incandescent bulbs have a slow response and at full speed the filament may not have enough time to completely cool off before the next cycle. Try running the bulb at lower brightness and see if that cures it.

Regarding the stomp switches, be sure to put the white washers on the outside when do the final assembly. They look good and protect the paint.
 
Have you tried adjusting the Gain & Bias trimmers at max speed? Looks like the bulb brightness is too high, although the camera can be deceiving. LDRs are very sensitive and you don't need to run the bulb anywhere near full brightness.

I don't know how familiar you are with the inner workings of a bulb-driven Vibe. Incandescent bulbs have a slow response and at full speed the filament may not have enough time to completely cool off before the next cycle. Try running the bulb at lower brightness and see if that cures it.

Regarding the stomp switches, be sure to put the white washers on the outside when do the final assembly. They look good and protect the paint.

I have tried adjusting the Gain and Bias trim pots across their full ranges but the bulb still stays on at max speed. Thanks for the info on LDR's, I am very unfamiliar with them so that's great to know - I will definitely make that adjustment regardless.

And thank you for the washer tip, definitely going to follow that! As I said, the bulb only does that when the pot is maxed out 100%, and I really only plan on using the vibe for the slow swirl sounds so it's not a huge deal. Was just wondering if there's something obvious that I'm missing.

Thanks again!
 
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