'Vibe/Resly Tone hybrid build — tremolo question/issue

[pacealot]

Hello all,

I'm nearly finished building a sort of hybrid Resly Tone RT-18/Univibe circuit (audio path is very close to stock Resly; LFO and power sections are from various Vibe permutations, including elements of both Neovibe and Forum Vibe), and though it's sounding amazing, the one area that isn't up to snuff is the Resly's tremolo mode. The trem is very weak at best, and disappears completely once the speed goes above around 2/3rds of the way up. I can assume safely that it's not the LFO as such, because the chorus and vibrato modes are just fine at all speeds and the lamp oscillates flawlessly, but I'm not quite understanding the circuit topography well enough to know where else to debug and/or tweak components. I have futzed with the value of the 1µF cap that goes from Q4 emitter to the switch, but to no effect.  I know the stock Resly trem isn't incredibly deep even at maximum intensity, but I did hope it would be slightly more usable than this. Does anyone have any suggestions as to where to start debugging/tweaking? There aren't a lot of extra components, but a point in the right direction might keep me from blundering around changing resistors and caps aimlessly.

The schematic I'm using is this one from guitars-of-love.com (although I did catch an error from Shin-Ei's original published schematic which was propagated here, where the 47K resistor on Q2 collector is given as 4.7K — a whole lot of input clipping was the result before I found the mistake and swapped resistors):

https://www.guitars-of-love.com/images/gol_repairs/resly_tone_RT-18/Reslytone_RT-18_original_schmt.pdf

I can read and post voltages and/or additional info a bit later on if it might help shed any light on the subject...

[Kipper4]

The light might just be contributing to the issue.
Take this with a pinch of salt since I've never used a ,lamp, only Leds.
When the lfo gets to a certain speed the ldr might not be able to detect fast enough to see the differences in brightness and might diminish the perceived effect.
Rich

[pacealot]

Thanks, Rich — I thought possibly so too, except that the LDRs are responding just dandily in chorus and vibrato modes, even at top speed (and it gets nice and fast without losing intensity).  I'm beginning to suspect a possible breadboard intermittence, or simply that I've hooked it up wrong, even though I feel like I've checked it a thousand times (it's always the thousand-and-first time that you finally catch the mistake, isn't it?).  Well, back to the drawing (bread)board, as it were...

[pacealot]

Almost a year later, I wanted to self-necrobump to share that the resolution was that, indeed, the schematic above had another error in it in the connection of the tremolo components, and that was the issue (I had actually "corrected" it, which is what caused the trem to go from briefly working to not really at all). So bear in mind that, in that schematic, there are at least three known errors in it at this point! Better to use one of the PCB traces of the RT-18 which are out there and appear to be accurate (or else stick with the known-good Univibe schemos)....

[Nasse]

Had old tremolo circuit some 40 50 years ago with lightbulb and that was with lightbulb and there was small DC fed from parallel pot resistor just before started to light to smooth bulb action



Small lightbulbs have disappeared. Every shop had flaslight of bicycle lamps

[pacealot]

Luckily both Mouser and Small Bear still stock the #7371 bulb, which works great in this circuit. LDRs, on the other hand, are a whole 'nuther issue — ugh....