Tremolo intensity control

[shzmm]

I'm about finished on stand-alone tremolo/reverb unit in the schematic below but I still have a question about the intensity control of the tremolo. (As shown it's transistor version of the Fender tremolo by R.G. Keen with an led/ldr combo.)
The problem is that the intensity control really only kicks in at the last 1/4 of the turn. I've tried different value pots, putting resistors in series, etc. but no luck.
Anyone have an idea on what this could be?
Thanks for your help...

[tubeswell]

taper of the intensity pot maybe?? (are you still happy with the depth at pot max, or is the issue one where there just isn't enough depth period?)

or try playing around with some of the .01/1M RC combinations (e.g. try .02/1M in one of the combos) perhaps. Have a look at some of the classic fender trem circuits to see where they vary from straightforward RC values.

[shzmm]

Thanks for the reply. Unfortunately I have tried different tapers lin and log, different values for the pot, etc. It sounds fine it's just there's no fne control of the depth of tremolo. The other values such as capacitors in the oscillator are essentially standard-- .01.
I have the feeling it might have more to do with the vactrol clm6000 but then again I'm not certain.

[GibsonLover]

Isn't the CLM6000 forward biased when it's pulsed on? That only gives you one diode drop of amplitude for intensity, right? I think R.G.'s schematic had the Fender Opto in there, which is a neon with Big voltage across it. A bigger problem - Grounding the drain of the IRF820 does not look functional. Try removing that wire first, and the first comment may take care of itself. I am assuming that there is a missing ground symbol on the very bottom line.

[Mark Hammer]

In view of the resistance of the output level pot on the tremolo channel (250k) the 50k tremolo depth pot strikes me as being much too low a value. I'm thinking it is probably 500k. Also the drawing shows something to the right of the CLM6000 LED side that looks like a pot, with a wiper tied to the wiper of the "50k" pot. I gather that is the LDR side of the CLM6000, which definitely is NOT a pot but simply a single variable resistance.

From looking at the schematic, it would seem that the depth control is essential a bleed resistance to ground (and should be 500k). The LDR side of the CLM6000 is placed in parallel with the leg of that pot between the wiper and ground. As the LDR drops in resistance when the LED lights up, that leg of the pot drops resistance to ground and the signal is attenuated before reaching the output jack via the 250k pot. How much it is attenuated will depend on the amount of resistance on the other side of the 500k/50k pot. If all 500k is on the "other" side, then there is always a 500k path to ground and no attenuation occurs. If all 500k is on the wiper-to-ground side, then fluctuations of the LDR will have a pronounced effect on the attenuation.