Zombie mod with MN3207 not working

[puretube]

the solder pad for R17 to wiper of speed pot is very close to another track in the layout of the PCB : maybe a little dirt around it causing leakage?

[Mark Hammer]

I'll let Anthonie cover off minimizing distortion since I suspect he has a much better handle on it.  I will mention, though, that a great deal of the range of the LFO rate control tends not to be of much use for most *conventional* chorus effects (I'm overlooking quasi-ring-mod effects here and slow flanger-like sweeps), and you may consider increasing the value of R16, decreasing the value of the speed pot and changing the value of C8 to obtain a speed control that is usable across the entire range and does not squeeze LFO rate changes of most interest into a small arc of rotation.

*Because* of the perhaps broader range of speed than is necessary, speed pot taper can be an issue, and the problem you have may well be related to pot taper.  Maybe not, too, but ponder it and do what works for you.

Do take a look at the Zombie mods noted on Munky's site since that will save you a trudge through the archives here.  Being able to adjust mix is nice, as is the capacity to achieve vibrato, and the ability to move into the flanger range.  Having a clock cap value of 220-270pf (instead of the 1000/500pf choice for "mode") provides for a very nice slow Leslie tone.

BTW, congrats on getting it working, and thanks for lending support for the drive to use bias trimpots.

[bioroids]

I'm gonna go thru this on the weekend, because I got a few tremolos to fix..

I'm using for now a linearB pot, but going to try a logarithmic one. It seems like, as Mark says, there is little usable range on the entire scale, but also the waveform is kind of abrupt, on slow modes sounds like a sawthoot wave. Is this right?

It's funny because is the same defect on the Hash Browns flanger, wich uses the MN3207 as well (coincidence?? i suppose)

Also, when i get to the slowest part of the pot, the effect dissapears, like the oscilattor stopped working, and the slowest speed with audible effect is not so slow. Maybe thats how it's supposed to be.

Well, good luck everyone and thanks for your help. There's always a lot of things to learn, a least for me, about the electronics of the effects, and this is the best place to find that knowledge.

Regards

Miguel