Rehousing Dod flanger, footswitch troubles

Started by Flammysnake, January 31, 2017, 01:32:51 PM

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Flammysnake

New here but have read and learned a lot. For that I thank you all.

I've done some lightweight modding/circuit bending a Dod GFX75. It's a stereo flanger. It does not however fit into the pedal anymore so I've decided to rehouse it, which is fine, except for the footswitch. I've got some soldering skills, but my schematic reading abilities are extremely sad and I just can't wrap my head around what I'm looking at, so I figured simpler is better and I'm trying to attempt to add a new footswitch but I'm not sure I can easily add a simple 2P2T switch onto this stupid thing to make it turn on and off. I thought it would be easier than a true bypass and I don't need anything fancy, but now I'm not even sure how I would wire either one to the pedal. I'd rather not even have the stereo output, but at this point I'd deal with it just to be able to add the footswitch and gain some understanding of what I did. Can anyone point me in the right direction or tell me what the hell I'm doing, or should do?

Thanks in advance!

reddesert

The DOD FX pedals use a momentary contact SPST footswitch that triggers a flip-flop (CD4007 chip in the schematic) to go low or high, which triggers a JFET (it's Q5, J113 in the FX75 schematic I'm looking at) to conduct, either allowing or denying the effected signal to pass the JFET and get to the outputs.

The footswitch and LED are on a separate little PCB, so you could get a regular momentary switch that mounts in your new enclosure and wire that to the little PCB in place of the original switch.

Or you can wire it for true bypass with a DPDT or 3PDT latching switch, but then you need to read the schematic to understand which parts to circumvent/discard and where to get the signal to/from the switch.

Flammysnake

I feel like this sounds silly to ask, but I like to clarify. In wiring a new switch to the pcb where the old switch was, I should of course remove the old switch? I had tried removing it but for the life of me I couldn't get it to remove, but perhaps I need to just try harder.

reddesert

Since it's a normally-open momentary switch (I think), having the old switch in there shouldn't hurt; you could just wire a separate switch in parallel with it. I don't know exactly what it takes to get that switch off, but it's a pretty common repair. You probably need to desolder the contacts, then heat each contact up a little to melt any residual solder while prying it up with a pick.