• Not As Easy As I Once Thought!

    Keri Szafir • 02/11/2024 at 15:29 • 0 comments

    A story of developing this mod...

    I was asked to do a latch mod on a Boss pedal, a thing people already did in a different way: by using a latching footswitch, either added to the pedal itself or external. Both ways required drilling of the pedal's enclosure - which would mean it can't be restored to the original condition should it magically reach the Super-Duper-Unobtainium-Mojo-Vintage-Cult-Following-Yadda-Yadda status bringing up hundreds or thousands on Reverb. Not really a thing with mass-produced pedals, but still, thinking a few decades down the line. So, I decided the mod has to be 1) reversible, 2) invisible. At first I tried using a latching reed switch and a magnet, but this proved problematic as the reed switch needs different magnet orientations for the on and off action. Seeing this ain't gonna work, I went for electronic solution.

    I did some research for latching switches and finally found a circuit based on two NAND gates forming a RS trigger, with RC circuits on the inputs, with different time constants for resetting and setting. I tried that with a 74HC00 (HC because I was dealing with 3.3V on VCC), got it to work, then went through a bunch of "what ifs"... like, can I build it with discrete transistors and diodes? This turned out utterly simple on a breadboard, and it worked after a bunch of tweaks, so I brought on my friend's Protel 99SE (call me old school! I was going to use it to learn the basics of Altium Designer, and it turned out the other way, with learning AD first and then Protel). I designed and etched a little PCB with surface mount parts, soldered it and it didn't want to work... Stray capacitances? EMI? Different part parameters? Not sure, but I modified the circuit some more to get it going and it works nicely now.