guest wrote:first off, id like to apologize for that. for some reason i didnt design any reverse voltage protection into the pacemaker board, and i have no idea why, either. so perhaps tossing a few high current shottkey diodes, reverse biased, from the power rails to ground would be a good safety measure for the future. then just your powersupply fuses go, rather than the pcb.
No problem, dude :-) It's my own carelessness at fault, and I'm guessing I'll be more careful in the future. Thank you for the huge amount of time you've put into this project, especially with regards to "tech support". I, for one, certainly don't take it for granted.
first off, are all of the powersupply rails solid? check both the pacemaker and the x0xheart, as they have seperate supplies.
second, is there a strong signal coming out of the VCF out jack? does the filter sweep work as it should? is it triggered by incoming gates, do accent and slide work? does the tune, cutoff, envmod, and resonance work as they should? does the CV change the pitch? both saw and square work?
Everything seems to work fine aside from the VCA output (and maybe glide, but I'm not sure if that even worked before "the incident").
if all of that is good, then check for signal on the volume pot, pin1. if there is signal here, then its the mixer stage. if there isnt signal here, then its either the VCA or envelope generator. turn on accents, and set accent and decay to maximum, and then listen at the VCA output. is there any signal? if not, then its probably the VCA core, and i can walk you through that. are you good with SMT rework? those transistors are tiny.
Volume pot, pin 1 has no signal normally, but does receive the pulse when I turn on accents. And there's VCA output when accents are on! And the volume pot properly attenuates it! So there's progress. What would you recommend I check next? What kinds of readings/signals should I see on J7 and J9? J9 pin 1 reads a constant 5.333v (accent on and off both). J9 pin 3 outputs the signal I hear at VCA out as long as accent is on. Otherwise there's no signal.
Here's a scope screencap. Yellow is J7, pin 1, and blue is VCF out.