Arp Axxe: 15V offset at VCO sliders?

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Arp Axxe: 15V offset at VCO sliders?

Post by rjd2 » Fri Dec 25, 2009 3:28 pm

hi guys, im hoping something might have some insight on my axxe. i recently stopped getting VCO outputs at the VCA out. the specs:

1- noise passes the VCF fine, and the VCF will self-oscillate.
2-all other functions have been restored to working.
3-on a scope, i actually can see the waveforms all the way up to the VCF input. i just dont HEAR them. i also see noise on scope. but i DO hear noise. wierd.

here's my main culprit: on both of the saw and pulse VCO sliders, there are 3 pins: input from VCO circuit, output to VCF, and a 3rd pin(i'd call it "wiper", but its probably more like CCW or something, dunno how slider pots are laid out). on this 3rd pin, i am getting +15VDC constantly. this 3rd pin of both saw and pulse connects to the BIG pin 6 of the VCF. 15V traces all the way to it.

so, the voltage readings of the VCO(pre-slider) output look like this: about 7V for saw, about 10V for pulse. noise reads about 3V. then, when it hits the slider, there is this 15V "offset". so the V readings AFTER the slider will range from either 7V or 10V to 15V, depending on how far up or down the slider is.

is this normal? i've gone over every other part of the synth, and im at a loss as to where to look at this point. could i be getting some "backtalk" in voltage from the VCF, or is this normal, and my problem really is elsewhere? thanks, rj

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