After finishing build, sawtooth generator no longer works

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secretL
 
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Joined: Thu Apr 28, 2016 2:55 pm

After finishing build, sawtooth generator no longer works

Post by secretL »

HI,

This is the willzyx kit btw.

Up until building the sequencer section, I had tested everything and it worked perfectly. After the sequencer section I no longer have a sawtooth at R105. The dc Bias with a 3v control signal at R90 is only 6.4v on my scope (when attempting to measure the sawtooth on R105).

Before hooking up J4 to the main board I get 12v 0v 5.33v but after I hook it up and measure IC9 pin 16 to pin 8 I get over 16v (that slowly descends). IC9 pin 8 to D31 I get over 12v and that slow descends too. Ofcourse this is with all the components in so maybe that measurement isn't valid anymore as in the manual there are no components.

One other thing, in my build manual there is a typo in the VCO section and instead of saying to solder in D31 it says D3, so I had left D31 empty until I got to the sequencer section when I realized that this was a typo. However I was able to complete all the tests in the manual with perfect results. I soldered it in before trying out the sequencer but not sure if that is the issue. I replaced it anyways in case it was a dud but there is no difference. I wonder if this being removed has damaged an IC, perhaps the op-amp in IC11? Also when I probe pin 7 on IC11 with the 3v control voltage applied to r90 I get 3v... so thats promising.

Thanks.

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