little problem with audio on HH revD

[kiwi]

Hi, I'm having some problems with my HH Rev. D. I'm using the VCO-audio option but it seems to be making a high pitch squeal all the time. I cant for the life of me figure out whats wrong.

*The Voltages are OK
*The sample pulses and preamp output seem okay..
*I can adjust threshold R31 so that TP9 is almost 0 V (although it erratically varies by +/- 0.1V), and when I place a screwdriver over the coil TP9 swings around by +/- 3.0V. I guess that means everything is working fine up to that point?

Not sure if these readings are normal but I'll include them
IC7 pin 6 -3.7
IC7 pin 9 -2.9

I'm not the biggest electronics wiz, help much appreciated
Thanks
Patrick

[Carl-NC]

Sounds like you are fine up to TP9. IC7-pin9 should be 0V for the VCO option, install R50 but not Q10 or R49. There are 2 jumper options on IC9, make sure both are installed correctly.

[kiwi]

Thanks very much Carl. That advice was spot on. I'd installed both Q10 and R49 - School boy error! Very hard to diagnose a problem when you've installed an unnecessary part. Anyway working perfectly now. Cheerrs!