Help Completing/Debugging old Gnome Kit

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ericjasonnewman
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Help Completing/Debugging old Gnome Kit

Post by ericjasonnewman »

Years ago, I had assembled a gnome kit, and almost got it working, when my mom accidentally threw it out... Long story, but I've been pining for one since. I recently got a half completed kit off to EBay, and finished it. It is almost working, but I have a strange problem that has me stumped. The VCO is oscillating at a very high rate, and refuses to slow down to the audio range. So far, all the components and wiring check out, but I had to provide a new IC, which is a good LM3900. I did replace several of the 2.2uf caps, as they seemed noisy, and that didn't fix anything or change the symptom besides reducing noise.

I can see that the Range control seems to be varying the voltage between 0 and over 15 volts. Can someone share some experience about what to look for. I am afraid that if the transistors are bad, I'm gonna have a tough time. Also tried a different 470pf cap, but no change there either.

HELP! The VCA, Noise, VCF are all fine - and I can make wind noises, and gun shots all day long, just no tones!

Thanks!
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PAiA-Scott
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Re: Help Completing/Debugging old Gnome Kit

Post by PAiA-Scott »

Maybe it's Q3 which mounts on the panel with connections to the power switch and it being a different transistor than is shown in the manual (PN2712 vs 2N2712)...

http://www.paia.com/talk/viewtopic.php?f=29&t=200

Schematics with DC voltage test points:
3740TS.pdf
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Scott Lee
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ericjasonnewman
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Joined: Mon Oct 15, 2012 1:45 pm
Hometown: NY
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Re: Help Completing/Debugging old Gnome Kit

Post by ericjasonnewman »

Wow - an awesome tidbit - thanks a lot - I'll recheck all these orientations tomorrow. I sure hope that is it!
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