Help Completing/Debugging old Gnome Kit
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Author:  ericjasonnewman [ Mon Oct 15, 2012 2:07 pm ]
Post subject:  Help Completing/Debugging old Gnome Kit

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!


Author:  PAiA-Scott [ Tue Oct 16, 2012 11:19 am ]
Post subject:  Re: Help Completing/Debugging old Gnome Kit

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)...


Schematics with DC voltage test points:

3740TS.pdf [272.77 KiB]
Downloaded 1030 times

Author:  ericjasonnewman [ Wed Oct 17, 2012 7:52 pm ]
Post subject:  Re: Help Completing/Debugging old Gnome Kit

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

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