Excellent suggestions, all.
If I understand the original post correctly, you are also in the fortunate
position of having one working board.
If you're still no closer to the answer after trying John's suggestions, you
could try a side-by-side comparison of the two boards. You could start at IC1A
and work backward from there, depending on where you get different measurements
between the two boards. An O-scope would indeed be most helpful here, though
sometimes even voltage measurements might tell you something. Also, resistance
measurements with an ohmmeter without power applied to the boards have helped me
in situations like this.
For example, I just finished up a keyboard encoder, everything worked fine except
the octave switch. Looking at the diode gap of a switching diode quickly told me
where the problem was, but not what it was (that took *another* visual
inspection) - an ever so small wisp of solder was bridging two pins of an adder
IC.
BTW, I think I only live a couple of hours from you, Jeff (I'm in Mount Hope,
Kansas). I was born in Manhattan, the son of a K-State graduate and staunch
Wildcats fan.
Good luck and hope you get it working soon!
Best Regards,
Scott Stites
________________________________________________
PeoplePC: It's for people. And it's just smart.
http://www.peoplepc.com
If I understand the original post correctly, you are also in the fortunate
position of having one working board.
If you're still no closer to the answer after trying John's suggestions, you
could try a side-by-side comparison of the two boards. You could start at IC1A
and work backward from there, depending on where you get different measurements
between the two boards. An O-scope would indeed be most helpful here, though
sometimes even voltage measurements might tell you something. Also, resistance
measurements with an ohmmeter without power applied to the boards have helped me
in situations like this.
For example, I just finished up a keyboard encoder, everything worked fine except
the octave switch. Looking at the diode gap of a switching diode quickly told me
where the problem was, but not what it was (that took *another* visual
inspection) - an ever so small wisp of solder was bridging two pins of an adder
IC.
BTW, I think I only live a couple of hours from you, Jeff (I'm in Mount Hope,
Kansas). I was born in Manhattan, the son of a K-State graduate and staunch
Wildcats fan.
Good luck and hope you get it working soon!
Best Regards,
Scott Stites
>On Wed, 29 Jan 2003, "John Loffink" wrote:href="http://mail.peoplepc.com/jump/http://www.cgs.synth.net">http://www.cgs.synth.net</a>/
>
> Suggestions:
>
> 1) Look for open traces or cold solder joints (hazy looking solder).
> 2) Check power and ground going to all 4 chips with PCB powered. Also
> verify 9 volts from the 7809.
> 3) Check the IC socket connections with the ICs inserted and PCB
> unpowered. Do the IC pins really connect to the PCB trace underneath?
> 4) Beyond this, an oscilloscope starts becoming real handy. You could
> try comparing each op amp stage output between the working and
> nonworking modules with your multimeter. Use DC volts mode first, then
> AC mode for a rough computation of whether any pulses are coming out of
> that stage. This might let you narrow it down to the broken section.
>
> I hope this helps.
>
> John Loffink
> jloffink@...
>
> > I have 2 vc dividers. The first I put together worked right off. The
> > second one refuses to respond. That is, when I start on Ken's
> trimming
> > instructions there is no output from HO. I've checked that I'm
> getting
> > the correct voltage into the pcb, I switched the 4024 and 40106 from
> the
> > working divider to the nonworking divider, I've compared the two to
> match
> > up every component (and orientation), and triple-checked soldering
> > connections - no improvement. Any suggestions? Please keep in mind
> that
> > I'm extremely poor at electronics troubleshooting - just using my
> > multimeter correctly gives me a sense of accomplishment :-).
> > Jeff
> >
>
>
>
> See the following URLS for the CGS Modular Synth home page:
> Main: <a
> Secondary: <ahref="http://mail.peoplepc.com/jump/http://otherunicorn.0catch.com/synth">http://otherunicorn.0catch.com/synth</a>/
> To unsubscribe from this group, send an email to:href="http://mail.peoplepc.com/jump/http://docs.yahoo.com/info/terms">http://docs.yahoo.com/info/terms</a>/
> cgs_synth-unsubscribe@yahoogroups.com
>
>
>
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________________________________________________
PeoplePC: It's for people. And it's just smart.
http://www.peoplepc.com