--- In cgs_synth@yahoogroups.com, sasami@... wrote:
Diodes are fine.
_g
>Ah yes, I should start there. It's outputting only negative voltages, so that makes sense... Lemme look up the 074 datasheet and find out where to measure.
> >Okay, so it's probably not those. I'm quite certain the speed & shape pots
> are wired correctly.
>
> Something is preventing them from oscillating. Whatever it is, that is what
> you need to find. Make sure your 1N4148 diodes are in the right direction.
> Also make sure that both power rails are getting to the chips.
Diodes are fine.
>Hmm, okay, so that's my LFO 2. :-)
> >But I'm wondering, which part of the PCB is LFO1 and which is LFO2 ? Not
> sure if that matters, but it's most likely that I've done the swap/join
> switches not correctly. I've hooked up the top LFO's VARI pot pads ("top"
> when Power pads are at the bottom) to the swap switch, and so on... Dunno if
> this could influence the oscillation ?
>
> Either can be LFO1 - depends on how you wire them. Usually I would consider
> the one nearer the power connector to be LFO 1
>Thanks for telling me now. I was just about to dismantle half of the wiring...
> >Or should I try to skip the switches as a test, and hook up the outputs &
> pots directly ?
>
> The switches and vari pots are the last of your worries - they don't affect
> the core.
_g
>
> >
> >_g
> >
> >
> >--- In cgs_synth@yahoogroups.com, sasami@ wrote:
> >>
> >> The first step would to be to find out why it is not oscillating, so
> >> investigate the circuit around that area - and that means the speed pot and
> >> the shape pot. Getting two wires to a pot swapped could well kill it.
> >>
> >> Ken
> >>
> >> >...more specifically the Utility LFO, to start with.
> >> >
> >> >Wired it up, with Join/Swap switches. +/-12V feed, banana jacks.
> >> >LEDs don't flash, but a quick DVM measuring at the outputs gives me app.
> >> -4V on most and even -8V on some other outputs (the Vari's, I think). The
> >> output voltages don't seem to fluctuate at all... (I did not do an audio
> >> check, nor do I have a scope)
> >> >
> >> >Apart from the obvious basic legwork (IC's put in correctly, no bad solder
> >> joints, no short circuits at first sight, and that tricky little jumper is
> >> present), what would be the methodology to start hunting for bugs ? Which
> >> points should/could I measure first ? What would be good deductive steps to
> >> undertake to pinpoint the problem ?
> >> >
> >> >
> >> >tia !
> >> >
> >> >_guy
> >> >
> >> >
> >> >
> >> >
> >> >------------------------------------
> >> >
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> >> >
> >> >
> >> >
> >> >
> >> _______________________________________________________________________
> >> Ken Stone sasami@ otherunicorn@
> >> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> >> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
> >>
> >
> >
> >
> >
> >------------------------------------
> >
> >The CGS Modular Synth home page: http://www.cgs.synth.net/
> >Yahoo! Groups Links
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@... otherunicorn@...
> Modular Synth PCBs for sale <http://www.cgs.synth.net/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>