No +V going to the chips. The +V bead wasn't soldered properly... how dumb.
LFO still isn't working though. Vari & Mix outputs still spitting out a steady negative voltage, but Pulse & Square now going positive (only)...
Hmmm... onwards.
_g
LFO still isn't working though. Vari & Mix outputs still spitting out a steady negative voltage, but Pulse & Square now going positive (only)...
Hmmm... onwards.
_g
--- In cgs_synth@yahoogroups.com, "Guy" <guy@...> wrote:
>
> --- In cgs_synth@yahoogroups.com, sasami@ wrote:
> >
> > >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.
>
> 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.
> Diodes are fine.
>
> >
> > >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
>
> Hmm, okay, so that's my LFO 2. :-)
>
> >
> > >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.
>
> Thanks for telling me now. I was just about to dismantle half of the wiring...
>
> _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
> > >> >
> > >> >
> > >> >
> > >> >
> > >> >------------------------------------
> > >> >
> > >> >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/>
> > >>
> > >
> > >
> > >
> > >
> > >------------------------------------
> > >
> > >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/>
> >
>