The first thing you need is a way of seeing what is happening on the various
pins of the ICs. If you don't have a logic probe, run a cord from your VCO
pitch input, connecting a 100k resistor to the tip of the cord (use an
aligator clip), and use the other end of the resistor as your probe. The VCO
and ther module you are trying to fix need to be running on the same PSU or
have their 0V rails connected. The pitch of the oscillator will tell you
what is happening at the pins. Don't think you can use a multimeter instead
- their response is too slow.
Now start at one side of the schematic, and work out what that part is meant
to do. Make sure it is doing it. If not, fix it. When that works, move to
the next bit!
Ken
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
pins of the ICs. If you don't have a logic probe, run a cord from your VCO
pitch input, connecting a 100k resistor to the tip of the cord (use an
aligator clip), and use the other end of the resistor as your probe. The VCO
and ther module you are trying to fix need to be running on the same PSU or
have their 0V rails connected. The pitch of the oscillator will tell you
what is happening at the pins. Don't think you can use a multimeter instead
- their response is too slow.
Now start at one side of the schematic, and work out what that part is meant
to do. Make sure it is doing it. If not, fix it. When that works, move to
the next bit!
Ken
>OK--I've finally replaced the LM358 with a TL072...and I still cant_______________________________________________________________________
>get past stage one--I get leds lit on stage one and the output only.
>I've tried different threshold level settings with the pot. Any help
>is appreciated--I'm just getting started with DIY and (particularly
>new to) troubleshooting. Thanks!
>
Ken Stone sasami@...
Modular Synth PCBs for sale <http://www.cgs.synth.net/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>