[sdiy] ASM1 VCO

[Oren B. Leavitt]

Some suggestions:

Since the 3140 is so easily fried if miswired, use a TL071 (or other bulletproof
op-amp with a high input impedance) in place of the 3140s to get the VCO
initially working. Once the VCO is working, swap in the 3140s (making sure
you're well grounded against ESD - MOSFET input) and do your fine-tuning and
calibration.

On your PCB, make sure that is no blackened rosin or other burnt debris between
or near the solder pads. Check also for cold joints - connections that didn't
get enough heat.

Physically stressed components can be another cause. Check for hairline cracks
on resistors, etc.

Make sure your test leads are good, too.
I've spent over an hour one time trying to figure out why a circuit was behaving
weirdly.
It turned out that a banana plug on a cable connecting the ground (0V) terminal
of a +/-15V power supply to my circuit was intermittent. I replaced the cable
and all was fine.

Chris Crosskey wrote:

> 3140's fried ......any takers for the rest of it?
>
> chrisc
>
> > -----Original Message-----
> > From: Josh Randall [mailto:jorandal at vt.edu]
> > Sent: 12 April 2002 15:28
> > To: synth-diy at dropmix.xs4all.nl
> > Subject: [sdiy] ASM1 VCO
> >
> >
> > I've made progress on my VCO but not in the right direction :(
> > I wrote recently because I was getting funny shaped waves.
> > Now all I am
> > getting is a large negative voltage.( but as far as I know I havn't
> > changed anything.)  I have checked to make sure it is gettin power
> > corectly and also looked for shorts.  I don't see anything
> > that stands out
> > although some of the solder pads are a little close.
> >
> > What else should I do?  I have very limited experience at this.
> >
> > Thanks for the help.
> >
> > Sincerly,
> >
> > Josh Randall
> >
>
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--
Oren Leavitt
oleavitt at ix.netcom.com