CA3130 in ASM-1 VCO?

[Magnus Danielson]

>>>>> "S" == Stopp,Gene  <gene.stopp at telematics.com> writes:

 S> You can't solder a 3130 directly into the ASM-1 PCB, since pin 4 will be
 S> at  -15 rather than ground. Knowing this series of chips (i.e. how easy
 S> they are to blow up), I would predict instant chip death.

 S> However, for those of you with Electronotes, if you go back and look at
 S> the original circuit from which the ASM-1 design was taken, you will see
 S> that the integrator is a CA3130. I forget the exact issue number.

The VCO CA-3140 is only operating in the 0V to 5V range at the output.
The inputs of the CA-3140 is sitting at 0V.

 S> Anyway, when I laid out the ASM-1 circuit board, I decided to use the
 S> 3140 since it's a chip that I wanted to use in other places (like in the
 S> VCF) so I pinned it out for +/- 15v. You could probably doctor up the
 S> ASM-1 PCB to accept a 3130 in the VCO by cutting the -15 trace away from
 S> pin 4 and jumpering the pin to ground with some wire-wrap wire. This
 S> type of re-work is pretty common practice in manufacturing environments
 S> to correct little artwork problems in a new design without having to
 S> invoke the expense (and lead time) of turning a new artwork around. I
 S> don't have a PCB in front of me at the moment, so I'm not sure how the
 S> traces are routed. It could be that the cutting of this trace will sever
 S> the -15 connection to another part of the circuit, so the appropriate
 S> bypass would be needed. But the original design used the 3130, so
 S> there's no reason it shouldn't work once the power pins have the proper
 S> voltages on them.

Pin 3 (positive input) is well tied to ground, cutting the wires to
the pin 4 will not cause trouble otherwhere, so it is just cutting it
and wire the ground over!

But, you can't build the VCF as easy with the CA-3130. They need to
operate on dual power and then you are forced to get the +/- 8V
supplies anyway.

Getting a few CA-3140 seems like a fair deal after all.

Cheers,
Magnus