A very bad thing has happened....

[Gene & Debby Stopp]

Bummer, man, bummer. Hate it when that happens!

Have you made any progress yet? Any updates?

If I were to speculate on what happened, I'd guess that the original power
supply blew up (due to excessive loading, perhaps?) and took something with
it on one or more of your attached modules. When you attached the next
power supply, the blown-up module then took that out too.

However, I would think that the next power supply would over-current
shutdown when attached to the faulty circuit, rather than blowing up as
well! Especially a commercial 3-amp unit. Is the 3-amp supply definitely
hosed? Or did it recover if you removed it from the faulty circuit?

Doing the ohms test on a blown-up PCB may or may not lead you to the
problem - the measurement under a no-power condition may be misleading.

I've not blown up an ASM-1 yet, so I don't really have an idea what blew.
It sounds like you have a problem on the (-) rail, so I'd rule out the
parts on the positive rail (like the CMOS), at least at first. The one part
that blows up nicely is the CA3140 - the only thing is, they blow up if you
static-zorch the FET inputs during non-grounded handling off of the circuit
board, but I'm not sure if they die from power supply problems.

Other parts that cause supply shut-down include the bypass caps to gound on
the supply rails - my Taurus I pedals died that way once, and it was a
bypass cap.

When confronted with a power-shorted PCB, the best way I've found to
proceed is to start cutting the power supply traces on the circuit board.
Use the "divide and conquer" technique - cut the (+) and (-) traces in the
middle of the circuit board, and if the short is on the half that is still
going to the power supply, then the supply will shutdown (or blow up,
apparently!). If the short is on the half of the PCB that is now
disconnected from the supply, then the power supply will be okay and the
short is in the half that's been isolated. Add a solder bridge to the cuts
you just made, and cut in the middle of the offending half, and keep going
until you've found the culprit.

This will make a bit of a mess of your traces - to cut a trace, use a sharp
knife to make two cuts about 1/8" apart, straight across the trace. Then
take the tip of a hot soldering iron and rub it on the little isolated
section - it will get hot and fall off the PCB, leaving a 1/8" gap in the
trace. To re-connect a trace, scrape off about 1/8" of the soldermask on
either side of the break, exposing the tinned trace ends. Then solder a
piece of jumper wire (like a resistor clipping) across the break.

Anyway bummer about your situation, and hope this helps....

- Gene
----------
> From: Christopher_List at Sonymusic.Com
> To: synth-diy at horus.sara.nl
> Subject: A very bad thing has happened....
> Date: Thursday, July 10, 1997 10:03 PM
> 
> SO I was playing with my modular just now, and I knew I was pushing my
> power supply to the limit - it had been getting very hot, and the prior
> night it had locked up - but came back to normal simply by switching
> everything off for a minute then turning it back on. Well tonight it did
it
> again, but it didn't come back.