A very bad thing has happened....

[Christopher_List at Sonymusic.Com]

Couple of you were curious about what happened with my big power supply
blow ups, so here's the update....

As I mentioned, I blew up two Intl. Power PS's Thursday night., These are
bi-polar adjustable supplies using 723 regulators and MN3055 power trannys.

Turns out that by mixing and matching regulators and trannys from the two
supplies, I was able to get one of them working, then, when I received my
replacement parts Saturday, I got the second working, so not a lot of $$
lost there. While taking apart the PS's, putting them together and testing
them, I learned a lot and learned why they'd been fried. Seems it wasn't
overloading or connection to faulty circuits that blew either one - just my
ignorance! It's amazing that in the two years since I got the first of
these two supplies, I never realized that the MN3055's, that are mounted on
the OUTSIDE of the case, use thier casings for one of their contacts (the
collector? - I forget) - yes, yes, this is where you can all groan, because
you know what's coming... So, it never mentions anywhere in the fact-sheet
for the supplies; "beware: the metal trannys on the outside of this PS are
at +26 and -15v!"... I've never worked with these sort of two pin + case
trannys before, so I didn't know.

<Lighting his pipe, Chris reconstructs the scene of the crime...>
I presume the PS that was inside the case made contact with the foil that I
use for shielding the wooden case and got fried. Then, after taking the
synth apart, I laid the other PS upside down on top of the same foil sheet
to test one of the synth modules, turned it on, and the other PS got fried!
The light of this realization started to shine even before I was done
testing the fixed PS's solo, so I wasn't too worried about hooking 'em up
to the synth and giving it a try - sure enough, I hooked it up and the PS
was fine - no need to cut traces or find shorts on the PCB....

Well, of the synth modules, the only thing that got fried were the filters
of the two ASM-1 modules, the trannys and a 3140 bought it. Everything else
seems OK. All in all, not so major of a disaster, and it was good to learn
about how carefully I need to mount these PS's now rather than during a
live show! - OTOH, it was very high stress!

- Thanks for all your advice,
Chris