[sdiy] Polymoog episode 1

[Debby and Gene Stopp]

Hi List,

As an alternative to the TV show "Survivor", I promised to pass along my
experiences with the busted Polymoogs that I am slowly trying to restore.
Since the first TV episode is currently on in the living room (mainly
because the TV is still on as a result of the Superbowl, not because anyone
in my house actually wants to see it), I think I'll start typing.

Polymoog #1 is still sitting on the workbench, where it's been for about a
week. The cover is off, the keyboard is totally removed, and some of the
circuit boards are being held in a vertical position by miniature bungee
cords (a technique I made up just for this project - I had circuit boards
dangling, one hand free, didn't know what to do next, looked around and saw
some miniature bungees).

The keyboard was the first thing I pulled out - it's a 71-note Pratt&Read
assembly (E to D) of the old style, plastic key caps screwed on to a metal
channel with color-coded tension springs at the back end. Same stuff as on
Minimoogs, old Odysseys, and Prophets. Anyway it was all filled with greasy
fuzz bunnies and other gunk, so all the keys came off and into a dishpan
filled with hot soapy water. The black keys were all scratched up so I
sanded them with 600-grit wet and buffed them with a Dremel and rubbing
compound. I know, sounds like a lot of work, but believe me they needed it.
I do have a box of old Moog keys, and I totally considered using those
instead, except that the Polymoog uses weighted keys. This means that the
front undersides of the white keys, and the whole inside of the black keys,
are filled with lead weights and epoxy. I would much rather sand and buff
the existing keys than re-weight replacement keys.

The keyboard frame has some problems too, which I'm trying to decide about.
A few of the return bumpers have been replaced entirely with some melted
plastic pieces, so the keys really "clack" when played. What I mean here is
that not only are the rubber bumpers gone, but the metal fingers they are
mounted over are snapped off. Somebody replaced them with some kind of hard
plastic doohickeys melted onto the keyboard frame, so they are physically
correct in their position but their action sucks. Idea number one here is to
sacrifice one of the keyboards from my spare inventory and splice in a
section of metal fingers and rubber key bumbers to cover the crummy octave.
Or I can go open up the other Polymoog and see if the keyboard in that is in
good shape - maybe later.

On the electronic side of things, progress is slow. I've found some empty
sockets, at least one of which (according to the schematic) needs a 7401
quad open collector NAND gate. Not a 7400, or even 7403, but a 7401. One of
the chips that got dropped from the databooks early in the history of TTL.
There's a bunch of these used here. Also there's lots of 4007's, and some
low-profile LED's which are missing, and more obscure parts the likes of
which I have yet to discover....

- Gene