[sdiy] A request for info on a '93 Fatar keybed with aftertouch

[John Pallister]

Hello list,

I have recently bought a used Doepfer LMK3+ MIDI controller keyboard sans MIDI
controller, which is to say, I have a nice 1993-vintage Fatar 88-key weighted
keybed with aftertouch. (I have put some photos and notes up on my website at
http://johnp.net/lmk3+/, if anyone would like more detail.) So I need to build a
MIDI interface for it. (I have an Xpander, a Super Bass Station and a FatMan to
be controlled, if that gives this post any much-needed "synth cred".)

I'm trying to start by finding some specs for the keybed interface itself (a
40-pin IDC connector and two plugs for the aftertouch strips).  Doepfer say they
can't help me (so far), and I haven't had much luck yet contacting anyone at
Fatar, either. It looks like a diode matrix with "change-over" switches, but
it's hard to confirm this by visual inspection without disassembling the keybed,
which I'm loath to attempt. I daresay that a trial-and-error approach might
yield some clues to the connector pinout, but I haven't tackled this yet.

The only useful-looking products I've found on the Web are the FMI-MK3 from
Forte Music (http://www.fortemusic.net/mk3.html, page dated 1998, no reply to
emails) and the KV64 FPGA from Hinton Instruments
(http://www.hinton-instruments.co.uk/components.html#kv64, email enquiry sent
moments ago).

I would be very grateful if anyone could provide any electrical information on
my keybed, and particularly the aftertouch sensors, which I believe are some
sort of piezoelectric element, but otherwise know nothing about. However I'm
sure there must be some sort of "standard" circuit for driving them.

Cheers,

John :^P
--
John Pallister
john at synchromesh.com