The S/H (sample-and-hold) Analog Board enables the Bend and Mod wheels
to be interfaced via MIDI. The nice poeple at Korg have actually provided
a lot of the circuitry on the Polysix boards, and only a couple of
hold amplifiers and a VCA need to be added.
The schematics show the electronics on the
board. It is
connected to the Polysix via an 8-pin connector
(to the KLM-367
circuit board), and a single wire to the Bend Range pot (VR3 on the KLM-369
circuit board). No pin numbers for the IC's have been given. Instead,
refer to the pictures below.
...and this is what the wiring on the underside looks like.
The black arrow points to the connection point for the BEND CV output from the board (TL072 pins 1 and 2, connected to the BEND RANGE pot CW terminal).
The trimpot on the board is set up after everything has been mounted, and is set so that there is a reasonable (i.e. same as before the modification was installed) amount of LFO modulation when the mod wheel is fully advanced. Alternatively, it can be replaced, together with the series-connected 22k resistor, with a single 68k resistor.
The board is mounted just to the left of the two main Polysix boards as shown below.
(The strange cable emanating from the EPROM socket on the CPU board is
for my Z80 development system).
Back to my Polysix M page.