Korg ESK-701 Schematic Needed

[Paul Marossy]

Not exactly stompbox related, and I know this is quite a long shot, but will ask anyway:

I need service manual and/or schematic & PCB layout for the ESK-701 61-key part that is used in the Korg PolySix. I have the service manual for the PolySix already. I am looking for something  different. This is for the actual keys that you push with your fingers. There is PCB on the underside of the metal chassis which the keys are fastened to, which is loaded with diodes and those weird rubber contacts under the keys. I have searched online and have found nothing.

[ElectricDruid]

Hi Paul,

I've got a pin-out for the key matrix that I worked out at some point while trying to fix the inevitable dead keys on that rubber contact keyboard. Can't help you with a PCB layout or schematic for the actual keyboard PCBs themselves, but what I've got allows you to test pins on the connector and see if it's working.

I'll take a photo tomorrow and email you - ping me a message.

Tom

[Paul Marossy]

Hi Paul,

I've got a pin-out for the key matrix that I worked out at some point while trying to fix the inevitable dead keys on that rubber contact keyboard. Can't help you with a PCB layout or schematic for the actual keyboard PCBs themselves, but what I've got allows you to test pins on the connector and see if it's working.

I'll take a photo tomorrow and email you - ping me a message.

Tom

Cool thanks. I'll send you a PM with my email address

[Paul Marossy]

Just for the record, I think this basically what we have in the PolySix:

http://theatreorgans.com/virtualtheatreorgan/circuitry.htm

The first image shown, the 61-key matrix, is it as far as how the notes are arranged in banks of eight. Most likely 1V per octave arrangement. This satisfies my curiosity about how it knows what key you're pressing. At first glance the PCB on the ESK-701 is odd when you look at it, with the diodes in banks of four. I guess that corresponds with those weird rubber cupped contact thingies.

[ElectricDruid]

The first image shown, the 61-key matrix, is it as far as how the notes are arranged in banks of eight.

Yep! That's pretty much it! The uP powers up one group after another and then reads a byte to see which keys are pressed down.

Most likely 1V per octave arrangement.

Well, that's one of the odd things about the Polysix, actually - the VCO is a linear V/Hz type, not V/Oct. This is true of several Korg instruments, and pretty much no-one else (the only other V/Hz instrument I can think off the top of my head is the Paia Fatman). Not that it makes much difference to the keybed - it's just a matrix of switches read by the microprocessor. What the uP then does with that data is a completely separate question. Have a look at the Roland Juno 106 for an alternative implementation. In that synth, the uP sends data to a series of timer chips that then drive the waveform generation (the "Roland DCO" construction). The keyboard matrix on the two synths is identical (8x8 is just *too* tempting!).

[Paul Marossy]

Well, that's one of the odd things about the Polysix, actually - the VCO is a linear V/Hz type, not V/Oct. This is true of several Korg instruments, and pretty much no-one else (the only other V/Hz instrument I can think off the top of my head is the Paia Fatman). Not that it makes much difference to the keybed - it's just a matrix of switches read by the microprocessor. What the uP then does with that data is a completely separate question. Have a look at the Roland Juno 106 for an alternative implementation. In that synth, the uP sends data to a series of timer chips that then drive the waveform generation (the "Roland DCO" construction). The keyboard matrix on the two synths is identical (8x8 is just *too* tempting!).

Huh that's interesting.... good to know. Thanks for the info!