Hi,
The Polysix scans 8x8. So 9 keys failing would be rather odd.
But from G1 downwards it's only 8 keys... So we're back in the game.
The low eight keys are read through D0 (see attachment).
Check for continuity from the Kyboard PCB to MIDI Module/IC5/pin4.
Good luck,
Johannes
On 29.07.12 00:27, Peter Mörck wrote:
> Hi,
>
> Speculations ahead. Skip to next part if not interested :)
> There are 16 wires going to the keyboard.
> I can't from the schematics tell if the keyboard is scanned as 8x8 or 7x9.
> 8x8 would probably be more "natural" as it allows the P-pins to set "row" and the DB-pins to read column, so to speak.
> It requires 8 partial scans, scanning 8 keys at a time. Maximum number of keys 64.
> On the other hand, 7x9 might be faster since it only requires 7 scans, scanning 9 keys at a time while still allowing a maximum of 63 keys.
> Since we only have 61 keys, and you say 9 keys are dead, I would guess it scans as 7x9.
>
> Next part:
> I suspect one wire to the keyboard is open circuit somewhere, or perhaps one of the diodes on the keyboard board?
> I don't remember how the diodes are connected on the keyboard and I'm too tired to figure it out :)
> Do continuity testing from the solder side of the keyboard connector to where the cable is soldered onto the keyboard board.
> But first, wiggle the keyboard connector a bit and then press it down firmly and see if that helps.
> It's probably attached with some glue but .. well.. heh..
> There are no components between the keyboard and the keyboard scanner controller, though there are other things on those lines as well that might interfere if fried, though I still suspect it's just a mechanical problem with the connector or some solder joint.
>
> BR,
> Peter
>
>
>
> ----- Original Message -----
> From: feline1973
> To: PolySix@yahoogroups.com
> Sent: Saturday, July 28, 2012 11:33 PM
> Subject: [PolySix] dead keys :(
>
>
>
> My Polysix has developed a fault with its bottom 9 keys (G downwards) -
> first they started intermittantly failing to trigger when pressed,
> then they started doing odd things like being silent when held down together...... and now they're all just dead.
>
> I dismanted the keyboard assembly and cleaned the conductive studs and contacts on the circuit board - didn't help. I doubt very much they're the problem, as swapping different rubber stud-holders around doesn't change things.
> I'm wondering if the multiway cable between the keyboard and voice board could be the culprit? Maybe just one of those yellow wires is dud?
> I can't even get it out to swap it, the keyboard end is stuck in its socket.
>
> Any suggestions?
>
> (Oh, and it all plays perfectly if trigger exterenally via MIDI - I have Johannes Hausensteiner's retrofit)
>
> David
>
>
>
>
>
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