[sdiy] Repairing Key Contacts (OB-8)

[jh.]

> My OB-8 had this problem terribly. Now it's completely better. I removed
the
> Toshiba keyboard and put in a new shiny 5-octave Pratt/Read with J-wires.
> Well OK, not new, but kept in plastic for years. :)

Hi Gene,

nice to hear from you, and yes, I envy you for that keyboard. (;->)
Something I wanted to do for years, but where would one find such
a keyboard ...

> I was considering changing the resistor values to a higher value in the
> keyboard diode matrix circuitry, so that the relative resistance of the
> rubber contacts would be less, but this would have required
experimentation
> and I was in a hurry. I honestly don't remember which resistor, or
> resistors, or what values, but somebody may want to investigate this as it
> may be the cure-all for everbody's OB-8 problems. The original pull-up
> (pull-down, whatever, I forget the circuit) values may have been too low.

Carefull with higher resistor values - that's dynamic scanning, and the
resistor
values determine the rising edge of the logic signals.
I had used too large values when I built the Four Voice keyboard clone
(don't
remember the exact value), and it didn't work. Changed it to original value,
worked.

JH.