Hello
Dons analysis is excellent. After your description of pressing
the panel buttons, I'd say the cause for the stuck note/dead keys problem is a
corrupted/broken diode either on the panelboard or the keyboard. If you look at
the service manual page 7 (new board) or page 5 (old board), you will see, that
the bus P10-P17 is shared between the keyboard matrix and the panel board
KLM371, but the panel switches are returned to a different bus than the
keyboard. If a diode in this matrix is letting currents pass in the wrong
direction unpredictable things may happen.
If you had a battery leaking,
then a diode might suffer from it. I had it several times, that the glass body
of diodes got leaking, because the metal of the wire corroded, so a gap between
the wire and the glass appeared and humid air could reach the inner of the
diode, which again causes the diodematerial to change its
characteristics.
Unfortunately the service manual doe not contain a
schematic of the keyboard, so we cant tell which port line this
is.
Florian
On 20.04.18 03:33 , jhatzia@gmail.com [PolySix] wrote:
Thank you Don- you really nailed describing my situation. I'm working on it again now. And was trying to reply to your comment to get a new description on the hanging note but it started working again..?
After leaving the synth on for a while I couldn't even get Chord Mem or Hold buttons to react. After cycling the power they reacted again but had hanging notes.. I was then pressing all the key assign buttons and after some clicks it started behaving properly... Now all those dead notes are playing fine (except the last G, A & A# are still very dead).. Very odd. I wouldn't be surprised if it happens again. I'm still unsure where a fault like that would be found in the circuit.
Well- I still have to install about 3 new button cap holders and clean the volume pot, so I would be surprised if the issue arises again, if it does I'll make sure to update this thread.