I'm a bit in a hurry; but if I'm not mistaken the sustain switch is wired "normally closed"; when no switch is connected the tip connection is routed to ground. If this is true (again, no time to check in detail) removing the connector to the PCB would do no good - because that's what a pressed sustain pedal would "look like" to the circuit.
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[vintagesynthrepair] Re: Omni MKI Note String Sustain problem ... and more
2012-05-10 by Malte Rogacki