Maestro Sustainer SS-3 schematic help

[ilponiz]

Hi everyone,
just bought a 1974 Maestro Sustainer SS-3 from e(vil)bay but it doesn't work (no signal when the effect is engaged)
the  pcb is sealed with potting compund, it works with 2 9v batteries but, having no idea what the schemo would be, i don't know how to start the debugging
any help?
i will soon post pics of the pedal's guts

thanks in advance

poniz