Mark 1 Rhodes Super Satellite Weird Sound

[eywalian]

Hello! I recently acquired a 1975 Rhodes 73 with Super Satellite System. When using the master amp through the 4 pin cable it makes an odd noise (attached). It only sounds when pressing multiple keys. When going through the Preamp output A on the master, from the quarter inch accessory plug it works perfect, same as going from the accessory direct to the slave amp. Is this an issue with the preamp? Cold solder or bad caps? I've attached pictures of the circuit boards. Any help/guidance would be incredibly appreciated.


https://imgur.com/a/rhodes-SasAsna