AKAI VX600 MATRIX SYNTHESIZER
It takes about 15 minutes for the synth to stablilise before doing a VCO tuning calibration. I looked at this on a DVM and ound the voltage sits at .22v then rises up to 2.5v over a period of 9 minutes. Why this is is unclear, bad capacitor perhaps? I have found that if the auto calibration doesn't complete, or takes an eternity you my need to check the DAC voltage. It should be 2.5v DC. Procedure is in the service manual. If your VX600 sounds bad this is possibly the reason.
Some pictures of the insides:
Voice Cards x6 voices play from bottom to top, when first powered on
Below voice cards. Opamps and multiplexers
There was some UV damage to the side panels. I'm not a fan of nicotine yellow so I must try and restore these.
The synth can have 6 separate outputs. I believe back in the day the VW-X6 DIN/PHONO cable was available. It possible to make your own using a 13 pin cable similar to those found on old Atari ST monitors, Digikey part number CP-1013-ND. The pinout for the VOICE OUT connector is shown below.