I have a Roland SC-7 that I've repaired, here's the info FYI.

The unit had no output out of the L + R outputs on the back panel, or the right channel of the phones output of the front panel. Left channel of phones was working OK.

This unit has sixteen small 16v 10µF electrolytic capacitors across the board and could see most of them had some corrosion on their solder pads, likely from the caps leaking on to them. Tested them with an ESR meter and got no reading from ALL of them, all dead. The other electrolytics tested fine except for one 50v 1µF which was also bad. Replaced the bad caps and all functionality returned, sounds great.

So anyone having issues with these units, check those caps!