anyone familiar with Roland S-50 ?

[nashkato]

Hi ,
got this Roland S-50 with no output ( it is NOT the relay )
i recapped the Jack/audio board ( just realized missed 2 under the hood of IC7 / input )
recapped the CPU board
i got proper System Disks and S503 Sequencer Disks with dongle which do load just fine .
I get a nice Monochrome screen on Component Video output .
all voltages are good .
all functions seem to be working except the main thing , no audio
i´m gonna work backwards to the MUX and DAC to see if i can find something , but i´m not that firm in the digital area .
long shot probably , but does anyone have a suggestion at where to look ?
( except the usual " of course the relay u noob )
(relay is bypassed btw )

Thanks

 

[nashkato]

schematics

 

[Tubetec]

Im not familiar with the s-50 but I have done a fair few keyboards over the years .
Sometimes theres an internal memory back up battery , if its damaged the machine might not be able to boot up properly ,
There might be a system reset also , often it involves holding down a key(s) while switching the power button , that has sorted out similar problems Ive seen before ,usually its mentioned in the manual or service document .
Check the soldering on your output jacks ,thats a common fault with roland stuff as everything is very plasticy ,

Ive have seen plenty of issues with power supplies in Keys , leaky caps are a sure sign all isnt well , do a good visual check for dry joints especially around diodes caps and regulators , if it is the something with the main controler chip in my experience and especially with such an old model its unlikely to be an economic repair . or parts availability will snooker you.