Yet another buggy Ensoniq keyboard .. SQ80 - low output

[veinmelter]

took in a sick SQ80 from a friend
love hate relationship with these damn things

screen turns on fine, sends midi signal, so the brain seems to be doing fine

but it has very low output and the data slider doesn't work
(can be just barely heard if i run it into an amp and blast the volume)

so after running through the buchty service manual, tested all the power supply terminals, no fuses blown, cleaned display board connectors
http://www.buchty.net/ensoniq/files/...ice-manual.pdf

I guessed it was the sliders

so I ordered new slider potentiometers from syntaur, replaced those

NO GO

any idea where to look next?

the display board ribbon connectors maybe? they look in good condition to me..

really seems like it's just the sliders that aren't reporting properly, for whatever reason

[Enzo]

So look at the sliders. Is ther 5v across the data slider? Audio across the volume? (Assuming my recall is OK) Does sliding eth data slider cause an even sweep of voltage at the wiper? Does volume slider actually work in circuit? Just because you replaced a slider doesn;t mean the circuit it is in functions.

[veinmelter]

finally getting back to this

thanks for your reply Enzo

I've looked over this a bit more, decided to check the voltage and current coming from the display board into the main board via the J4 connection. At the connection, the voltage and current are varying when I slide the sliders up and down.

So I am now going through and attempting to read the schematics and test across the main board?

this is not easy, i'm a beginner by all accounts

http://www.buchty.net/ensoniq/files/...80-digital.jpg
http://www.buchty.net/ensoniq/files/...cs/sq80-a1.jpg
http://www.buchty.net/ensoniq/files/...cs/sq80-a2.jpg

[veinmelter]

when i said current in that last post i meant resistance

voltage and resistance at the headphone out remains the same no matter where the volume slider is