Vintage Synth Repair

Hi Folks,

I have a Roland SDE 1000 Digital Delay that I used 20 years ago in my 
studio -- now it doesn't work.  Digital Delay flashes as delay knob 
is turned, but the output is pretty garbled, and the number panel 
doesn't show any info (except when turned from on to off)

I took it apart and pulled all the connectors and cleaned.  Seemed to 
help a bit, but not much.

I was wondering if it might be the battery, as the manual says to 
replace every 5 years.

any thoughts on this one?  I'm guessing I could probably find the 
battery on ebay and replace if somebody thought this would solve the 
problem

If not, I'll probably just sell it as nonworking.

Thanks!

Fred