Vintage Synth Repair

>>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)<<

more likely to be a power supply problem- can you check (or get
someone to check) the power supply rails inside the thing? there
should be 12s & 5s in some combination, same as in 99% of digital kit.
+12, -12, +5, -5, & maybe some more of the same for analogue circuits... 

look at the big capacitors around the power supply- prob'ly one of
them has leaked a bit or otherwise failed. or it could be a rectifier
bridge that's failed. 
are any of the chips socketed? you could try "crunching" them home
gently...
if it's not this, you may discover some combination of key-presses
that re-initialises the box, if it is a dead memory battery. this too
should be checked for terminal voltage (with the box off) & leakage-
many of these batteries can damage circuit boards if they are badly
sited & have leaked. poly-6 owners know all about this!

hth-
duncan.