OBERHEIM SYNTH

At 11:14 AM 2/17/09, you wrote:

>Did some work over the weekend.Here's what I found.The "D3" line is 
>loaded down to about 2 volts.All the other Data lines are reading 
>4.8- 5 volts.Pulled the PROMS, didn't make any difference.How many, 
>and what I.C.s can I remove in what sequence without damaging the 
>components to isolate the problem?

Remove any and all ICs that have a connection to D3 one at a time 
until the loading goes away.  You shouldn't damage anything if you 
turn off the power between each part removal.  You've already tried 
the EPROMs -- try removing the RAM chips, latches and buffers 
connected to D3 (A29 through A34, A102 through A105, A110 through 
A115 and as a last resort, try replacing the Z80.

Removing voice cards won't help, as this signal doesn't go directly 
to the any voices.

-- Paul White
http://www.electrongate.com/dmxfiles