Vintage Synth Repair

Thanks for the info. As it turns out v1.7 has the RAM/ROM test, v1.8 and SER do not. There are 3 SRAM chips on the Vabatt supply and only two are in sockets. If I move the two chips that are socketed the problems definitely change. Depending on where the RAM chips are it kind of passes. The LCD flashes error for a moment, then says OK. My old eprom programmer had a ram test function, but the new one doesn't. :-( I will now have to wait for some SRAMs since I don't have any around. 

One other curious thing about this synth (I was doing an E!-ectomy on it), is that the Vbatt voltage was not making it to the chips. Not sure what happened there and have not removed the main pcb to look at the bottom. I replaced the battery with a small board of my own, along with my own diode and that is working properly now. It's almost like the battery trace on the bottom of the PCB is blown, but I find that hard to believe, unless there was maybe a screw floating loose or something... but the battery had been changed by someone else (butcher job really), so maybe they trashed the trace.

gb

--- In vintagesynthrepair@yahoogroups.com, Narfman96 - Narfland Studio <narfman96@...> wrote:
>
> Hi Grant,
> Â 
> It seems like the later rev eproms were missing some of the higher numbered tests. I'm positive the SER7 is...
> Â 
> Have you tried swapping the RAM chips with each other and seeing if the problem changes?