ARP Quadra computer problem
OK, cross posted over in analog too, as it's an analog keyboard, and there is a lot of tech knowledge over there.
Anyway, know this is a rare machine. Here is the deal, the 16 programmable switches don't program. The actual function switches still work, and the program change switches appear to change (but not really, mostly just all on or mostly all on) so it doesn't seem that whatever programs were in there are still actually in there.
Also, the pitch for the lead synth scanning mechanism ("interval write") works as well. However, when switching from "Lock" to "Load" the function switches all freeze (basically you're supposed to swith to load, turn various switches on or off and then then that program will be remembered)
So, because the interval write is working, it appears as though the microprocessor system is working, but I can't write to memory. The system is based around a 8048 and the RAM is a 5101. My completely uneducated guess would be the RAM chip as the only function that doesn't seem to work is writing to RAM.
The RAM is easily obtainable. I recently sold my DATA I/O box, so even if I could get the firmware for the 8048, I can't program it. But again that doesn't seem to be the problem.
I'm ok with something like a blown capacitor in a power supply, but computer circuits aren't exacltly my forte.
Any thoughts? I'm thinking maybe the 5101 chip? (Also, ARP's are a bitch to work on the way the PCB's are under the sliders. Also, I'm not sure if hte RAM is socketed or not, as the board faces the wrong way.
I'm somewhat reluctant to go pulling the microprocessor board, just to see if the RAM is socketed, as the Quadra has been extremely tempermental the whole time I've owned it (since 1988) but I'm also fearful of cascading casualties. I did come across a website regarding old video games (which also share the 8048/5101) that stated the 5101 was susceptible to battery leakage/failure. Don't know the context, but I've been pretty remiss in changing the 3AA batteries that power the memory. My completely uneducated guess would be the RAM chip, as it seems the only function not working is writing to RAM. Also, I don't really need the 16 program locations. I am never going to gig with this keyboard, and I am perfectly happy turning on and off whatever section I want when I need it. The only reason I'm concerned is with having something else fail as a result of this failure.
