Memory in a 250466 PCB went flaky, so I tried my hand at repair. The PCB is the 3 ROM version, but with 4164 DRAMs. After desoldering the DRAMs, socketing, and installing some new DRAMs (all working now), I decided to see if I could switch the unit over to SRAM. It appears I and some other folks had similar ideas, as I see another project on Facebook to convert as well. I went a different direction and leveraged a small CPLD to do the conversion. After fighting last night with unsoldered pins, it is now working. I decided to play around with the unit and map out the address pins. Interestingly, I find that MA6 and MA0 appear to be swapped on the PCB. I verified that MA6 indeed goes to MA0 on the 6567, though without a schematic, it's hard to trace MA6 (it goes through a '257, etc.). Anyone have a schematic? (Zimmers does not appear to have one) And, does anyone know if pin swapping was done on other versions? -- Jim Brain brain_at_jbrain.com www.jbrain.comReceived on 2020-05-29 21:49:03
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