Monday, December 18, 2023, 16:43:43, chinesejames1990 wrote:
My guess is CAL data is broken due to faulty original EEPROM 28C256. And the worst thing is, I can't read it out in good shape nor can I re-calibrate the unit. Various selftest errors may be caused by bad CAL data.
Is there any way to restore it, or any way to measure in order to re-calibrate the whole unit just like what factory did for people like us-individuals? ,_._,_
If you have access to a programmer with valiable supply voltage, try to read your chip many times while decreasing supply voltage gradually, and write every read image separately. I had similar problem with Xicor X2816 chip in Marconi 2955, and finally I was able to generate correct image by analyzing files read from such "leaking" chip. If you are really lucky, you may find voltage at which chip will read almost stable with correct data (say 9 of 10 reads will be the same). It is same method that we used to recover "leaky" EPROMs in the past - IIRC, I already wrote here or in time-nuts list with more details.
