I believe as my colleague say: Replace battery for CMOS, and then Clean the EPROM+ CMOS, pins from rust, and dust with
Electronic contacts cleaners.
2) Reset the CPU, and test the VCC is the regulated power supply is ok in tolerance, and Clock for the Range in MHZ.
Otherwise, the RESET will do not have effect.
Clean all Edge board ( this cause most of 70% of electronic problems) !!!!.
Finally if the problem persist, i can supply the parameters, send me your email, i can not provide the my, by rules of
Forum.