Congratulations!
Half the work has already been done. We found a fairly thick hook that can be pulled well.
The EPROM Chip Enable signal “accumulates errors” and becomes unstable over time.
Note: The likely cause could be one of the address/data lines. The CE signal only indicates the result.
Let's move on.
G'day All,
Should we be checking for any glitches with the power supply when the controller is first powered up?
If you read Section 2.4 as per attached it stresses the importance of power switching.
Yes, precisely.
Probably we have some power line glitches here.
On the trace from the faulty board some other one signal with a repetition frequency 214 kHz is very noticeable.
Without changing the oscilloscope adjustments, look at the power bus IC23 Pin 14 and GND Pin 8.
Also have a look at EPROMs power line.
Next, check for ripple on electrolytic capacitors.
If you find similar signals post them here.