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Using two different 911 DME ECMs, tests were done without key ICs; EPROM, S705, S100, A/D. The 8051 address lines were active for 25ms then off for 12ms (reset).
Obviously there was no input to the ICV CMOS input pin 5. By only adding the EPROM, the CMOS ICV output functions.
Therefore, there's only three possible failure points; 8051, EPROM, and/or the circuit board. A simple scope setup is all that's needed!
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Dave
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