It's in an old (mid-80's) industrial machine. The French mfr. is out of
business. The circuit I'm trying to resurrect takes a digital measuring
encoder as input and displays the measurement on 7-segment LED displays.
Display went wonky for a few weeks, then went blank, entirely. DC voltages
and ripple are all good. Tried reseating socketed components; no joy.

Lacking any documentation, I'm going to try some "shotgun" troubleshooting by
replacing the major components on the board (they're socketed).

Large components include:
D8085AHC
D8155HC
D8279C-2
uPB8212C
All parts NEC mfr.

When replacing with components available today, what are my limitations? (For
example, I know "H" means HMOS, and that is a "must".) What else should I be
careful re. the letter digits of the p/n's when selecting parts with the same
numerical digits of the p/n's?

I know that the 8279 is a programmable controller, so replacing that without
having the source code to program it with, is out of the question.

Just trying to help a client keep this otherwise good machine in service and
avoid "binning" it.

Thanks,
--
DaveC

This is an invalid return address
Please reply in the news group