Thanks again, Neil. You're correct that the datasheet shows all the details
of the operation of the counter/display IC.. and going thru the complete set
of I/O signals will likely show if the IC is functional.

I'd still like to have a manual and schematic to see what the recommended
uses or limitations of the counter are, and to confirm that the correct
parts are present.

BTW, the unit was factory built, manufactured in Japan, so the so the design
and features could be nearly identical or similar to counters of other brand
names.

The 80s were around the time when a lot of U.S. domestic test equipment
manufacturers started selling imported models.. Leader, BK Precision etc.
Browsing catalogs back then, it was common to see numerous brand models that
were nearly identical except for cosmetic differences.. front panel, knob
styles etc.

--
Cheers,
WB
..............


"nesesu" wrote in message
...

This data sheet looks like it gives enough information to trace
through the operating parameters of the chip in your application.
Heath was known to utilize the 'typical application' circuits of the
manufacturers, so I would not be surprised to find the data sheet
fairly close to the circuit you have. This also explains the various
functions of the controls.
http://www.electroniccircuits.gr/files/ICM7226.pdf

Neil S.