For more than a year I was searching the Internat for an obsolete
IC that's used in a Motorola S1344AAB Frequency Counter/Auto Tune
Deviation Meter. The Motorola part number 51-80329A60 is actually
a DM85L52 manufactuerd by National Semiconductor (the IC is
stamped 528 055178). I was able to get the data sheet from a
friend that had an old NS data book from the early 80's. The
part is a decade counter/latch with tristate outputs and will
cause readout or counting problems or an incorrect frequency
display. The counter also uses a DM85L51 that crosses to a
74LS173.


In the early 70's the unit was Manufactured by Systron Donner for
Motorola. Systron Donner's model number was SLN6407A-75. They also
manufactured a frequency counter model 6252 that's identical to the
counter section of the 1344AAB. Other SD frequency
counters, like the 6250 or 6202 use the same part.


If your looking for that part and you don't want to spend hundreds
of dollars buying a minimum quantity from a surplus dealer, Look
for any of the above SD models on Ebay. If your lucky and get one
for about $25, cannibalize it for parts.


Jack
WA9FVP