Hi,
I just opened my Navtel 4950 frequency counter to see if there was any ROM that should be backed up, and I wasn't even able to ID the main processor !
It's a white ceramic DIP-40 IC with gold cap, no mfg logo , and two lines of markings :
2501A
7622
The latter is no doubt the datecode, which fits with the rest of the ICs. I'm having trouble with "2501" : the only thing I found was references to an AMD "AM2501 counter", but apparently that was a DIP24 chip (not very authoritative data; couldn't even find a datasheet). It would have been a likely candidate though : this meter is not very sophisticated; I could well believe that the display be driven directly by a BCD counter.
So, is my info on the AM2501 wrong, or is there another 70's-era IC that is a more likely fit ?