Philips Frequency Counter PM 6603 Schematic

[hummel]

Hi all,
I'm hoping that maybe someone here might have a schematic/service manual for this device (Philips PM 6603 counter/timer). After a long life, Input A, the main freq. input, no longer responds. I'm pretty sure it's something simple since everything else still works fine. Probably just a blown transistor or logic gate (it's all 74xx TTL and discrete transistors) and would be easy to fix if I had a clue where to probe. (Actually, I do have a vague idea where the fault is but without a schematic I can't be sure. And I'd rather not yet start swapping out parts as a test method. It's always risky ripping into thirty year old stuff anyway. )
BTW, I did contact Fluke (nee Philips) in the Netherlands but they were unable to come up with anything.
Thanks!
- Michael (aka hummel)