Some more digging into the
-hp- 5245L with serial prefix 408:
Replaced some capacitors without much gain in terms of fixed issues. Counter is counting in CHECK and START mode on the last digit only. So measured the gate from the first decimal counter assembly A17(4), which is mainly working as the display assembly A18 is showing the correct counts, and found it to be stuck at +20V. WTF? The output is expected to be pulsed -15V/0V and the input on A16(
is expected to have a coupling capacitor.
So I pulled out all other decimal counter assemblies A10 to A16. output A17(4) is -15V without pulses. So checked the A16 assembly and found it is missing the coupling capacitor but goes direct to a clamping diode to +20V (similar to the boards A10 to A14). I already observed a difference in board population, the service manual says the boards A10 to A14 should be 5212L-4A and A15/A16 should be 05232-6010. In my device the boards were populated A10=05232-6010 and A11 to A16 are 05212-6016. The latter are not mentioned in any service manual I have and hp states them to be 600kc decimal counters only, so this one will not work in position A16 where 5Mc are expected. And I guess the former owner swapped boards without knowing that this caused havoc at the first decimal counter.
So tested the output stage of A17 and found Q9 to be dead (open emitter). Installed was a 2N2455, service manual says 1850-0163 which would be 2N2635. 2N2943 or 2N2048 should be fine too. But I have neither of them. Tried to replace with a silicon PNP without luck, have to measure the pulse at the base now.