Ok, so the latest PCB's arrived. This design is using the same prescaler chip as the HP design, with the same prescaler bias network.
I think I'll have to order a couple more parts, pending a raid of the parts bin, but soon I'll have a much closer replica to test out and see how it works.
Fingers crossed that the prescaler chips I sourced from China are genuine parts.......
Jared
Jared Cabot