[Jon_G4MDC]

I have studied that synthesiser for a while now.
Loop 1 is tuning in 10kHz steps so that is not likely to be the problem.

The mix down local oscillator used in Loop 1 is tuned over 9.99kHz in 10Hz steps and it is likely to be here the problem lies - somewhere in Loops 2 and 3.

I am having trouble with the circuit in that area. It looks like Loop3 produces 50Hz steps which are then doubled to 100Hz before they feed Loop 1. VXO Q3009 in Loop 2 looks like it would be responsible for the 10Hz steps but tuning that affects both Loop2 and Loop 3. It is a bit confusing there.

Another strange thing is Loop3 is supposed to divide 4.075 - 4.57MHz down to 5kHz comparison frequency. That needs division ratios from 815 to 914. It is clear that Q3005, a TC9122, is only able to be programmed by BCD between 800 to 899. That is odd.

Anyway I would be looking closely for dry joints or short circuit whiskers on the PLL board around the shift register 4094s Q3031 and Q3032 and the TC9122 Q3005.