Not easily. Is the circuit identical to the original NRG? If it is then check carefully for faulty/incorrect components, bad solder joints or shorts, especially in the circuit between IC3 and the varactor. If not then you're probably best changing it to match the original.
Also when you say it doesn't lock, have you actually measured the frequency? Or are you just basing that on the lock LED not coming on? Could be that its locking fine but something in the lock detect circuit isn't working.
Looks fine so not that then.BriansBrain wrote: ↑Sat Sep 13, 2025 1:12 pm Sorry I posted the wrong results before... should be
Cold = +5.0211V
Warm = +5.0279
Out of interest, what happens if you turn it off, short out all the caps in the loop filter to discharge them, then turn back on again? Does it lock up straight away or take ages again?