492P signal amplitude error and error 58


Happy Easter everyone,
my 492P was working when error 59 and then error 58 appeared for a moment on the screen, at the same time on all span / div the signal amplitude is low compared to the correct value (for example the amplitude of the calibrator of - 20 dBm is indicated as - 43 dBm, the frequency is correct). Error 58 is related to Phase Lock mode and actually comes out when the 492 P tries to enter in this mode, but fails and indicates "Error 58", even the LED on the "PHASE LOCK" button never lights up.
I checked the power supply voltages and they are within tolerance, I checked some components on the A4 and A5 boards (R3011), but without finding any problems. The suspicious thing is the error in the amplitude of the signals displayed at the same time as error 58. I think maybe the fault is not in the phase lock circuits but elsewhere, but I have no idea where.
Unfortunately I don't have the extenders for the 492 P boards.
I don't think it's a 1st mixer problem but it looks more like something in IF circuits.
I need help to fixing the fault.

Thanks for your attention.
-- Cheers

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