I have tried replacing U1050 (74LS74) and U2050 (74LS10) on the A50A3 offset mixer board, but without success.
I also tried to replace the 1st mixer, but nothing has changed.
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).
Also the error 58 related to Phase Lock mode 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.
What could I check?
I suspect it could be a problem with the 1st local oscillator or its driver.
Thanks for your attention.