Hi everyone,
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I am looking for some help on the repair of my 8753 VNA.?
I took some time trying to find the problem it myself with the service manual without success.?
The unit was working great and failed during my last filter mesurement. The signal is now noisy on port 1 and 2 (in S11,S22 ans S21), even if I do a new calibration.?
I have no error on power on. Have you ever entered this type of failure ?
I was first thinking of an ESD failure but it do not seems to be the case.?
The two input couplers mesure OK. I have 16 dB of coupling loss on port 1 and port 2. Visual inspection do not show any damage on the RF patch.?
The solid state switch also seems to be OK. I have 2 dB of loss between the input and the two output of the SP2T.?
In span zero mode I mesure a RF signal at the right frequency in the 1 MHz- 6 GHz band. Output power is also OK. The stepped attenuator seems to be Ok, signal source is there.?
The only problem I can see here is when I look at the RF out signal on a spectrum analyser, the RF signal do not seems to be locked. ?
When I reduce the SPAN on the VNA, I can see a lot of spike on the response.?
From what I understand, I now need to check the ?A7 Pulse generator diode stage and the A11 Phase lock board. The red LED on the A11 board is blinking but do not stay ON.
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Could you help me from this point on this repair ? Thank you ??
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S11 signal, port 1 open SPAN 6 GHz:
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S11 signal, port 1 50 Ohms load, ?SPAN 6 GHz:
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S11 signal OPEN SPAN 1 MHz
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S11 Signal SPAN 6GHz with 50 ohms load
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MattSNE