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HP 8753C A3 SOURCE problem

Question asked by kada1 on Nov 19, 2015
Latest reply on Nov 22, 2015 by kada1
Hello dear colleagues!
I have problems with my HP 8753C network analyzer. F/W version: 04.13. Options: NONE
The first problem is A3 Source. I tried to check the output regarding to "A3 SOURCE AND A11 PHASE LOCK CHECK" of Source Group Troubleshooting found in service manual.
And I found out only 3.8 GHz -40 dBm signal with slightly several MHz frequency hopping. This signal is independent of pretune frequency of VNA. I did not see any other harmonics except 3.8 GHz:
0 3 8 GHz  After it I measured the signal of Cavity oscillator and got  the 3.8 Ghz signal with much more power: about +10 dBm. So the Cavity oscillator is functional. Also I checked YTO oscillator and did not see any signal. I checked all power rails and they looks good. So I think the problem is defective YTO.
The question is how I can test other parts of A3 SOURCE module without YTO?
I tried to apply 0-3GHz 0dBm signal from generator to A3 SOURCE instead of YTO and measured signal with SA at RF OUT port of VNA. I can see the signal from generator, but there are many harmonics as well:
     100 MHz 0 dBm             500 MHz 0 dBm            1000 MHz 0 dBm           2000 MHz 0 dBm           3000 MHz 0 dBm
1 100 MHz 0d Bm 2 500 MHz 0d Bm 3 1000 MHz 0d Bm 4 2000 MHz 0d Bm 5 3000 MHz 0d Bm

Is it normal or should I see only one harmonic going from generator? As I understand it I see harmonic mixing components. Should they be filtered in the amplifier of A3?

Thank you to everyone who will respond!  

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