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HP 8753A Source Power Problem

Question asked by ffranulo on Apr 20, 2015
Latest reply on Apr 30, 2015 by ffranulo
I have an old HP8753A network analyzer and I have problem with output power. If I try to adjust source power I see no change in the power output level. I did some troubleshooting and I can see voltage change on the on the source module (A3) PWR test point if I change power level on the instrument. According to my spectrum analyzer output level stays in the range between -15 to -11 dBm depending on frequency. I am unable to test see power levels above 1.8 GHz range. On the INT test point (TP5) on the ALC Board I measure 670 mV regardless to the power settings on the instrument. On the source Bias board on the test point TP5 LM see -0.5V. E9 point on the source bias board shows 0V (that is the rectified output of directional coupler on the source output). To me this looks like I have bad amplifier in the source module. I wonder if anybody here had the same problem and what options I have to fix this problem. Thank you.  

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