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HP8753C with Phase lock problems

Question asked by Peter_OZ1LPR on Sep 3, 2011
Latest reply on Oct 12, 2011 by Dr_joel
Hi all I have my very good friend Hp8753C that suddently got a serious failure. ´When I wanted to use it I got the failure no IF found check R input level.
I have the HP85047 testset connected correctly so the R input sees the output. I Have found out it was only from 30khz-86Mhz I se phaselock failure.
I looked on the output from the RF out through a 6dB splitter and get in CW mode (above 86Mhz) a powerlevel of -11dBm (analyzer power set to 0dBm. I read this is normal level. I then tried to move the A9 jumper. and did the Cal 44 Source definition that was done with succes. Then I did Cal 45 Pretune def also succes. Then I did Cal 46 Abus cor also succes. Then I was doing Cal 48 Pretune COR and this test Fails. I now checked the offset and the lowest frequency seen (when entering 300Khz ) is 160Mhz. And Now I can´t phaselock at all.
I did connect a signal generator to the amplifier input and checked from 3,8GHz to 6,5Ghz and get a relatively flat response. In the ends I se 2dB lower signal. So I presume the amplifier and Mixer is ok.
I did also check the REF section and Fraction/N section and the Comb generator also ok. I have extra sampler boards that are ok so I tried to fit in a new sampler on the R port no help.
So I am very stuck here what is my next move. Is it the Yig gone bad or ???

best regards a very dedicated Hp 8753C user.
Peter Hansen  

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