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HP 8719C repair

Question asked by Laurens on Oct 27, 2008
Latest reply on Apr 18, 2009 by met
Our 8719C was  loosing phase lock.

Opened it up, reseated a bunch of cards and it seems ok now, but the power output on port 1 and port 2 is poorly levelled.

Measureing the A58 MADS directly it drops off quite a few dB at high frequency the power output is ok up to 1.4GHz, then drops off by a couple of dB up to 2.5GHz, then it's fine again (it switches out the low freq. mixer at 2.5GHz), until it starts to gradually drop, being less than 0dBm output at 13GHz. For normal operation it's not a huge problem, as the instrument 'calibrates out' the source power error, but I'd like to fix it. ALC On or Off makes no difference at the higher frequencies (but it does cause >+10dBm at <1GHz)

I think it's the A58 MADS board. YIG and mixer power is fine. Are there any specifications for the gain and gain flatness of the MADS assembly?  

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