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HP 8664A Must do MW Loop Adjust

Question asked by BoinFinland on Dec 20, 2014
Hi All,

My 8664A opt 04 gives the result code +2,433,311 after running the Self diagnostics Special 320.
The instrument has been at the local service center after phase noise issues and was doomed "not worth repairing".
When I run the MW Loop Adjust procedure everything looks fine.
341: MWL Cal 2  +1000 ... +1005 (mostly stable at +1000) -> OK
342: MWL Cal 3  -88 ... -93 (-93 few times) -> OK
R154 set to 7 just as the MWLOOP ASSY ADJ sticker says -> OK
Running ReCal Special 171 runs fine and returns the code 0
Re-running the self diagnostics gives the same error code +2,433,311.

What else can trigger the error code?
Noise in the MW loop?
Supply voltage variations?

Any ideas or experience of this?
Thanks for any hints you may have.  

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