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8594E CAL AMPTD successful but wrong results

Question asked by ermione on Jan 26, 2012
Latest reply on Feb 10, 2012 by tabbott
Good morning.
I recently bought an 8594E with 30 days ROR and I'm testing it. It was sold as "tested and working" by an industrial instruments seller, but instead it seems to have two problems.
First, the instrument has the option 130 "narrow resolution bandwidth" and CAL AMPTD fails with "CAL: NBW 200 Hz notch failed".
Examining the reference signal with 200Hz BW you see that the shape (of the filter response) is not gaussian, but it has a big undershoot on the right part. The reference signal examined with other filters
on the same board A130 is gaussian as expected.
So I took out the board, inserted W1, and attempted CAL AMPTD. This time the routine succeded, however, if you examine the reference signal, position it in the uppermost part of the screen (IE Freq 300MHz, Span 10KHz, Ref Level -8 dBm), you see the curve has a sharp "jump" from the -23  dBm to the -13 dBm, then the curve continue, jumps down from -13 to -23, etc.. It is clearly a wrong calibration factor from the CAL AMPTD, because if I switch off correction or I switch to linear scale, the problem vanishes. Repeating CAL AMTPD brings to the same results.
Probably, even if the 200Hz filter in the A130 board has indeed a problem, the CAL AMPTD failure with that board inserted comes from the same failure that bring to the "jump".
After fixing this, the A130 could be inserted again and the 200Hz filter shape corrected, (probably it's just a component out of tolerance - there is the CLIP for A130?).

At this point I'm facing the problem of fixing it, or returning to the seller.
I have already checked the reference signal, and it is more or less -20 dBm. I checked +10 V REF DET and -10 V REF DET and are ok, also 2v and GND. I calibrate frequency against a rubidium and it's now accurate, I checked cabling and it's all ok.
Someone could help?

Andrea Baldoni,
Ermione s.r.l. - Italy  

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