{"id":946,"date":"2018-09-29T20:42:42","date_gmt":"2018-09-30T04:42:42","guid":{"rendered":"http:\/\/wonghoi.humgar.com\/blog\/?p=946"},"modified":"2023-04-23T03:49:25","modified_gmt":"2023-04-23T11:49:25","slug":"agilent-n9340b-handheld-spectrum-analyzer-repair-and-teardown","status":"publish","type":"post","link":"https:\/\/wonghoi.humgar.com\/blog\/2018\/09\/29\/agilent-n9340b-handheld-spectrum-analyzer-repair-and-teardown\/","title":{"rendered":"Agilent N9340B Handheld Spectrum Analyzer Repair and Teardown"},"content":{"rendered":"

I received an Agilent N9340B 3Ghz Handheld Spectrum Analyzer with a note that it passes all self-tests but does not respond to input signals. I took the gamble that it’s the RF input connector got disconnected somehow.<\/p>\n

I opened up the case and noticed that the 40Mhz cable was unplugged, so I was half-correct. I connected it and got a signal at the precise frequency, but the amplitude doesn’t look quite right. It’s around -20dB off. When I scanned it across the full 3GHz band, I noticed the amplitude roll-off when I scan below 800Mhz, and I got very little signal left when I get to somewhere near 10Mhz.<\/p>\n

I tried running a user calibration with a 50Mhz CW source but it failed amplitude calibration. Apparently the unit is not fully working. No self-test errors though.<\/p>\n

So I opened up the unit and the RF section. The front side of the board doesn’t have any visible signs or unusual smells, so I suspected the improper gains is caused by the input attenuator HMC307:<\/p>\n

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I was about to order the chip, but because of the lead time, I decided to just take a picture of everything and analyze it off-line:<\/p>\n\n\t\t