Archive for the 'Agilent Equipment' Category


Agilent E4402B Repair

A few months ago I was able to pick-up a few spectrum analyzers at reasonable prices. These were a HP 8591E (1.8 GHz) and an Agilent E4402B (3 GHz); both with tracking generators. The 8591E was in really nice physical condition and worked perfectly. Here is that unit on my bench with a 900 MHz tone shown being driven by my Fluke 6060B RF generator.

8591E SA-small









The E4402B on the other-hand looked a bit more used and was not operational on the receive side, though the tracking generator seemed to be OK. The E4402B was not functional with a steady tone at 800 MHz with no input. The board from China was $1700 and $3000 from Agilent. Fortunately this video by Shahriar over on The Signal Path Blog gave me hope that the problem was an Agilent prescaler part that was directly substituted by a Hittite HMC365S8GE DC-13 GHz prescaler IC.

That did in fact fix the issue with the main RF board. Below is the result showing the E4402 being aligned

E4402B SA Align









and then post-alignment.

E4402B SA









Next will be the RTC/NVRAM module because the unit is 13 years old base on the date of manufacture and the NVRAM battery cell is gone. As a result, the calibration settings cannot be stored and clock settings do not persist across a power cycle. Luckily, Agilent used a STMicro part with an innovative removable crystal and lithium battery module they call SNAPHAT. The 28-pin RTC/SRAM module has 4 female pin sockets as part of the package and the crystal and battery module plugs into and snaps onto the IC. The part number for just the battery unit is M4T28-BR12SH1 and was available via DigiKey.

Update (10/15/2014): Just installed the SNAPHAT part in and re-calibrated the unit, set the Date/Time, etc. All good with no more errors or messages – done.