Tag Archive for RF

Teardown, Repair & Experiments with an Agilent 8562E 30Hz – 13.2GHz Spectrum Analyzer

In this episode Shahriar repairs an Agilent 8562E 13.2GHz spectrum analyzer which does not power on. Upon pressing the power button the power LED briefly flashes and turns off. Teardown of the unit reveals a compact instrument where the power supply is rather difficult to reach.

The power supply block diagram shows various internal block functions which include startup, DC-DC converter and output regulation stages. In order to diagnose the instrument, the CMOS driver ICs were removed and swamped. An error during the installation of the gate drivers caused a cascade failure of the supply components! After replacing all the affected components as well as the DC-DC converter PWM controller IC, the power supply is repaired.

After powering on the unit it becomes clear that there are several internal self-test and alignment errors. The errors point to YIG oscillator failure. The YIG oscillator no longer has the full range of frequency tuning. The core of the YIG block is replaced with a spare unit from a different Agilent instrument. After re-alignment of the YIG the unit functions correctly. The principle operation of the YIG oscillator is explained and the internals of the defective unit are examined under the microscope.

Dino-Lite USB Digital Microscopes Review and Experiments (2017 Edition)

In this episode Shahriar demonstrates a series of new Dino-Lite USB Digital Microscopes released in 2017. Several models are shown:

  • AM7515MT8A – This unit offers 700X-950X magnification with built in coaxial lighting as we as switchable bright-field and dark-field lighting options.
  • AM73915MZT – USB 3.0 interface with one touch auto-focus, EDOF & AMR. The unit also offers up to 45FPS in lower resolution mode. The magnification range is 20X – 220X.
  • AM73115MTF – USB 3.0 with Dino-Lite’s longest working distance at 1X – 70X magnification. Capable of 20X at 10.5” working distance and 70X at 4.5” working distance.
  • AM5218MZT – HDMI/DVI output connections, new edge optics, minimal latency with fast frame rate up to 60FPS in good lighting conditions.

Furthermore the Vision M1 automated platform is also presented which can be used to manipulate the XYZ position of any microscope through a PC USB connection. All other presented accessories can be found on Dino-Lite website.

The above models are used to analyze several microwave amplifier modules and components. The ASIC die of a 30GS/s Track & Hold Amplifier (THA) as well an RGB light sensors are also closely examined.

 

Teardown, Repair & Analysis of an Agilent E4443A 3Hz – 6.7GHz PSA Series Spectrum Analyzer

In this episode Shahriar repairs an Agilent PSA Series Spectrum Analyzer. The instrument generates many errors during self-alignment and produces no measurements below 3.2GHz. The block diagram of the unit is thoroughly presented and various possible failure points are considered. Based on the observation of the noise floor, the most likely cause is the second LO module. The measurement of the LO power indicates that the second LO power is fall below nominal.

The second LO signal (at 3.6GHz) is generated by a DRO PLL module which is locked to 600MHz. The PLL is functional, however the output power is below -20dBm. Teardown of the module reveals a simple design with a doubler and filter. The filter (which is discolored) shows a huge loss likely caused by RF losses due to trace degradation. Thinning the traces provides some improvement and the remaining loss is compensated with a two stage RF amplifier. With this modifications, the instrument’s alignment errors are partially resolved.

The next problem is with the input attenuator at the 20dB range. This problem is simply resolved by providing lubrication on the attenuator solenoids after disassembly. The instrument is then used for various measurements to verify its correct operation.

Teardown & Repair of an Agilent N1912A P-Series Power Meter

In this episode Shahriar investigates a peculiar problem with an Agilent P-Series Power Meter. While the instruments works during startup, after about 10 minutes the LCD screen begins to flicker and become scrambled. Initial investigation reveals that the issue is not likely with the main motherboard since USB connection to the instrument and data-readout is possible even when the LCD screen is malfunctioning.

Teardown of the unit reveals a modular design where a ribbon cable connects the front panel to the motherboard. Moving the cable around affect the LCD which points to a faulty cable connection. The failure is at the only ribbon cable without a proper removable connector to the motherboard. The cable is cut, re-crimped and the solder joints re-worked. This appears to solve the LCD problem. The performance of the unit is verified by measuring the output power of the Tektronix TSG Vector Signal Generator.

Teardown, Repair & Upgrade of an Agilent E4405B 13.5GHz ESA-E Spectrum Analyzer

In this episode Shahriar explores the cause of failure of an Agilent E4405B ESA 13.5GHz spectrum analyzer. In a previous episode, an E4407B version of the ESA was repaired and upgraded which is helpful in debugging and analyzing this instrument. The instrument displays LO Unlock which is a familiar problem. After an overview of the system block diagram, the LO signal path is traced and analyzed for problems.

After some investigation, the problem appears to be identical to the E4407B model repaired before! The Hittite (Analog Devices) divide-by-4 static divider unit has failed and does not divide correctly at high frequencies. The component is replaced which restores the instrument’s functionality.

The LCD screen of the unit is also very dim. The CCFL tube and the inverter are replaced with an LED back light instead. The unit then produces a bright and vibrant graphs and text. The performance of the instrument is verified with a Keysight MXG signal generator.

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