Archive for Equipment Repair

Teardown & Experiments with Agilent mm-Wave W-Band (75 – 110GHz) T/R Module & Controller

In this episode Shahriar does a deep dive into the operation and architecture of Agilent/HP mm-Wave Extension Modules and Controller. The Agilent 85015A and W85104A work in conjunction and as the front-end for a W-Band (75-110GHz) S-Parameter T/R set. Although the mainframe system (HP 8510 Network Analyzer) is not available, a close look at the block diagrams reveals that the controller can be driven via external synthesizers to provide LO and RF signals. The detailed explanation of the entire system is presented from the ground up.

The full teardown of the mm-wave controller and T/R module are also presented and by reverse engineering the GPIB commands, the T/R module is brought to life. Several experiments show the full functionality of the system including a high-resolution CW radar demonstration.

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Teardown and Repair of an Agilent E4433B ESG-D 4.0GHz Synthesized Signal Generator (May 2019)

In this episode Shahriar takes a close look at a faulty Agilent E4433B 4.0GHz signal generator and vector modulator. This instrument is equipped with many of the most useful options such as dual arbitrary waveform generator and high-power output.

The instrument does not generate any error messages, however the output signal is ~20dB below specifications. After presenting the system block diagram and observing the output power characteristics, it becomes clear that the issue is with the mechanical attenuator. The teardown of the attenuator reveals faulty o-rings on the 5dB attenuation pad which has to be repaired with some flexible epoxy.

After the repair the instrument’s functionality is verified by measuring the output power with a power meter, frequency accuracy with a Rubidium frequency counter and the modulation accuracy with a vector signal analyzer.

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Teardown, Repair & Experiments with an Agilent N4901B 13.5Gb/s Bit Error Rate Tester BERT

In this episode Shahriar repairs a non-functional N4901B 13.5Gb/s BERT mainframe. This instrument is equipped with both the generator and analyzer modules which makes it fairly valuable. The instrument does not power on and does not react to the soft power button.

Teardown of the unit reveals a TD-Lambda Vega power supplies series which is a fully configurable switching power supply design. Even though the power supply in the instrument is completely custom, it is made from generic sub-blocks readily available on eBay. A replacement front-end is purchased to repair the power supply after detecting the problem.

The instrument also shows a minor problem with falsely detecting an overload condition on the delay control port which is by passed by installing an overwrite switch. The instrument performance is verified by generating and measuring various eye diagrams through a back-plane PCB board.

Teardown, Repair & Experiments with an EG&G Instruments 7265 DSP-Based Lock-In Amplifier

In this episode Shahriar takes a close look at an EG&G DSP-Based Lock-In Amplifier. This instrument provides excellent sensitivity for both voltage and current inputs and is based on a fully digital architecture. The instrument’s LCD screen is dim and unreadable. Furthermore, a few lines are missing from the LCD pointing to a failed zebra strip.

The instrument’s block diagram is examined and explained. The teardown reveals the structure of the LCD screen, front-end blocks and internal PLL. The CCFL back-light inverter is located and replaced with a low-voltage DC-DC converter for use with an LED strip. The instrument’s functionality is verified through a few experiments including measuring the 3dB bandwidth of an RC filter as well as measuring the photo-current induced in an LED using a synchronized infrared light source.

Teardown, Analysis & Repair of an Agilent E3646A Dual Channel Programmable Power Supply

In this episode Shahriar investigates a malfunctioning E3646A Dual Channel Programmable Power Supply. The power supply provides the correct output voltage on one channel. However, the second channel produces no output and continuously reads 0V and 0A.

Applying an external voltage to the malfunctioning channel produces the correct readout from the instrument display suggesting that most of the channel circuitry is functional. After a close examination of the power supply schematics, the problem is traced to a failed solder joint. The DAC output amplifier is disconnected from the output transistor and after repairing the colder joint, the power supply is fully functional.

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