In this episode Shahriar takes a look at a non-functional R&S FSEK 40GHz spectrum analyzer. The instrument’s LCD screen back light no longer works and the front glass is broken. Furthermore, no testing can be done until these problems are resolved. The CCFL tube is replaced with an LED counterpart and a new front panel glass is also installed.
After power on it becomes clear that the instrument has other defects. The internal PLL is unlocked. It is observed that the OCXO module is cold and potentially not working. Examination of the LO board shows a bad inductor on the DC filter side. After this problem the instrument operates correctly but only for signals below 7GHz. After further testing it is discovered that the YIG tuned filter on the pre-selector path is not tuning at all. Eventually the fault is traced to some operational amplifiers on the YIG driver board. The repaired instrument is verified for correct operation.
In this episode Shahriar takes investigates the architecture and benefits of a precision sub-sampling wide-bandwidth oscilloscope. The teardown of the Agilent DCA instrument reveals a PC core combined with the acquisition board. The instrument without any plug-in modules does not perform any exciting tasks.
A 20GHz sampling module from eBay is available. However, the unit does not have an front connectors. New connectors are sourced from an old timing module and the sampling head is back to working condition. In order to test the unit, an Optellent OBP-04×10 4-channel pattern generator and error counter is used. The teardown of the unit reveals a simple design built around several transceiver ICs. The comparison between the sub-sampling scope and a real-time scope is also presented alongside measured results from the DCA.
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.
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.
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.
The Signal Path (TSP) is an electrical engineering video blog for industry professionals, students and hobbyists. TSP is a non-for-profit website dedicated to provide free education spanning a wide range of electrical engineering topics. Equipment reviews, tutorials and repair videos are posted regularly.