Tag Archive for Repair

Teardown & Repair of an Agilent N9020A MXA 10Hz – 8.4GHz Spectrum Analyzer (November 2019)

In this episode Shahriar troubleshoots a defective Agilent N9020A 8.4GHz spectrum analyzer. The instrument reports LO Unlock and refuses to perform any sweep at all. The complete block diagram of the instrument is presented with focus on the LO generation blocks.

The teardown of the instrument reveals the individual assemblies presented during the block diagram overview. After a few measurements, it is concluded that the LO Synthesizer module is faulty. The module is presented in detail and various components and signal paths are identified. Extensive measurements are carried out until the fault is traced to problems in the varactor bank of the main VCO. After the component replacement, the instrument is fully functional. The X-Ray of the synthesizer module is also presented during the repair.

Teardown & Repair of an Agilent 1169A 12GHz Smart Active Probe (And a Puzzle!)

In this episode Shahriar examines a failed Agilent 1169A 12GHz Smart Active Probe. The probe does not get recognized by the oscilloscope and therefore cannot be calibrated. The instrument uses an I2C interface to the probe to download the probe’s specifications and characteristics.

The probe teardown reveals a simple I2C EEPROM IC. After removing the IC it becomes clear that the chip is damaged and must be replaced. A duplicate probe is used to copy the EEPROM data onto a new IC which revives the probe. With the help of the community, the CRC checksum code is discovered and the probe is assigned a new serial number.

Teardown, Repair & Analysis of a Rohde & Schwarz FSEK 20Hz – 40GHz Spectrum Analyzer

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.

Teardown, Repair & Experiment with an Agilent DCA 86100A Wide-Bandwidth Oscilloscope

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.

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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