In this episode Shahriar investigates the failure of a Voltech PM3000A 3-Phase Universal Power Analyzer. This instrument is capable of advanced measurements on power profile and performance of a DUT. The unit shows “Voltage & Current OVERLOAD” condition on all channels even without a DUT connected.
The teardown of the unit reveals the isolation techniques used between the analog sampling heads and the main digital/DSP board. The instrument uses a combination of transformers and optocouplers to provide power to the sampling heads and receive digitized data from the voltage/current ADCs.
Close examination of the unit shows a faulty capacitor on the AC power supply feeding the sampling heads. The capacitor is replaced which corrects the overload condition. The unit is then used to measure the power profile of a simple glue-gun. The PF and THD measurements show that the glue-gun is equipped with a triac for power control; an expected result for a simple glue-gun.
In this episode Shahriar repairs a malfunctioning Agilent N5182A MXG Vector Signal Generator. While the instrument operates perfectly above 250MHz, below 250MHz the output is very low with a significant increase in the noise floor.
The block diagram of the synthesizer is presented showing various RF signal paths. It is shown that the sub-250MHz band is derived from a hetrodyne section which is where the problem located. Using a EM probe, various signal flows are discovered on the main board and compared with the block diagram. The main problem is traced to a doubler circuit which generates a 1-GHz LO signal for the hetrodyne section. The doubler comprises a transformer coupled to a dual diode surface mount IC. The IC is replaces which restores the doubler functionality and repairs the instrument.
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.
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.
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.
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.