In this episode Shahriar takes a look at a R&S SMBV100A Vector Signal Generator which does not produce the correct output level. Despite passing all self-tests and ALC checks, the output power level is far below expectation. The output also shows a high-pass frequency response.
The (heavily simplified) block diagram of the instrument is examined and discussed. The teardown of the unit reveals the output RF board which is presented in details. Since the instrument cannot detect the failure internally, it is very likely that the fault is part of the RPP output RF relay. The circuitry as well as the datasheet of the components are examined. Measurements show that the output RF relay is never activated due to a faulty PMOS transistor. After transistor is replaced, the unit shows the correct output level. The baseband generator functionality is also verified.
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 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 reviews the new Tektronix AFG31000 Arbitrary Function Generator. The AFG31000 series with InstaView™ technology is the first high-performance AFG with built-in waveform generation applications, patented real-time wave monitoring, and a modern user interface. The instrument is capable of 2GS/s waveform generation up to 250MHz and 14-bits of vertical resolution. This review is organized as follows:
00:08 – Introductions
01:01 – Front panel, rear panel and instrument design
03:44 – Detailed teardown, analysis, architecture and components
17:30 – GUI overview and basic functions
20:25 – Broadband FM modulation experiments
23:55 – InstaView experiments with a non-linear impedance
35:38 – Equation editor, waveform builder and advance sequencing
51:21 – Concluding remarks
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.