TSP #129 - Teardown, Repair and Analysis of an Agilent 4338B (10uΩ - 100kΩ) Milliohmmeter
In this episode Shahriar repairs an Agilent 4338B milliohmmeter. This instrument is capable of measuring extremely small resistances down to 10uΩ while maintaining a DUT voltage of less than 20mV. The instrument powers on with the message ADC Failure. Investigation reveals that the instrument uses an obsolete ADC which must be removed from the board in order to reverse engineer its operation. While the ADC turns out to be functional, a PAL device which controls the ADC timing is faulty. A new device is salvaged from a donor board to complete the repair. The instrument is then used to measure several small known resistances.
In this episode Shahriar investigates a faulty Agilent E3631A 80W triple output power supply. The instrument powers on, display a fully illuminated VFD display before a long beep and dark screen. The disassembled unit reveals a two board construction. After an unfortunate finger burning experience, the fault is traced to pair of extremely hot voltage regulators and Zener diodes. The temperature of these components is measured using a thermal camera and reach 400C! The schematic of the power supply is examined and the appropriate components are replaced. The performance of the unit is verified after the repair.
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In this episode Shahriar reviews the Deepace KC901V 6.8GHz handheld network analyzer. This battery-powered instrument is an RF multi-instrument integrating VNA, spectrum analyzer, field strength meter, and a low-frequency signal generator. It can also perform signal port vector measurement and 2-ports simple vector network analyzing (S11, S21). The review is organized as follows:
01:24 – Instrument overview & block diagram.
05:36 – Full teardown along with RF and digital board analysis.
14:30 – Power on, calibration and S11 measurement of an antenna.
23:46 – Calibration for S21 and measurement of a tunable filter plus phase shifter.
32:23 – Distance to fault measurement of an SMA cable chain.
36:24 – Spectrum analyzer measurements and limitations.
43:16 – Signal generator measurements and issues.
48:20 – Other features and concluding remarks.
50:07 – Giveaway!
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In this episode Shahriar explores the functionality of the popular ESP8266 SoC chip. This IC incorporates a full ISM radio as well as the physical/MAC layer for 802.11b/g/n network communication. Furthermore it includes a uC core for code execution making it a low-cost candidate for Internet of Thing applications. This video uses a Sparkfun Thing evaluation board which also includes a LiPo batter charger, voltage regular, flash memory and all the I/O pins which are accessible to the user. The block diagram of the ESP8266 is reviewed as well as the schematic of the complete Sparkfun Thing board.
By using an Arduino library and the Blynk iOS application, a cell phone and the ESP8266 can simultaneously communicate with a server running the Blynk application and transfer data between the application and the module. In this demo various components such as NeoPixel (WS2812), OneWire temperature sensor and battery monitoring functionality are implemented. The code is available from The Signal Path website.
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In this episode Shahriar investigates some state-of-the-art energy harvesting ICs from Linear Technology. The LTC3105 is a highly efficient 400mA Step-Up DC/DC Converter with Maximum Power Point Control and 250mV Start-Up. After exploring the IC's internal block diagram, the evaluation board for this energy harvesting chip is presented. Various experiments, including the calculation of efficiency, maximum power delivery, start-up behavior and MPPC are presented. As a last experiment, a two stage energy harvesting setup using a solar panel and a super-capacitor capable of charging an iPhone is demonstrated.
The second IC of interest is the LTC3109 which is an Auto-Polarity, Ultralow Voltage Step-Up Converter and Power Manager Energy Harvesting chip. The block diagram and the evaluation board of this IC is presented. The ultra-low voltage capability of the circuit is demonstrated through the use of a Peltier cooler thermo-electric component to generate a 5V output voltage. As a final experiment, several ice cubes are used in conjunction with the thermo-electric generator in order to harvest enough energy to charge an iPhone for 30 seconds.
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In this episode Shahriar takes a look at a very high-end step attenuator designed by Rohde & Schwarz for their FSU family spectrum analyzers which cover over 67GHz of sweep frequency.
The attenuator teardown and architecture is thoroughly presented with focus on how the high-frequency performance is maintained in a moving environment. Furthermore, the individual attenuator pads are examined under the microscope for their construction and design where the 5dB pad failure can also be observed.
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In this episode Shahriar does an extensive review and teardown of the Keysight (Agilent) MSO-S Series 10-bit 20GS/s Oscilloscope. This scope supports bandwidths up to 8GHz and 400M points of memory per channel. With hardware 10-bit ADCs as well as an ultra low-noise front-end, this scope offers an impressive dynamic range on all four channels. All scope features are software upgradable.
The teardown consists of a close look at the acquisition board and the system blocks diagram. Various elements such as the ADC structure, FPGAs, memory and the time-base are all examines. The scope offers a +/-12ppb time-base with a 100fs jitter noise floor. Some basic performance measurements are also presented such as noise and SFDR.
The wireless experiment shows the performance of the scope in demodulating very low-power signals on an RF carrier. A -75dBm 2.5GHs QPSK signal can be demodulated by the scope. The instrument can also demodulate a 16QAM signal in presence of an interfering signal which is 44dB higher in signal power. All demodulation experiments are performed using the Keysight VSA.
The backplane experiments demonstrate the scope’s capability to perform jitter and noise analysis on multi-gigabit serial links. The built-in equalization software suites are used to find the FFE coefficients and those coefficients are used to perform hardware equalization in an FPGA communication link.
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In this episode Shahriar investigates the problem preventing a Fluke 789 PrceossMeter from powering on. The issue is fairly simple and is quickly identified.
The basic functionality of the instrument (DC/AC voltage, current, resistance measurements) are verified as well as the current delivery of the unit.
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In this episode Shahriar reviews the new Keithley 2460 Source Measure Unit (SMU). The Keithley 2460 shares all the touchscreen GUI advancements of the 2450 SMU and offers up to 100W of power in full four-quadrant operation. The combination of the 2450 and 2460 SMUs from Keithley offer a wide range of applications.
After a brief teardown of the instrument, several experiments are devised to demonstrate the TSP scripting as well as KickStart software capabilities. The experiments include LED failure modes, Geiger counter setup, Op-amp based voltage regulator characterization, temperature controller, non-linear transconductance emulation and data collection application.
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Since the creation of The Signal Path video blog in May of 2011 I have focused on producing the type content which is either difficult to find or difficult to learn. Despite being the foundation of human communication, RF and microwave electronics often seem like magic and my goal has been to demystify these concepts. The Signal Path blog provides a rich depth and breadth of electrical engineering topics and experiments. Equipment reviews and repairs are always accompanied with research and industry relevant experiments and tutorials. The aim of The Signal Path is to provide free education to everyone across the world, possibly the greatest gift from a human to another.
Any support you offer to The Signal Path will be put back into lab maintenance, improving the quality and frequency of video production and acquiring components to further diversify content production. As of August 2016, The Signal Path has produced over 66 hour of original material.
On behalf of all viewers from around the world I want to thank you for supporting The Signal Path.
Shahriar Shahramian, Ph.D. Owner & Host
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