TSP #110 - Teardown & Repair of an Agilent N1912A P-Series Power Meter
In this episode Shahriar investigates a peculiar problem with an Agilent P-Series Power Meter. While the instruments works during startup, after about 10 minutes the LCD screen begins to flicker and become scrambled. Initial investigation reveals that the issue is not likely with the main motherboard since USB connection to the instrument and data-readout is possible even when the LCD screen is malfunctioning.
Teardown of the unit reveals a modular design where a ribbon cable connects the front panel to the motherboard. Moving the cable around affect the LCD which points to a faulty cable connection. The failure is at the only ribbon cable without a proper removable connector to the motherboard. The cable is cut, re-crimped and the solder joints re-worked. This appears to solve the LCD problem. The performance of the unit is verified by measuring the output power of the Tektronix TSG Vector Signal Generator.
In this episode Shahriar demonstrates the effort for collecting affordable components and instruments in the past year to be able to generate mm-wave frequencies in the lab. The main goal is to generate synthesized CW signals beyond 26.5GHz and to be able to analyze them on the Keysight MXA Spectrum Analyzer.
Several instruments and components are which include the HP 83752B Synthesized Sweeper, HP 83556A mm-Wave Source Modules between 26.5-40GHz and 40-60GHz using doubler and trippler architectures, HP 8349B 2.0-20GHz amplifier, HP 11970 series harmonic mixers and OML DPL313B diplexer. Combining all these instruments along with various waveguide to coax converters mm-wave generation and detection is successfully demonstrated.
Finally, a full teardown of the mm-wave source module is presented which includes the preamplifier as well the waveguide module with very interesting design architecture.
The Signal Path
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=eUpxhZ0UEt4
In this episode Shahriar takes a look at a SRS SR830 DSP Lock-in amplifier. The repair of the instrument is fairly simple and provides a quick look at the internal construction of the unit.
The instrument is then used for characterizing nonlinearities of a pair of matched diodes in large-signal operation. A Tektronix 4-Series is also used alongside the SR830 in DDC mode to show the harmonic behavior of the DUT in frequency domain. The SR830 is able to discern extremely small variation in temperature between the diodes and the resultant 2nd order harmonic changes in both amplitude & phase.
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=figDqnsQD88
In this episode Shahriar attempts a difficult repair of a Tektronix RSA real-time spectrum analyzer. This well-equipped instrument reports several error messages during startup POST including LO Unlock as well as Signal Path failures. The service manual of the instrument does not provide any detailed block diagram and no schematics. Most failures require the instrument to be serviced by the Tektronix factory. The equipment has various advanced options including 110MHz analysis bandwidth, digital modulation analysis, wide-band IF output and deep memory.
The teardown of the instrument reveals a multi-board, multi-module design. The top of the instrument contains all digital blocks and boards while the bottom of the instrument houses the RF deck assembly. The RF deck is broken into various stages such as attenuator, RF switches, first converter, second converter, IF block, reference synthesizer and LO generator. For the purposes of addressing the YIG problems the LO board is examined. The problem is traced to two components, both dividers in the complex PLL system of the LO subsystem. The LO board is fully analyzed and described and the defective components re replaced.
The repaired instrument is tested for various functionality including DPX, de-modulation and measurement beyond 8GHz CW tones. The instrument passes all self-tests, alignments and detailed diagnostics.
The Signal Path
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=30VxmTnhvfQ
In this episode Shahriar goes over the operation and principle theory behind Lock-in Amplifiers. The SRS SR530 is one of the most iconic lock-in amplifiers ever made and since it offers two channels it can be used to perform very interesting experiments across many domains. After reviewing the block diagram and equations governing the theory of operation, a brief instrument teardown is presented.
Two unique and interesting experiments are also presented. In the first experiment the instrument is used to measure the speed of light. This is accomplished by measuring the wavelength of sound at 20kHz using a pair of speakers and a function generator. The distance between the speakers can be carefully adjusted and the relative signal strength from each lock-in channel is measured and thus the wavelength can also be measured.
In the second experiment the sensitivity of a red LED to blue laser light is measured. Due to the semiconductor composition of the red LED as well as its red plastic casing, the responsibility of the LED to blue light is extremely low. A chopper is therefore used to lock the light to the lock-in amplifier's reference input. The measured induced current is measured down to very low optical level in the order of hundreds of fempto (10^-15)
The Signal Path
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=rzzliN_vTKs
In this episode Shahriar investigates the failure of an Anritsu MS2712B 7.1GHz portable spectrum analyzer with built-in tracking generator. The instrument is missing the main firmware flash card which is easily replaced. A full teardown of the instrument is presented with focus on both the tracking generator PCB and main RF deck. Various ASICs and microwave components are closely examined. To help with removing and replacing many microwave screws, a Hitachi/Metabo electric screwdriver is used which can be purchased here:
https://amzn.to/2We8yoP
After re-assembly of the unit, it becomes apparent that a mechanical push on the RF deck causes the LO1 PLL to unlock. This points to a fault in one of the microwave components. The issue is traced to a broken solder joint inside of the VCO modules. After repair, the instrument functions normally. The performance and tracking generator functionality is verified by measuring a tuneable band-pass filter.
The Signal Path
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=1_M-Wccn2w8
In this episode, Shahriar presents the theory, design and characterization of Nyquist Digital to Analog Converters (DACs). After a brief overview of DAC operation and theory, the schematic of an 8-Bit R-2R DAC is presented. The R-2R DAC, which is driven by a dsPIC30F6014A Microchip microcontroller is capable of producing ramps and arbitrary waveforms uploaded through an RS232 interface. The static integral non-linearity (INL) and differential non-linearity (DNL) is measured by using a Rigol DM3068 Multimeter through a Matlab interface program. The dynamic performance of the DAC is characterized using an Analog Devices AD6645 105MSps 14-Bit ADC evaluation board coupled with a USB FIFO interface board. By using the 'Visual Analog' software, the spectrum of the DAC output as well as the signal to quantization and distortion ratio (SQNDR) is calculated. Finally, the impact of component mismatches, operational amplifier non-linearity and timing uncertainty on the INL/DNL and SQNDR (ENOB) of the DAC is examined.
...
https://www.youtube.com/watch?v=aDiCqgWWqDU
In this episode Shahriar reviews the Tektronix RSA607A real-time spectrum analyzer which operates from 9kHz to 7.5GHz. The instrument has a 40MHz wide analysis window with a DANL of -160dBm. The built-in tracking generator is capable of measuring return loss, cable loss and DTF measurements without a need for an external coupler. This review is organized as follows:
01:03 – Model comparison and overview.
03:25 – Front & rear panel overview.
05:31 – Complete unit teardown & examination.
16:33 – Reverse engineering and experiments with a drone remote control transmitter.
39:27 – Characterizing and experimenting with an ISM band diplexer.
47:29 – Return loss measurements of a tunable band-pass filter.
53:23 – Concluding remarks.
The Signal Path
www.TheSignalPath.com
www.YouTube.com/TheSignalPath
www.Patreon.com/TheSignalPath
...
https://www.youtube.com/watch?v=CFQxqZcWGHg
In this episode Shahriar repairs an Anritsu 37347A 20GHz Two-Port Network Analyzer. The unit does not boot up and as a result its internal state is unknown. The boot fault is traced to a bad RTC module which has a built-in integrated battery. A replacement unit is located which allows the unit to fully boot.
The instrument initially displays an unlock condition on the internal PLL. This problem is resolved by loading the PLL calibration files from the HDD. The complete block diagram of the unit is examined in detail and an unusual PLL intermittent locking problems is demonstrated. Various measurements on several of the internal PLLs confirm their functionality. As a final experiments, the instrument is calibrated and the S-parameters of a tune-able band-pass filter is measured.
The Signal Path Blog
http://www.TheSignalPath.com
...
https://www.youtube.com/watch?v=dwAieDTRMdQ
In this episode Shahriar reviews the Analog Discovery Pro 3000 Series, particular the ADP3450 model. The instrument offers a combination of mixed signal oscilloscope and dual-channel arbitrary waveform generator. The WaveForms free software can be used to perform a wide range of measurements. You can find more information about this product at:
https://digilent.com/shop/analog-discovery-pro-3000-series-portable-high-resolution-mixed-signal-oscilloscopes/
The review is organized at follows:
00:00 - Introductions
00:35 - Instrument overview, functions, specifications and design
04:53 - Detailed teardown and architecture overview
11:17 - WaveForms software, oscilloscope capabilities, catching glitches, trigger functions
19:18 - Mixed-Signal measurements, logic analyzer, cross-domain triggering
22:19 - Serial decode, digital trigger, correlated measurements
24:03 - Waveform generation, synchronized signals, modulations, sweeps, FFT, 3D spectrogram
28:46 - Network analyzer functionality, measuring linearity and frequency response of DUT
33:42 - Impedance analyzer functionality, measuring complex impedance across frequency
36:29 - Additional capabilities, tracer, scripting, etc.
37:39 - Concluding remarks
...
https://www.youtube.com/watch?v=ryxxYGmRCpQ