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In this episode Shahriar repairs a faulty Agilent 3458A. These highly desirable multimeters have continued to climb in price in the past few years. The last time The Signal Path has repaired one of these units was back in 2018.
This instrument generates several errors both during power up as well as Auto Cal procedure. The error points to a failure in the OHMS measurement mode. Detailed instrument block diagram and schematics are examined. Measurements also show incorrect DC current sourcing during OHMS measurements and the associated circuits are closely analyzed. The problem is traced to a quad-comparator IC. Replacement corrects all problems during ACAL. The battery backup of the SRAM ICs are also replaced to eliminate non-volatile errors. The IC of the comparator chip is also extracted and examined under the microscope.
The repaired instrument performance is verified by using voltage, current and resistance standards.
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In this episode Shahriar repairs an Agilent N9912A which flags several error messages after bootup. The instrument reports hardware time-outs and occasionally ADC clock source unlock condition. The second error is much more useful in debugging the unit.
The block diagram of the instrument is presented and several potential failures anticipated.
The teardown of the unit and analysis is also presented. After some troubleshooting, it becomes clear that the primary 30MHz TCXO has a broken internal connection. The unit is disassembled and new pins installed. After putting the TCXO back into the unit, the instrument return to full functionality. A few quick experiments verify that the FieldFox performs both CAT and SA modes correctly.
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In this episode Shahriar shows an extensive review of the Sanko (BirdRF) GH60 GeneHawk handheld vector signal generator which operates from 10MHz – 6GHz. With up to 100MHz of modulation bandwidth (licensed) the unit has good potential for a portable wide-band communication signal generator:
https://www.sankorf.com/products/portable-signal-generator-gh60
This review is organized as follows:
00:00 – Introductions, unit overview, operating system & GUI initial impressions
02:33 – Detailed teardown, construction, RF & baseband board analysis
19:16 – Frequency accuracy and stability measurements
20:31 – Output power measurement, power linearity and minimum output power
24:28 – CW signal analysis, noise-floor, harmonic behavior and spurious tones
27:15 – Phase noise characterization, spurs and far-out noise floor
28:41 – Two-tone generator, TOI (OIP3), image rejection, LO rejection, intermodulation tones
31:13 – Pulse generation, minimum pulse behavior
33:36 – Linear frequency generation measurements & characteristics
34:58 – FM, AM & PM capabilities and characterization methods, multi-modulation options
37:22 – Frequency sweep behavior and limitations
40:07 – Custom digital modulation, EVM measurements, I/Q & magnitude error, equalization
43:05 – Real-time AWGN performance and measurements
44:00 – Other software features, up-coming API and waveform standards
44:44 – Concluding remarks
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In this episode Shahriar takes a look at a faulty dry block calibrator from Ametek. These Jofra series temperature calibrators are widely used for thermostat validation as well as material analysis. This particular unit does not cool down or warm up but seems otherwise functional.
A brief set of measurements shows that one of the Peltier elements is damaged and should be replaced. A replacement is located and the temperature well is re-sealed. The unit is functional and the minimum temperature performance is verified.
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