Tag Archive for Analog

Teardown, Repair & Upgrade of an Agilent 3458A 8.5 Digit Digital Multimeter

In this episode Shahriar repairs and upgrades an Agilent 3458A 8.5 Digit Multimeter. The instrument has been kindly donated by AllTest Instruments Inc. You can access their website here, as well as their eBay store, Bonanza store and TestUnlimited hub. AllTest provides the following:

  • Massive inventory of test and measurement equipment with over 20,000 units to chose from.
  • Full service general laboratory where repairs, refurbishment, and testing are carried out.
  • An additional NIST traceable metrology laboratory with extensive T&M capabilities where OEM grade calibrations are performed.
  • 5% discount on any purchase when The Signal Path Blog is mentioned for first time customers with limit one per customer.

The 3458A unit fails startup conditions with several errors. After close inspection of the boards, the initial problem points to a poorly plugged in fiber-optic cable. After this fix, the unit still fails ACAL on the AC Board. The unit’s NVRAM modules all have to be replaced. During this process the memory of the unit is also upgraded and the firmware is updated to the latest available version. After analysis of the schematics the problem is traced to a damaged JFET input operational amplifier on the attenuator flatness calibrator unit. The replacement allows the unit to pass all self-test and ACAL calibration. The instrument is then NIST calibrated by AllTest Instruments and shows excellent performance when compared with various multimeters in the lab.

Rohde & Schwarz RTB2004 10-Bit, 2.5GS/s MSO Oscilloscope Review, Teardown & Experiments

In this episode Shahriar reviews the Rohde & Shwarz RTB2004 10-Bit oscilloscope. With its high-resolution touch-screen, intuitive and capable GUI as well as excellent analog/digital performance this scope competes very well against other 2000 series instruments from Tektronix and Keysight. This extensive review includes instrument teardown, overview and dedicated experiments as follows:

01:17 – Model comparison and R&S scope lineup.
02:20 – Front panel, rear panel and overview.
05:01 – Instrument teardown and analysis.
13:37 – Power on and basic functions including intensity grading, XY mode.
26:29 – Multi-tone behavior, FFT and ADC performance.
33:17 – Experiment with ambient light follower: Analog and RS232 digital serial capture, triggering and analysis.
48:03 – Experiment with external DAC: Analog and I2C data capture and search using remote web interface.
57:19 – Built-in arbitrary waveform generator behavior and performance.

Dino-Lite USB Digital Microscopes Review and Experiments (2017 Edition)

In this episode Shahriar demonstrates a series of new Dino-Lite USB Digital Microscopes released in 2017. Several models are shown:

  • AM7515MT8A – This unit offers 700X-950X magnification with built in coaxial lighting as we as switchable bright-field and dark-field lighting options.
  • AM73915MZT – USB 3.0 interface with one touch auto-focus, EDOF & AMR. The unit also offers up to 45FPS in lower resolution mode. The magnification range is 20X – 220X.
  • AM73115MTF – USB 3.0 with Dino-Lite’s longest working distance at 1X – 70X magnification. Capable of 20X at 10.5” working distance and 70X at 4.5” working distance.
  • AM5218MZT – HDMI/DVI output connections, new edge optics, minimal latency with fast frame rate up to 60FPS in good lighting conditions.

Furthermore the Vision M1 automated platform is also presented which can be used to manipulate the XYZ position of any microscope through a PC USB connection. All other presented accessories can be found on Dino-Lite website.

The above models are used to analyze several microwave amplifier modules and components. The ASIC die of a 30GS/s Track & Hold Amplifier (THA) as well an RGB light sensors are also closely examined.


Noise & Performance Considerations of the DPH3205 Buck-Boost DC/DC Converter Module

In this episode Shahriar investigates the noise generated from the DPH3205 Buck-Boost DC/DC Converter Module. This module is part of a family of affordable devices which can be purchased online. The particular model (DPH3205) shown in this video can be purchased from here. The Keysight S-Scope in conjunction with the N7020 power probe is used to measure the noise behavior of the circuit. It can be observed that the module produces many harmonics of noise spanning up to and beyond 1MHz.

A power operational amplifier is used in conjunction with a 4V Zener diode to produce a crude voltage follower. The PSRR of the operational amplifier can filter the noise from the DC/DC converter. This is verified by measuring the noise coming from the operational amplifier. The noise is significantly reduced. This circuit is not entirely practical and is used for demonstration purposes only.

Teardown & Repair of an Agilent E3632A DC Power Supply

In this episode Shahriar & Rosanah investigate an Agilent power supply which does not appear to power on. It can be quickly observed that the fuse has failed on the unit. Using an isolation transformer a small amount of AC voltage is applied to the unit after the fuse replacement. It is clear that a short is present somewhere in the instrument since even at 10V AC the instrument consumes more than 1A.

After separating the internal transformer from the main PCB, the high current consumption is eliminated. The short is traced to a damaged main rectifier in the instrument. A replacement rectifier is used which allows the instrument to power on.

The VFD display is however extremely dim. After a failed attempt at restoring the VFD brightness, a new display is purchased from eBay. The replacement produces a bright vibrant VFD display. The performance of the power supply is verified under load.

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