Archive for Shahriar

Teardown, Repair & Experiments with an Agilent N4901B 13.5Gb/s Bit Error Rate Tester BERT

In this episode Shahriar repairs a non-functional N4901B 13.5Gb/s BERT mainframe. This instrument is equipped with both the generator and analyzer modules which makes it fairly valuable. The instrument does not power on and does not react to the soft power button.

Teardown of the unit reveals a TD-Lambda Vega power supplies series which is a fully configurable switching power supply design. Even though the power supply in the instrument is completely custom, it is made from generic sub-blocks readily available on eBay. A replacement front-end is purchased to repair the power supply after detecting the problem.

The instrument also shows a minor problem with falsely detecting an overload condition on the delay control port which is by passed by installing an overwrite switch. The instrument performance is verified by generating and measuring various eye diagrams through a back-plane PCB board.

Tektronix 5-Series 8-Channel 6.25GS/s 2GHz MSO Teardown & Spectrum View Experiments

In this episode Shahriar continues his review of the Tektronix 5-Series 8-Channel MSO Oscilloscope following the original overview of the instrument. A full teardown of the instrument as well as a set of experiments showcasing the new Spectrum View capability are shown. This review is organized as follows:

00:09 – Introduction and outline
01:31 – Teardown and analysis of the acquisition board
13:38 – Experiment setup and description
16:59 – Measurement results and Spectrum View capabilities
33:12 – Concluding remarks

Teardown, Repair & Experiments with an EG&G Instruments 7265 DSP-Based Lock-In Amplifier

In this episode Shahriar takes a close look at an EG&G DSP-Based Lock-In Amplifier. This instrument provides excellent sensitivity for both voltage and current inputs and is based on a fully digital architecture. The instrument’s LCD screen is dim and unreadable. Furthermore, a few lines are missing from the LCD pointing to a failed zebra strip.

The instrument’s block diagram is examined and explained. The teardown reveals the structure of the LCD screen, front-end blocks and internal PLL. The CCFL back-light inverter is located and replaced with a low-voltage DC-DC converter for use with an LED strip. The instrument’s functionality is verified through a few experiments including measuring the 3dB bandwidth of an RC filter as well as measuring the photo-current induced in an LED using a synchronized infrared light source.

Teardown, Analysis & Repair of an Agilent E3646A Dual Channel Programmable Power Supply

In this episode Shahriar investigates a malfunctioning E3646A Dual Channel Programmable Power Supply. The power supply provides the correct output voltage on one channel. However, the second channel produces no output and continuously reads 0V and 0A.

Applying an external voltage to the malfunctioning channel produces the correct readout from the instrument display suggesting that most of the channel circuitry is functional. After a close examination of the power supply schematics, the problem is traced to a failed solder joint. The DAC output amplifier is disconnected from the output transistor and after repairing the colder joint, the power supply is fully functional.

Sindoh 3DWOX 1 Review, Experiments & 3D Microwave Component Printing Techniques

In this episode Shahriar reviews his new 3D Printer Sindoh 3DWOX 1. This printer offers several attractive features. The fully enclosed design is quiet and equipped with a HEPA filter. The unit is also equipped with a webcam and internal lighting. The printer has several automatic capabilities such as auto filament load from a cartridge, bed-leveling and print parameter optimization. The printer is also completely compatible with off-the-shelf filaments.

This comprehensive review is organized as follows:

01:57 – Model comparison and Sindoh website
02:26 – Printer design and overview
04:16 – Internal construction and features
07:03 – Cartridge design and filament auto-load
09:31 – Printing bed auto-leveling procedure
11:53 – 3DWOX desktop software overview and features
16:32 – First print example and procedure
17:53 – Mobile app and remote camera monitoring capability
18:51 – Print example: Objects with extreme aspect ratios
22:03 – Print example: Objects with moving parts and joints
25:27 – Print example: Objects with many holes and thin features
28:24 – Print example: Large objects with >24 hour print time
30:12 – Analyzing internal print features using an X-ray machine
32:46 – Printing microwave and mm-wave components and filters
38:27 – Concluding remarks

You can purchase a 3DWOX 1 printer from here or visit the manufacturer’s website for more information.

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