Shaun Merrigan's Information Pages

Tag: Electronics Repair

Tektronix SG5010 Audio Signal Generator Repair

Posted by Shaun Merrigan in Audio, Electronics, Test Equipment. Comments Off on Tektronix SG5010 Audio Signal Generator Repair

14th December


The Tektronix SG5010 is an audio signal generator plug-in for the TM5000 modular test equipment system. It can generate five waveforms: sine wave, square wave, SMPTE/DIN intermodulation test signal, CCIF intermodulation test signal, and sine wave burst. All these signals may be swept in frequency and amplitude. It can generate very low distortion (THD+N < 0.0008%; my own measurements) sine waves from 20Hz-20kHz. It is CPU controlled with selections made via GPIB or front panel keyboard. These characteristics made it very desirable as part of an audio amplifier test lab. These units command a high price: Several working units have recently (Dec 2023) been sold for $USD 1500.

I recently acquired a non-working SG5010 for a good price. This post documents my efforts (ultimately successful) in getting it working.

Tektronix SG5010 Overview

Tektronix SG5010 Front Panel

First … Read More »

Tektronix 284 Pulse Generator Repair

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on Tektronix 284 Pulse Generator Repair

21st November

This post will document my recent repair of a Tektronix 284 Pulse Generator. This device was introduced by Tektronix in 1967. It can produce:

A 50kHz, 200mv fast risetime pulse. Typically, tr < 70 ps

A 100 kHz, 1 MHz, or 10 MHz square wave at 10, 100, or 1000 mV

A 100 MHz or 1 GHz sine wave at 100 mV

The Tektronix 284 can be used to check the risetime of oscilloscopes, (both sampling and real time) amplifiers, transistors, transient responses, and for TDR work. The pulses are generated by a tunnel diode which is a semiconductor device capable of changing states very quickly. Tunnel diodes were invented in the late 1950’s in Japan and widely used in test equipment through the 1970’s. Tektronix used tunnel diodes in “pulsers” like the 284 and many oscilloscopes including the … Read More »

HP Z3200 Belt Tensioner Repair

Posted by Shaun Merrigan in Photographic Printing, Tech. Comments Off on HP Z3200 Belt Tensioner Repair

22nd August

During a recent printing session, my Z3200 declared an “86:01 paper jam” error. Looking into the printer, I quickly realized that the carriage belt had gone slack. I replaced the OEM carriage belt a number of years ago with a very high-quality belt from LPS Computer, so I was quite sure the belt had not broken. A quick examination of the carriage belt path revealed that the belt tensioner had failed. More specifically, the shaft which holds the pulley had failed.

Belt Tensioner Pulley Failure

What to do? Obviously order a replacement part, but it would take several days to arrive, and my printer would be unavailable in the interim. So, I decided to repair the broken shaft. Past experience suggested that merely gluing the shaft back together would not work. I believe the shaft is ABS … Read More »

Tektronix Type 114 Pulse Generator Repair

Posted by Shaun Merrigan in Electronics, Restoration, Tech, Test Equipment. Comments Off on Tektronix Type 114 Pulse Generator Repair

22nd May

I recently completed repairing/refreshing and calibrating two Tektronix Type 114 Pulse Generators. This is a solid state pulse generator with variable pulse width (100ns – 10ms) and period (1us to 100mS). It can produce pulses of both polarities (-10v to +10v into 50 ohms). It was introduced in 1965. The two examples I obtained were SN 001791 and SN 003460. Initally, both units were produced output, but the waveforms were distorted (rounded square waves) and far out of specification in terms of period, pulse width, and risetime.

Tektronix Type 114 SN 003460 Front Panel

Tektronix Type 114 SN 003460 Overview

Tektronix Type 114 Pulse Generator SN 001791 Front Panel

Visual inspection also revealed damaged components and mechanical damage. A summary of the issues found follows:

Pulse width and period were out of specificationNegative pulses and square waves were … Read More »

HP 3245A Capacitor Replacement

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on HP 3245A Capacitor Replacement

4th January

The HP3245A Universal Source (datasheet is copyright HP/Agilent) is a precision AC/DC voltage and current source that can provide a wide range of precise and repeatable voltages and currents up to +-100vdc and 100mA dc. It can also provide sine, square and arbitrary waveforms up to 1Mhz and 200vpp. Such an instrument is extremely useful in the lab for calibrating meters, driving current and voltage amplifiers and checking equipment. The particular units I have were built in 1992/1993 which means the electrolytic capacitors are approaching 30 years of age. I had decided to replace the RIFA line filter capacitors in (documented here) both my units and performed routine power rail voltage and ripple checking as part of that. For example:

+5.0840 4.4mv+15.194 30mV+18.625 29mV-18.691 28mV

The other power rails and HV Amp power supply also measured good, using an … Read More »

BK Precision 879B LCR Meter Repair

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on BK Precision 879B LCR Meter Repair

3rd January

The BK Precision 879B is a good quality, dual display 40,000 count LCR (inductance, capacitance, resistance) meter with 0.1% basic accuracy. It was first manufactured in 2010 and is still available (2021) for around $420 Cdn. I purchased mine several years ago and find it very convenient and easy to use.

BK Precision 879B

Things I like about the 879B:

Open/short calibration completes very quickly as opposed to the DE 5000Decent quality Kelvin clips and smd tweezers40,000 counts for extra accuracyVery good accuracy when compared to my HP4263ALong battery lifeEasy to use menu system and quick setup

A common problem with these units is the lack of robust input protection. What this means is that if you forget to discharge a sufficiently large capacitor and attempt to test it, you will damage the front end of the meter which will … Read More »

HP 3562A ROM Repair

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on HP 3562A ROM Repair

26th December

Early in 2018, I purchased an HP 3562A Dynamic Signal Analyzer for an excellent price on Ebay. The display looked great and it was physically in good condition. However, the unit failed the power on self test as follows:

HP 3562A Error Message on boot

This error code indicates a ROM IC failure.

HP3562A Diagnostic LED’s indicate Hex code 4 4 (0100 0100)

This code indicates a failure of ROM Chip U105:

HP 3562A Rev B ROM board. The problem ROM chip is the fifth chip down in first column (U105)

HP 3562A ROM Board Rev B

This ROM board is an older version using 32kx8 chips in two groups (Low Byte & High Byte) of 18 chips each. I had access to a second 3562A, and swapping ROM boards confirmed that the ROM board was the problem. Now I needed to:

Locate a suitable set … Read More »