Shaun Merrigan's Information Pages


Category: Test Equipment


Tektronix TM500 Power Frame Tester

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on Tektronix TM500 Power Frame Tester

25th June

The Tektronix TM50n is an “n”bay (where n = 1 to 6, the number of bays) power frame which can host and power TM500 plug-ins. It was available in 1 through 6 bay versions and was the predecessor to the TM5000 power frame: See my post here about the TM5000 power frames. Tektronix themselves had dozens of plug-ins available which comprised power supplies, signal generators, oscilloscopes, multimeters, test oscillators, calibrators, attenuators, filters, logic analyzers, frequency counters, audio analyzers and more. It is important to note that while TM500 plug-ins can be used in the TM5000 power frame, the inverse is not true: TM5000 plug-ins cannot be used in a TM500 power frame.

Part of the repair/refresh process of any TM500 power frame requires the use of a Power Module Tester which (in conjunction with some basic test equipment … Read More »



Tektronix Type 106 Square Wave Generator Refresh

Posted by Shaun Merrigan in Electronics, Restoration, Tech, Test Equipment. Comments Off on Tektronix Type 106 Square Wave Generator Refresh

20th June

Introduced in 1966, the Tektronix 106 Square Wave Generator is a signal generator which can produce fast rise (<1nS @50 ohm loads positive or negative going) or high amplitude (120 Volts, high impedance load) square waves from 10Hz to 1MHz. It is used for oscilloscope calibration, risetime testing and for triggering extremely fast rise (<100pS) tunnel diode pulsers. The 106 uses a combination of vacuum tube and discrete solid-state technology. This is the sort of equipment that was used for development and testing during the NASA Apollo Program through the 1960’s.

The cost of the Tektronix Type 106 was USD 590 in 1966 or about USD 4900 in 2021 dollars. I was fortunate enough to obtain one of these units in decent condition and I was able to restore it to better than factory specification. What … Read More »


Tektronix TM5006 Power Frame Refresh

Posted by Shaun Merrigan in Electronics, Restoration, Tech, Test Equipment. Comments Off on Tektronix TM5006 Power Frame Refresh

17th June

The Tektronix TM5006 is a 6-Bay power frame which can host and power either TM5000 or TM500 plug-ins .

Tektronix themselves had about 130 different plug-ins available which comprised power supplies, signal generators, oscilloscopes, multimeters, test oscillators, calibrators, attenuators, filters, logic analyzers, frequency counters, audio analyzers and more. In addition, numerous third parties made plug-ins for the system. The total number of different plug-ins numbered at least 200. The system was introduced in 1972 and was available in some form through at least 1995. The system is remarkably interesting from a technology standpoint because it encompasses the move from discrete transistor circuitry in early equipment, evolving through microprocessor-controlled units in later equipment. The more modern TM5000 equipment also had network interface (GPIB) capability for control and data acquisition.

In terms of cost, a basic … Read More »


Tektronix Type 114 Pulse Generator Update

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

16th June

This is an update to my previous post documenting my restoration/repair of two Tektronix Type 114 Pulse Generators. As of this writing I have completed some cosmetic work on the cabinets, front panels and carrying handles of both units. This includes cleaning and painting the cases, cleaning the front panels, knobs, BNC connectors and replacing the missing handle inserts.

Tektronix 114 Handle Insert Bottom Section Missing

Tektronix 114 Handle Insert New Aluminum Base Plates and OEM Example

Tektronix 114 Replacement Inserts and Tolex

Tektronix 114 Replacement Handle Insert and Tolex in place

Tektronix Type 114 Refinished Cabinet and Front Panel

Tektronix 114 Front Panel Cosmetics Completed

I have implemented a Maintenance and Inventory system which includes an equipment label with QR code. The code includes the Equipment Name, Serial Number, Instrument ID Number, and a summary of the latest service work completed on the unit. … 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 »


RIFA Safety Capacitor Replacement in HP Gear

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on RIFA Safety Capacitor Replacement in HP Gear

3rd January

In a previous post, I had documented the condition of several RIFA Y Safety capacitors, showing clearly the cracked condition of the outer case. This condition is a precursor to the well documented failure of this style of RIFA capacitor. Reportedly, these problems have been solved since Kemet squired RIFA in 2007. Of course the equipment which contains these potentially failing capacitors is typically older than 2007.

For example, I recently replaced six (two from each instrument) of these capacitors from the following equipment:

HP 3245A (1992)HP3245A (1992)HP 3458A (1989)

HP 3245A (1992) Original RIFA Safety Capacitors. The line filter is on the bottom right.

HP 3458A (1989) Original RIFA Safety Capacitors. The line filter cutout is on the bottom right.

Each and every RIFA Safety Capacitor I removed from this equipment showed cracks in the case.

Cracked RIFA … Read More »


Hickok 209A VTVM Restoration Part 7

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on Hickok 209A VTVM Restoration Part 7

3rd January

I have completed the electrical restoration of one Hickok 209A VTVM. This included:

Replacing all the paper and electrolytic capacitorsReplacing all the carbon composition resistors (most were out of tolerance)Installing a polarized AC plug, line fuse and proper safety capacitorReplacing the meter movement (original was mechanically damaged)Rebuilding and restoring the battery holderBalancing the bridge tube resistorsGiving the unit a full check on all modes and ranges

With all of the above complete I can declare the unit ready to use. The cabinet still needs to be cleaned and refinished, but that will have to wait until warmer weather arrives and I can work outside.

The results of my testing were very interesting. I used my lab equipment (see below) to check the 209A on all of its ranges and modes (with the exception of the decibel range). … Read More »


RIFA Safety Capacitor Failures

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on RIFA Safety Capacitor Failures

13th November

RIFA Safety Capacitor Failures have been documented by many of us who restore and maintain vintage electronics equipment. One very spectacular failure was caught live here: courtesy Dave Jones of the EEVBLOG. These capacitors were widely used in test equipment manufactured during the late 1980’s through the 1990’s. The general consensus is that the capacitors fail because the outer case (presumed to be a type of epoxy) develops cracks which allows moisture to penetrate into the body of the capacitor. This leads to internal short circuits which cause the capacitor to fail catastrophically. Because these capacitors are line to ground, they could see line voltage whenever a piece of equipment is plugged in, even when switched off. The crack network can develop to the point where large pieces of the outer case spall off, exposing … Read More »