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Category: Test Equipment


Hickok 209A VTVM Restoration Part 6

Posted by Shaun Merrigan in Electronics, Restoration, Tech, Test Equipment. No Comments

13th January

This is the sixth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254.

Hickok 209A VTVM Restoration Part 6: Component replacement decisions

In this Part 6 of the series I will document the condition of the passive circuit components in the Hickok 209A VTVM, and justify why I decided to replace (or not replace) them.

Initial resistor and capacitor measurements Hickok 209A

Starting with the resistors, I measured 8 initially, and of those 5 were out of marked specification on the high side. One more was right at the high side specification and two were within specification. These were all 5% and 10% tolerance carbon composition resistors. Based on these data, I made the decision to replace all the 5% and 10% carbon composition resistors. I used 1% metal oxide resistors with … Read More »


Hickok 209A VTVM Restoration Part 5

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on Hickok 209A VTVM Restoration Part 5

1st January

This the fifth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 5: Checking the meter movement.

This piece of test gear is all about the large, beautiful meter movement, so I need to determine if this one works properly. What I intend to do is connect the meter to a precision power supply and good ammeter through a current limiting resistor and then determine how the meter responds. The meter is supposed to be a 500uA full scale movement.

Here is the test setup:

Analog Meter Test Instrumentation Setup

A 10kohm limiting resistor is connected in series with the power supply. The power supply is a Tektronix PS5004 and the meter is a Tektronix DM5120.

Full Scale Deflection on the meter was about 497 uA:

Analog … Read More »


Hickok 209A VTVM Restoration Part 4

Posted by Shaun Merrigan in Electronics, Restoration, Test Equipment. Comments Off on Hickok 209A VTVM Restoration Part 4

1st January

This the fourth part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 4: Restoring the battery holder.

In Part 3 of this series I documented the condition of the D Cell battery holder and outlined the restoration plan for the unit. The first step is to remove and restore the corroded battery holder.

Hickok 209A SN 133254 Corroded Battery Holder

Besides the obvious corrosion, the white connecting wire to the negative terminal was corroded under the insulation from the battery spring clip to the switch solder lug. I replaced the entire length of this wire. The other short wire and ring terminal were cleaned as described below.

Hickok 209A SN 133254 Corroded Terminal Wire

The process I used to restore the battery holder:

Desolder the two … Read More »


Hickok 209A VTVM Restoration Part 3

Posted by Shaun Merrigan in Electronics, Test Equipment. 1 Comment

1st January

This the third part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 3, corrosion issues and restoration plan.

As mentioned in Part 2 of this series, a visual inspection of the chassis of the 209A revealed a serious corrosion problem with the battery holder. The corrosion had migrated to the bottom of the case but not to the remaineder of the chassis. There were no batteries in the unit when I received it.

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

Hickok 209A SN 1333254 Battery Holder Corrosion

From the above images, it is clear that the battery holder will require some corrosion mitigation and restoration. Fortunately, it is restorable as the parts are … Read More »


Hickok 209A VTVM Restoration Part 2

Posted by Shaun Merrigan in Electronics, Test Equipment. 1 Comment

1st January

This the second part of an “N” part series documenting my restoration of the Hickok 209A VTVM, SN 1333254. Hickok 209A VTVM Restoration Part 2, visual inspection.

Outside visual inspection results:

Overall good visual condition outsideMeter appears to move freely and does not stickMeter face is excellent and there are no scratches on the glassMeter bezel is dirty, but does not appear to be corrodedArea of corrosion noted at bottom of caseThe case has some minor paint scuffs and nicks accumulated over the past 60 yearsLine cord appears to be original and looks to be in good conditionHas an original rubber grommet where the line cord enters the caseNo obviously broken parts: lamp, pin sockets, dials are in good conditionHas DC Probe (reads 3.36 Mohms)No AC probe but does have the 4 wire AC probe connectorNo pin tip test … Read More »


Hickok 209A VTVM Restoration Part 1

Posted by Shaun Merrigan in Electronics, Test Equipment. Comments Off on Hickok 209A VTVM Restoration Part 1

31st December

This is the first installment in a multi-part series documenting my restoration of a classic Hickok 209A VTVM. First a description and some images:

This is a Vacuum Tube VoltMeter (VTVM) with a nominal 12 Mohm input impedance and one of the largest mechanical meter movements found on commerical/consumer equipment (viewing area about 8.5 inches diagonal). It was produced from about 1947 (earliest direct evidence) to at least 1961 (catalog reference). One of the units I have has 03-09-55 written in grease pencil on the back of the meter movement. The cost in 1947 was (reportedly) $133 USD which is about $1500 USD in late 2018. In comparison, the HP 410A (a lab grade instrument) sold for $245 USD in 1948 or about $2500 USD in late 2016 dollars. So the Hickok 209A was not aimed at the laboratory … Read More »


HP 1340A Display Repair -2

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Test Equipment, Troubleshooting. Comments Off on HP 1340A Display Repair -2

29th December

HP 1340A Display Repair


HP 1340A Display Repair – 1

28th December

I purchased a couple of HP 1340A XYZ Displays which I thought would be useful as troubleshooting aids and as graphical displays of CRT technology (oscilloscope clocks, and the like). Upon receiving them, they both worked, but careful visual inspection showed some potentially serious problems. I will document the repair process here.

HP 1340A Overview

HP 1340A Overview

HP 1340A Overview

HP 1340A Overview

HP 1340A Overview

HP 1340A Rear Panel, High Serial Number

Visual inspection of the units revealed the following problems:

Heat damaged A1R81 (both units)Heat damaged A2R13 (both units)Loose mounting hardware and corroded wiring on A2Q2 (one unit)

Heat Damaged Components

LVPS A2Q2 Damage

Heat Damaged Components

A2Q2 is mounted directly to the case for heatsink purposes. The hardware was loose, therefore the transistor effectively had no heatsink. I suspect that it had been running hot for quite some time because the PVC insulation … Read More »


HP 3562A CRT Replacement

Posted by Shaun Merrigan in Electronics, Oscilloscopes, Test Equipment. Comments Off on HP 3562A CRT Replacement

28th December

Based on my own observations and reading, the CRT in the HP 3562A is a marvelous piece of engineering. However, it literally fatigues over time and at some point the deterioration cannot be compensated for by the range of adjustments. The solution is to replace the ageing CRT display with a modern LCD. It turns out that SimmConn Labs has such a kit:

http://www.simmconnlabs.com/1401/2501.html

Terry at D-Lab Electronics did a good video on how to replace the original CRT with the LCD Kit from NewScope:

https://youtu.be/WKz7GYBON7g

Terry does a great job of documenting the replacement process, so I will focus on the before/after results. I will start with original CRT images, followed by LCD images and by split screen comparison images. Since I also purchased the RGB to VGA adapter cable from SimmConn, I will conclude with an … Read More »


600 Ohm Terminator Build

Posted by Shaun Merrigan in Audio, Electronics, Test Equipment. Comments Off on 600 Ohm Terminator Build

27th December

When doing work on older audio gear it is sometimes necessary to maintain a 600 ohm impedance from, for example, a signal generator to a DUT or a piece of test gear. An easy way to do this is with a 600 ohm terminator. The article will document how I built such a terminator.

First I want to acknowledge the work of ElPaso TubeAmps (David Beard) who covered this very subject several years ago:

https://youtu.be/tIB3U-U29wg

50 ohm and 75 ohm BNC terminators are relatively easy to obtain, but 600 ohm terminators harder to come by. The solution is to build one as follows:

Obtain a suitable 50 or 75 ohm BNC terminator . You need the type which can be opened. One clue is that it may have flats on the end of the barrel which were used during assembly.The … Read More »