Bill Cohron - About Hickok Tube Testers

Bill Cohron

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When you have Vacuum Tube Tube equipment...

Having Vacuum Tube equipment is just fun. Working with technology that is more than 100 years old but still perfectly functional and is, in many cases, even preferred over the more modern equipment, is very exciting. Of course, it also presents a unique set of challenges.

In order to have reliable Vacuum Tube equipment, you have to be able to maintain it. This fact ended up leading me down another rabbit hole... Vacuum Tube *Test* Equipment! LOL

Vacuum Tubes and a brief Hickok history

As I started becoming more and more interested in Vacuum Tube equipment... amplifiers, stereos, HAM radio equipment, and the like... I began to realize that if I was going to be able to keep this equipment functional, I was going to need a way to be able to test the tubes as needed. Unfortunately, this is not nearly as easy as it sounds.

When I was a kid growing up in the '70s and '80s, vacuum tube electronics were still quite popular. TVs and Stereos made up a large part of this equipment, and nearly every drug store and hardware store had a vacuum tube test stand in the corner where you could test any suspect tubes.

Sadly, time marches on and test stations have long since disappeared from the American landscape.

This doesn't mean that the tube community is out of luck. Actually, far from it. Nearly as long as there have been vacuum tubes, there have been repairmen who would come to your home or business and repair your equipment. It is clearly not feasible to transport vacuum tubes back and forth to a facility to test them, so many electronics companies started making portable vacuum tube test equipment.

One of these companies was Hickok, Inc. If you are interested, you can download a PDF containing a more detailed history of the company here: Hickok History

On may 14, 1910, Robert D. Hickok began the Hickok Electical Instrument Co. in a small building behind his home in Atlanta, GA. The company initially began by building panel instrumentation for switchboards and other equipment. Moving from Atlanta to Cleveland, OH in 1913, the company expanded its line to include instruments for the Navy. This lasted through the First World War.

The early 1900's was awash with experimentation in radio, and the vacuum tube was a major part of the progress in radio development. After the war, Mr. Hickok was very interested in radio and while building his own elaborate receiver, he realized that there was a need for a device that could easily test vacuum tubes. With the invention of the B-47 Tube Tester around 1920, Hickok Electrical Instruments, Co. was firmly in the vacuum tube testing equipment business.

Over the next 50 years, tube testing equipment would follow along the many advancements made in vaccum tube technology, and Hickok Electrical Instruments, Co., now known as Hickok, Inc., was right at the forefront of this continually developing technology. With well over 100 different types of test equipment, vacuum tube testers were a huge part of the company's test equipment product line until they were discontinued sometime in the mid-'70s.

100 years later, Hickok tube test equipment is still highly regarded and highly sought after by collectors of vintage vacuum tube equipment. With the bulk of the test equipment being manufactured from the '50s to the '70s, these devices are still very reliable and can often be found reasonably priced. Well, about as reasonable as anything else in the vacuum tube world anyway.

So, with that little bit of history of Mr. Hickok and his company, I will now take you on a virtual tour of my collection of vintage Hickok vacuum tube testing equipment. Enjoy!

My Hickok Vacuum Tube Test Equipment

In order to be able to keep my equipment running efficiently and effectively, I was going to need to be able to test the tubes from time to time. After weeks of research, I finally decided that the Hickok testers were going to best fit my needs as well as my budget. Yes, there are some really nice testers still available, and some of these are more thorough in their testing methods and results. However, these features come with a price and since I'm not in the business of buying and reselling vacuum tubes, I really don't need those extra features. So, off to eBay with gusto I went!

Hickok 600A - Unit #1

This is my first Hickok unit. It is a model 600A and came to me working perfectly. Of course, as soon as I received it I tore it down to get a more thorough understanding of how it worked. The amount of documentation available on these devices plentiful, with full schematics and service manuals to help make sure that these unit are the best possible state of calibration. I use this one often and it still continues to impress me with how well it works and how easy it is to use, despite the fact that it's more than 60 years old.

Hickok 600A - Unit #2

With how my mind works, my thought process was that eventually I might need a backup unit just in case my first unit should fail. I mean, the units have rectifier tubes in them and if they go out, how am I going to test them without another unit as a spare. At least it made sense in my head. LOL So, back to ebay I go looking fo another unit at a reasonable price.

I came across one and the description indicated it was from an estate sale and that the unit had only been used twice. After looking at the picture, I had no reaosn to believe otherwise. This unit looked flawless! I bid on it and ended up winning the bid at an extremely reasonable price... Even better than my first unit. Now to wait for it to arrive from Canada!

The unit arrived and I was in shock. When I tell you this unit is flawless, I mean it is FLAWLESS! It literally looks like it just came from the factory yesterday and is an absolutely stunning example of one of these devices. I did go through the device and make sure that the tubes were good, that the sockets were clean, and everything otherwise worked. Now, I certainly can't use this unit because it simply is just too nice to put into service. So I have it carefully packaged and will hold on to it until such time as I either need to use it or I can pass it along to someone who can appreciate it as much as I do.

Hickok 800 - Unit #3

Since my second unit was relegated to the archives, I still needed to find a functional spare unit. I gave eBay another spin and very quickly found a really nice deal on a Hickok 800 tester. The auction finished and when my unit arrived, I was quite surprised. Usually, when you get stuff from eBay, there's no history or anything that comes with the item. You get what you get and have a nice day. Well, not with this item.

Upon opening the package and inspecting the device, I was pleased to find that all the original documentation including the original invoice was saved. This unit was purchased in 1962 by Mr. Andrew Twyman of West Virgina, and the vacuum tube data scroll was updated to the 1968 version in March of 1969.

After doing a bit more research, I learned that Mr. Twyman was born in 1935 and worked as an Iron Worker from 1951 to until 1969 when he was elected as the Financial Secretary of the Iron Workers Local 787 in WV. Sometime in 1960 or 1961, he had gone to a trade school to learn electronics and TV repair and then opened his own repair shop, Andy's TV Service and Repair. It's unclear when, but he eventually sold the business and returned to Iron Working and was involved in that industry until he retired in 1990 in the house he built in 1957.

It's stories like this that I find fascinating. To learn about the history of someone... something... somewhere... It makes these adventures worthwhile. Anyway, here's unit 3 in all its glory.

Hickok 539C - Unit #4

The Hickok 539C is a much more robust and a much more precise vacuum tube tester. This is considered by many to be the Cadillac of the Hickok vacuum tube test equipment. As they say, "With great power comes great responsibility" and that cetainly applies to this unit. Where the other units are simple to operate and are great for identifying weak tubes or simple output matching for sets, this unit allows for more in-depth testing at the cost of a slightly increased complexity in operating the unit.

This unit was purchased directly through Hickok Meters and had a few modifications to allow for external voltmeter attachments for increased accuracy in testing. I mostly use this unit when I want to very closely match audio signal tubes so that there is little variation between left and right channels. It is an absolutely wonderful unit and is also one of the gems in my collection. I hope you enjoy these images.

Hickok 533A/600A/605A/800/800A/6000A - Test & Repair Stand

In the process of learning about these wonderful devices, I found that it was extremely clumsy trying to do any testing or calibration of the unit once the panels were removed from the cases. Trying to connect leads, hold a voltmeter, and push buttons for testing... All while not trying to ELECTROCUTE myself... proved to be an extremely precarious task. I ended up build this very handy test stand so that I could position the panel in any orientation I needed in order to proper test and calibrate my units. It works extremely well and I have included the drawings below in case you'd like to build your own.

In conclusion...

This is my current collection of test equipment. I hope that you might have learned something new and would be pleased to know if you find these devices as fascinating as I do.

As my journey through this hobby progresses, I may acquire other units or may sell off ones that I already have. I will be sure to update this page as these changes occur.

If you happen to have any questions about these devices, how they work, or where you can find parts and/or documentation, please feel free to reach out to me and I'll be happy to assist as best as I can.

You can reach me here: Contact The Cohrons

Take care and God bless!


All contents Copyright 2024 The Cohron Family and William Cohron