I recently found a February 1940 Jackson tube tester modernization bulletin. This bulletin explains the modernization options available for Jackson tube tester models 627, 627-C, 630, 633, 634, 634-C, 634-D, 635, 637, 680. It also includes the wiring diagram to install a Loctal socket into models 627, 630, 633, 635, 680.

Very interesting bulletin for anyone collecting or repairing vintage Jackson tube testers. I have scanned this 4-page document into a PDF for your benefit.

[ Download the Jackson 1940 Modernization Bulletin PDF ]

To summarize the bulletin:

• Models 634 and 637 sold in 1940 were already modernized at the factory
• Models 634 and 637 sold in their first year (1939) can be easily modernized by the owner (see my article on Jackson 634 for modernization data to install 9-pin miniature socket into these models).
• Models 627, 630, 633, 635, and 680 could be sent back to the Jackson factory and modernized for $5.00 (model 633) or $6.50 (models 627, 630, and 635, which dated from 1938), or $12.50 (model 680). All five of these models had to modernized at the factory because they required installation of a supplementary high-voltage filament transformer, among other parts.
• Models 427-A, 435-A, 535, and 580 were too obsolete to be modernized because “no provision for the high voltage filament types can be made. Miniature types cannot be tested.” Jackson noted that these models were “as much as five years old”, which dates them between 1935 and 1940. Jackson recommended upgrading to the new 1940 models of 634 and 637.

If you are only interested in the Loctal socket modernization wiring diagram, see the accompanying thumbnail photo (click photo to enlarge).

Loctal socket modernization

Going through my parts inventory, I found two nice Sencore Mighty Mite meters.

• Meter for TC-130 Mighty Mite III
• Meter for TC-136 Mighty Mite IV

Each is good condition, tested in-circuit and known to work good.

Price is $74 each plus Priority Mail (less than $5 to most USA destinations).

Email if interested. Again, these are meters - not the entire tester. If you need a replacement meter, this is your opportunity.

This article discusses repair and calibration of the older tube-based Sencore Mighty Mite tube testers that use the 12AU7A tube inside, such as model TC130, TC136, and TC142. I will also discuss the most common problem that causes “faulty” Grid Leakage detection. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

TC130 Mighty Mite

TC130 Mighty Mite case

Introduction

Sencore Mighty Mite testers employ a Cathode Emission test circuit, with short detection and industry-best 100-Megohm leakage detection. The leakage detection circuitry is really the reason that every technician should own a Mighty Mite as part of his/her tube testing arsenal.

All Mighty Mites are designed to test newer tubes. You will not find any antique sockets (such as 4-pin, 5-pin, 6-pin, 8-pin large, etc.) Socket configuration consists of Octal, 7-pin miniature, 9-pin miniature, Nuvistor, novar, Loctal, and Compactron.

Each model has a roman numeral designation: TC130 = Mighty Mite III. TC136 = Mighty Mite IV. TC142 = Mighty Mite V. There are no practical differences among them.

The older Sencore Mighty Mite tube testers have tube circuitry inside, whereas newer Mighty Mites (such as TC154 and TC162) are transistorized. Otherwise, their functionality is comparable. Some units have a CRT picture tube wire harness with socket attached. This harness is very bulky, so common sense would suggest to remove it. It serves no practical purpose and only clutters up the case. Some models have a few pin straighteners on the front panel.

(more…)

This article will discuss repair and calibration of the Heathkit TC-2 tube checker. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

A new SS9 socket saver has also been installed, and new Top Cap assembly has been installed.

(Heathkit TC-2 testing Arcturus Blue #127 detector tube)

Introduction

The Heathkit TC-2 was a self-assembled tube tester kit offered by the Heath Company. It was popular among servicemen because they could buy a “name-brand” tester and save money by building the kit themselves. Since the TC-2 is fundamentally the same as the Eico 625, Triplett 3413, and Knight 600/600A, which was the subject of my last repair-and-calibration article here on my website, I will not reiterate what was discussed in that article, and instead will focus on the minor differences between the TC-2 and the Knight 600. (Click HERE to read the previous article.)

Differences

The following minor differences exist between these models, and they need to be addressed when rebuilding and calibrating the TC-2:

(more…)

This article will discuss repair and calibration of the Knight 600 tube tester. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

(Knight 600 testing Sovtek 5881/6L6 audio tube)

Introduction

The Knight 600 series (600, 600A, 600B) was a self-assembled tube tester kit offered by Allied Radio Corporation. The copyright date of the Knight 600 manual is 1955. This tester, along with its brothers Eico 625, Triplett 3413, and Heathkit TC1/TC2, was popular among servicemen because they could buy a “name-brand” tester and save money by building the kit themselves.

(more…)

I have updated my article entitled “Rebuild & Calibration of Jackson 648A” to discuss how to eliminate the 1S5 tube from models 648 and 648A and upgrade to solid-state circuitry.

Newer versions of the “648″ (648R, 648S, etc…) use a solid-state circuit instead of a 1S5 tube. The benefit of the solid-state circuit is that the tester calibration should remain accurate much longer. If you do not mind checking your calibration on a regular basis, there is no need to perform this upgrade. It is more appropriate for power users.

Click HERE to jump to the article.

This article will discuss repair and calibration of the Jackson 561 tube tester. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

Also, the exact Jackson 561 that is the subject of this article is for sale [SOLD], rebuilt and calibrated as discussed below.

Introduction

The Jackson 561 appears to be a rare model. Very little documentation exists. In my 19 years in the hobby, I have only seen one other example. When I had the opportunity to buy this one, I jumped at the chance.

The model 561 is a combination of the Jackson 634 and the 648. Photo below shows Jackson 561 (left); Jackson 648A (right).

If the 634 and 648 mated, the 561 would be its offspring. It shares the following characteristics from the 648: (a) the same meter, (b) variable leakage control, (c) color scheme, and (d) case design. From the 634, it shares (a) the same test method (which Jackson calls “Dynamic Output”), (b) Shorts Test control, (c) lack of a Noise test, and (d) function control layout. In fact, the 634 tube setup chart can be used (with slight modification) with the 561, as explained later.

(more…)

If you appreciate vintage tube test gear, you will enjoy this 1940 vintage Jackson 634 Tube Tester. It is an excellent choice for anyone looking for a quality, well-built, tester that can test the VERY OLD tubes, such as #50, 01A, 1V, #10, 2A3, #15, #19, HY113, HY115, HY125, #26, #45, 71-A, #83, etc. [SOLD]

This article is also relevant to Jackson 637 tester, which is same as model 634 tester with additional integrated multimeter functionality (volts and ohms testing).

(Jackson 634 testing Cunningham CX-350 Globe #50 Triode tube)

What is really “cool” about this tester is its very small size. Measuring only 8.5 x 8.5 x 6 inches and weighing 9 lbs, this unit packs a big punch in a small size!

This tester has been in my personal collection since 1990, and it is the oldest tester in my collection (except for a Supreme 550 Radio Tester from 1936, which also has some basic tube testing capability).

Jackson 634 - 637 modernization bulletin. Click to enlarge.

This tester is so old that it did NOT come with a 9-pin-miniature socket installed — that was too modern!

(Article UPDATE, Nov 3, 2008): I found an original Jackson modernization bulletin, and the Jackson 634 and 637 testers were released in 1939. All 1939 models were sold without the 9-pin-miniature socket installed. The 1940 models were already modernized at the factory.

I have installed a new 9-pin-miniature socket, and will teach you how to “modernize” your 1939 vintage Jackson 634 also. (Jackson sockets are wired unique, and do not correspond to the 1-to-1, 2-to-2, wiring that many testers employ).

Service information and many additional photos are as follows…

(more…)

This article will discuss my method of professionally installing a socket saver into the socket panel of a Hickok 6000 / 6000A / 6005 tube tester, and is designed so that (1) you cannot even see that a socket saver is installed, (2) the case lid will close normally, and (3) the socket saver is easily replaceable when it wears out.

The Hickok 6000-series of tube testers use a plug-in socket panel instead of individual sockets affixed to the chassis. The socket panel protrudes upward, and there is no extra room between the socket panel and the case lid. Therefore, traditional installation of a socket saver (plugging it into an existing socket) is unacceptable for these testers because the case lid will not close.

Fortunately, if you are willing put forth effort, you can have your cake and eat it too! This project will demonstrate a 9-pin miniature socket saver installation, but the process can be adapted for other sockets.

When you are finished, here is what you will accomplish:

Photo above shows Hickok 6000 after my method of professionally installing the socket saver. It is impossible to see that a socket saver is even installed!

(more…)

This article discusses the B&K 707 Dyna-Jet Dynamic Mutual Conductance tube tester, including repair and calibration. Much of this discussion is also relevant to the B&K 700 (the 700 is almost identical) and the B&K 650.

The B&K 707 tube tester dates from the late 1960s into the 1970s. My manual is stamped August 1969, and a modern tube data setup chart dates 1978.

First of all, a brief explanation of the circuitry of this tester is necessary. Is this a Mutual Conductance tube tester? Well, yes and no.

(more…)