Most tube testers were not designed to evaluate balanced plate sections when testing a filament-type rectifier tube.

©2010, Bob Putnak, TubeSound.

When testing rectifiers such as 5U4, 5Y3, 5Z3 …have you ever wondered why one plate section tests stronger on your tube tester? Are all of your rectifier tubes really unbalanced?

I was recently sent an email asking for help to understand this topic.  The answer is that most tube testers were not designed to offset the difference in potential between each plate section.  For purposes of this discussion, assume that you are testing a rectifier tube with balanced plate sections.

BACKGROUND:

1.  This discussion is only relevant to filament-type rectifier tubes. While most people use the words “filament” and “heater” interchangeably, they are not identical.

A filament is a directly-heated cathode; the filament is the cathode and emits the electrons. A heater is an indirectly heated cathode; it heats a separate cathode element.  Common examples of filament-type rectifier tubes would be 5W4, 5Y3, 5U4, 5R4, 80, 83, etc.  Examples of heater-type rectifiers would be 5AR4, 6CA4, 6X4, 6X5, etc.  Therefore, a 5AR4 would not be relevant to this discussion.  Most tube testers can evaluate balanced plate sections in a heater-type rectifier tube.

2.  The purpose of the article is to explain to end-users the problems they will encounter when trying to analyze a filament-type rectifier tube for balanced plate sections using their tube tester.

Why would anyone want to do that? Historically, old-school technicians did not put much thought into needing a “balanced” rectifier tube.  Similarly, I am not aware of any vintage tube tester manufacturer that instructed the user to test a rectifier tube for balanced sections and to reject those that were unbalanced.  Nonetheless, some modern tube buyers have been told that they need to buy rectifier tubes with “balanced plate sections”.

DISCUSSION:

Most vintage tube testers were not designed to test for balanced plate sections.  It was simply not considered important. As a result, most tube testers will test one plate section stronger than the other, leading the modern user to a false conclusion that the tube is unbalanced.  In all cases that I am familiar with, the plate at the higher-numbered pin will always test higher, due to conventional filament wiring.

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This article discusses repair and calibration of the Hickok 6000 tube tester. Models 6000A and 6005 are the same with only minor feature differences that are not relevant to tube test calibration, therefore the discussion is applicable to those models as well. Serious electrical voltages are present, repairs should only be attempted by a qualified technician. Copyrighted by Bob Putnak, all rights reserved.

Introduction

Hickok 6000

Hickok 6000A

Hickok 6000 series is a compact mutual conductance tube tester. Most Hickok tube testers fall in two categories: those that use a 5 vac signal voltage and those that use a 2.5 vac signal voltage. Otherwise, most Hickok’s are remarkably alike (except for the really expensive models such as 539C or 752…). The 6000 series in the the 2.5 vac signal voltage group. The compact size of the 6000 is a welcome asset to any technician’s workbench because space is always at a premium. The 6000 series also has a replaceable socket panel.  One panel has an older compliment of sockets (4-pin through 9-pin-miniature sockets); the other panel has a newer socket compliment (compactron & novar sockets instead of the antique sockets).  This system allowed easy replacement of worn out sockets — the customer simply purchased a new panel from Hickok.

The setup chart configuration for the Shunt control gives “Good-Bad” readings, which were previously called the “English” readings in older Hickok testers.  In fact, the Shunt control was named “English” on older models.  The chart also provides a micromhos score for tubes that have transconductance (ie – not rectifiers, not diodes, not thyratrons…), and the Shunt control must be repositioned to the red dot on the Shunt control that is appropriate for that micromhos reading.  For example, if the chart says “2000″ and you had some reason to benefit from knowing the micromhos score (which is seldom the situation), you would ignore the chart’s shunt number and instead set the shunt control to the red dot near “73″ which is the 3000 micromhos range.  For most testing needs of a technician, the good/bad scale is convenient and appropriate.

Vintage is approx 1957. The 6000 sold for $182 in 1958. Dimensions: 17 x 12 x 8 (inches) and weight 16-lbs. Model 6005 is the same tube tester but integrates multimeter functions. Model 6000A has basic transistor testing capability, which I doubt that anyone uses today. Most (not all) of the 6000A that I have seen have the newer socket panel with compactron and novar sockets. Which socket panel that is best for you will depend mostly on what types of tubes you test.

As a sidenote, this socket panel makes it very difficult to install socket-savers if you still want to close the case lid.  It can be done, but it requires a lot of work and creative thinking.  See my article HERE.

Repair and Calibration

A thorough explanation of the Hickok test method, calibration voltages, and the equipment that was used to make those voltage measurements is in a United States military document TM 11-6625-274-35 for military TV-7 series of tube testers.  This information is applicable to most Hickok tube testers (not all), with the caveat that some models use 2.5 vac signal voltage instead of 5.0 vac.  It explains the voltages for the plate, screen, grid, signal and the method used to obtain those measurements. A factory calibration document for the 6000 series also exists (and has one typo mistake) and closely follows the voltages in the military TM document.

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Today was my annual warehouse spring cleaning day, so it was a good opportunity to take a “family photo” of my tube tester collection.    My collection changes all the time, sometimes daily.    I did include all of the models that I use everyday for tube sales and bench servicing, and also models that I “rotate in” regularly to keep familiar with them.  Many of these are a permanent part of my collection, others will be repaired/calibrated and sold to customers who want a quality tester that works great.

TubeSound tester collection as of April 2010

Columns are numbered left to right and models listed from top to bottom:

• Column 1: B&K 707. Jackson 648 early tweed case version, Precision 620, Simpson 555, EMC 206, Sencore Continental MU140, Jackson 648R, Simpson 330, B&K 700
• Column 2: Hickok 532, Precise 111 Mutual Conductance, Knight 600B, Hickok 800, Sencore TC28 Hybrider, B&K 550, B&K 747, Hickok 800, Simpson 1000, Hickok 533
• Column 3: US military I-177-B, US military I-177, Hickok 6000A, Precision 10-40, Knight 600C, Triplett 3423, Jackson 648S, B&K 707, Jackson 648A, B&K 707
• Column 4: US military I-177-B, US military I-177-B, US military TV-7D/U, B&K 700, B&K 700, B&K 500, B&K 700, Precision 640, Heathkit TC1, US military I-177-B, Jackson 637
• Column 5: Mercury 1000, Eico 625, Heathkit IT-21, Sylvania 620, B&K 550, B&K 700, B&K 700, Jackson 648-S, mint Western Electric KS-15560-L2, Heathkit IT-17, Supreme 550
• Column 6: Eico 666, Precision 612, Eico 667, Precision 10-12, Eico 666, Precision 10-12, Jackson 598, Philco 9100
• Column 7: B&K 747B, Sencore TC28 Hybrider, Sylvania 220, Accurate Instruments 151, Jackson 648, Jackson 648-S, Hickok 533A
• Column 8: Hickok 6000A, US military TV-10D/U, US military TV-7A/U, Hickok 6000, B&K 707, NRI Professional 70, Jackson 561, NOS NIB Sencore Continental II MU150
• Column 9: B&K 707, Hickok 533, Hickok 533, Hickok 539A, Hickok 752


One nice thing about having a large personal collection is that it makes easier troubleshooting of strange wiring problems in a customer’s tester that they have sent for repair. Being able to quickly examine another unit is often much faster than tracing the circuit. It is also nice to have another unit to compare, especially if I suspect that a component may have been replaced many years ago with a non-factory part.

How to Use a Tube Tester… and Tube Issues (in General)

by Bob Putnak, ©2010.  All rights reserved.

Your tube tester is often the first test instrument that you reach for when diagnosing problems in tube gear.  All tube testers are a compromise in functionality, compromise in accuracy, and none are perfect.  No models test for all tube characteristics.  Not even the tube manufacturers themselves had test equipment that could detect all bad tubes, or verify all good tubes, or test for all tube characteristics.  A 100% accurate tube tester is not even possible because a tube can work excellent in one circuit and not work at all in another circuit.

Tube testers were designed as a tool for repairmen to detect “bad” tubes …tubes that could be causing a problem in the item that the technician was repairing.  Tube testers do a very good job in this role.  However, many people do not use a tube tester properly, do not interpret the results correctly, or have unreasonable expectations of them.  Other people have developed poor workflow habits that need improved.  While each tube tester has different capabilities and therefore different operating instructions, here are my thoughts regarding tubes, testing, and all tube testers in general.

Table of Contents (summary of what is discussed below):

• Use a calibrated or professionally serviced tube tester.
• Do not test tubes with dirty or rusty pins.
• Tubes with multiple sections, each section must be individually tested.
• Configure test settings before inserting the tube.
• Adjust “Line control” both before AND after inserting tube.
• Filament test is always the first test made.
• Shorts Test(s) will be the second test made and must always be performed before any Emission or Gm test.
• Leakage test will be the third test made (if Leakage test is separate from Shorts test in your tube tester).
• The Shorts and Leakage test(s) are the most important tests you will make.
• For any tube, there is no one “TEST SCORE” that is “right”.
• Some tube types do NOT even have a “test score”.
• No tube tester will tell you whether an oscillator tube will work properly in-circuit.
• Now that you have some understanding how LIMITED the usefulness of a “test score” is, you can proceed to make your Emission/Gm test.
• Do NOT perform the Emission or Gm test until the tube has had sufficient time to warm up.
• Do NOT perform the Emission or Gm test for ANY LONGER TIME than necessary to get a reading.
• Interpreting Good/Weak emission and Gm test results.
• Repeat Shorts and Leakage tests again
• Know YOUR tube tester
• Noise / Microphonic tube issues

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This article discusses repair and calibration of the B&K 600 / 606  tube testers.  Both models can share the same tube setup data book, and therefore both models are functionally equivalent.    Model 606 will be example shown in this article.  Electrical voltages are present, repairs should only be attempted by a qualified technician. Copyrighted 2010 TubeSound, all rights reserved.

Cosmetically, these models look like a little brother to their larger siblings — B&K 700 and B&K 707. Model 600 shares the same color scheme with Model 700, and model 606 shares the same color scheme as model 707. The wood case construction is similar also.

Electrically, models 600 and 606 are very similar (though not identical) to the “Switch” section (bottom panel) of the 700 / 707, employing the same grid leakage test and very similar tests for Emission Quality and Shorts.

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This article discusses repair and my calibration procedure of the Precision model 10-12  tube tester.   Serious electrical voltages are present, repairs should only be attempted by a qualified technician. Copyrighted by Bob Putnak, all rights reserved.

Introduction

6 Paco 10-series tube testers from my collection

The Precision Apparatus Company (commonly known as PACO) manufactured some very high quality test equipment.  Among their offerings are the “10-series” of tube testers, such as model 10-12, 10-15, 10-40, 10-54.  The tube test method is the same in all, and the test data is interchangeable.

I have been collecting since 1990, and in my experience model 10-12 was the most popular unit.  I have found many 10-12 over the past 19 years, and serviced many more.    I have only found one different model for my own collection, a model 10-40 that you see in the photo.

Precision Apparatus 10-12 tube tester

It is easy to see why model 10-12 was most popular.  Four adjectives come to mind: Attractive, durable, consistent, quality.  Attractive — it has a beautiful furniture-grade hardwood case.  Durable — the entire unit is built-like-a-tank.  Consistent — I have always found these units to produce repeatable test results, year-after-year.  Quality — consistent test results from the “Electronamic” test method add up to a quality piece of test equipment.



Paco A-15 socket adapter

Paco G-140 Socket Adapter

The 10-series is also popular today because it will test a very large variety of tubes.  Model 10-12 has built-in sockets for antique tubes 4-pin, 5-pin, 6-pin, 7-pin large, and acorn.  It also has sockets for octal, loctal, 7-pin miniature, and 9-pin miniature.  Socket adapters (models A-15 and G-140) were later available, which adds the ability to test 10-pin miniature, nuvistor (5 & 7 pin), novar, and compactron tubes.  Therefore, if you have the socket adapter panel, you can effectively cover the entire range of tubes from antique 4-pin through modern 12-pin compactron.

The tester also has a NOISE JACK for connecting a set of headphones to audibly evaluate “tube noise.”

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This article discusses repair and calibration of the Signal Corp I-177  tube tester.   Serious electrical voltages are present, repairs should only be attempted by a qualified technician. Copyrighted by Bob Putnak, all rights reserved.

Introduction

Signal Corp I-177 tube tester

Model I-177 is a very old US Military dynamic mutual conductance tube tester that was used during World War II years.  The War Department Technical Manual is dated August 1944, and the tester calibrated in this article is dated April 1945. The unit is extremely well-built.  Due to its age and high signal voltage, the tester is only suited to test the “antique tubes” and military tubes of its era, and does not even have a 9-pin miniature socket. Although a socket adapter panel does exist to accommodate testing “newer” tubes, the tester is not suited for that task and can easily damage small signal tubes.  That said, the I-177 does an excellent job of testing the tubes of its era.


Repair

The fundamentals for starting the I-177 project: all knobs and the meter itself are indexed at zero, check all resistors and potentiometers for accuracy and replace where necessary , replace the 0.1 mfd capacitor, clean all sockets/switches/leaf-switches/pots/rheostat with Deoxit to the extent possible. I would specifically note that the I-177 has 7 carbon resistors.  Expect that most (if not all) of these carbon resistors will have increased in resistance and will need replaced.  The remaining resistors are either wirewound or precision types, and while they should be tested, it is unlikely that any would be defective.  Inspect all wiring (AC power cord, and also each wire connection at every tube socket pin).  Remove both bulbs (#81 fuse bulb and neon shorts lamp), clean bulb connections and sockets, reinstall.  The #81 fuse bulb must be only a #81 bulb (no substitutes).

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BK 607 tube tester

B&K 607 case

This article discusses the solid-state B&K 607 / 667  tube testers.  Both models use the same tube setup data book, and therefore both models are functionally equivalent.    Model 607 will be example shown in this article.  Electrical voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

This series was B&K’s clone of the Sencore Mighty Mite TC162.  While the circuits are not 100% identical, they are close enough to be considered functionally identical.  The B&K 607 weighs slightly less than 6-lbs (without setup book or manual), and size dimensions are: 34 cm L x 24.5 cm W x 11 cm D.  The case folds open and easily accommodates a full size 8.5 x 11 inch setup chart and service manual as shown in the photo above.

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This article will discuss Mercury tube testers. The Mercury Electronics Corporation of Mineola NY produced a number of tube testers in the 1960s.  All models are small, portable, and lightweight.  Popular models include 990, 1000, 1100, 1100A, 1100C, 1101.  Models and comments will be added as I find time.   Electrical voltages are present; repairs should only be attempted by a qualified technician.

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I am frequently asked by B&K and Hickok owners to explain how to replace a #83 tube with a solid state version. This question is popular because #83 tubes are scare and expensive. Other benefits are increased reliability (no tube to wear down), less heat generated inside the tester case, and less load on the power transformer. So, if you want to Do-It-Yourself, I will explain how these replacements are made.

I will preface this tutorial with a few caveats: First, this procedure is easier to implement with B&K testers than Hickok testers. Hickok factored in the load that the real #83 tube has on the power transformer, and sometimes you cannot properly set the line without circuit modification. Keep this in mind if you plan to try it with your Hickok — you may be getting in over your head. Hence, substitution may be more effort than it is worth, especially when some Hickok buyers do not want the modification and would have to undo the circuit mods that were made. This leads to the second caveat: not everyone feels that the solid-state substitution works ‘excellent’ in Hickok’s. In fact, some “purists” will not even use a Hickok with a solid-state #83 replacement. They cite the fact that silicon diodes have less voltage drop than a tube rectifier, and feel that the tube test results will not be “pure.”

Personally, I always use a solid-state replacement for B&K testers. For Hickok, I prefer to use a real #83 tube only because circuit modifications are sometimes necessary, which makes going back to a real #83 difficult for the tube tester owner or future buyer. That said, I have no disapproval with using a solid-state #83 in a Hickok, and have found that any tube “test score” differences are trivial. In my opinion, the people who argue about small test score variations are really over-thinking the purpose of testing a tube — the end-result is NOT a test score, but to ascertain whether the tube will work satisfactory in your circuit. Common sense and practicality are important.

Here it goes…

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