by Bob Putnak, ©2010.

Of all the subjects that I have discussed, I receive the most inquiries about my HP Officejet “scanner system failure” repair article.  That article also fondly mentions the old-school Laserjet’s, and I had several inquiries about repairing them.  These old dinosaurs are still useful to any small business that prints traditional business text documents or for printing schoolwork.   So here is an article about how I have repaired and refurbished these Laserjet 4L and 4P printers in the past (not so much anymore!)  Do not attempt if you are not qualified to perform such repairs or do not want to risk further damage or inability to reassemble your printer.  The basic concept is similar with other models not shown here, although disassembly will be somewhat different.

HP Laserjet 4L

These printers were built like a tank and page-feed problems are the most common complaint.  A general overhaul will take care of most of these issues.  In summary: the printer is torn down, thoroughly cleaned with compressed air (including the 4 optical sensors on the mainboard), rubber rollers are treated with rubber rejuvenator, the sticky-stuff is cleaned off of the relay coil, the relay coil arm is wrapped once with thin black electrical tape.  If you have a dead printer, you will also inspect the power supply fuses, although a blown fuse is usually the symptom of a real power supply defect.

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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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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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HP Officejet R-series

As a fan of vintage tube equipment, it should come as no surprise that I prefer older quality computer equipment.  In this article, I explain how to repair “Scanner System Failure” problems in a vintage HP Officejet R-series multifunction scanner-printer.  Model R40xi is shown in the photos, but all models (R40, R40xi, R60, R60xi, R80, R80xi) repair the same.  In fact, many similar HP multifunction units of this era are repaired in similar manner.

First, let me explain why I feel that these vintage HP units are worth repairing.  Why fix an “old parallel-port printer” when new models are so cheap?  Like most things in life, you really do get what you pay for, and if HP paid me to take their new models (with the assumption that I actually had to use them), I would not be interested.

During the Lew Platt years, HP was making top quality products.  This period of quality was from the early 1990s (Laserjet 4-series and beyond) through the Officejet R-series of 1999.   The hardware during this time was built-like-a-tank, and when compared to today, the ink supplies were reasonable (although they certainly seemed expensive at the time).

Let us look at the economics: Officejet R-series uses a #45 cartridge, holds 42-mL ink, retail cost $30.  This HP45 can be purchased for $5 on eBay. Modern HP cartridges hold as little as 5-mL ink and cost $15 — which is 4.2 times more expensive using retail price comparisons.  If you consider surplus #45 cartridge prices as your comparison, the cost to operate a new HP printer can be  42-times more expensive.  And if you are an environmentalist (or anyone who hates frivolous waste), ask yourself whether it is environmentally responsible for HP to manufacture an ink cartridge that only holds 5-mL or 10-mL? Certainly not, and those puny cartridges are only sold to pretend that the new cartridge price is cheap, when in fact it holds 4-to-8 times less ink.   That is an insult to your intelligence and an affront to the environment.

In another example, a modern HP toner cartridge (for a current model) costs $99 retail with approx 2,000 page yield.  Surplus HP toner cartridges for the old 4-series, 5-series, or 6-series can be purchased for approx $20-$30 on eBay, and have 3,000+ page yields.  Vintage Laserjets have been known to be run strong with 500,000 page cycles.  Any chance you will get even 50,000 page cycles with a modern unit? Good luck with that.  And how many Nag messages from the new drivers to “buy more ink” would you click on during that time?  Well — no nag messages with old HP units!

So when you analyze the situation, the answer is obvious why I fix these old HP units.  (1) High build quality of the hardware, (2) low cost of use (ie – cheap ink), (3) OS drivers that respect you as a person, without bloat or nag screens to harass extra ink purchases, (4) ink that does not “expire” because some Corporate Executive wanted to sell more ink to pay for his/her 7-or-8 figure CEO salary + stock options + benefits + perks + Golden Parachute retirement package.

Let us compare the “new” models.  By ‘new’ models, I consider any model released in the Carly Fiorina era and beyond to be ‘new’.  The only benefits that I can see in the new models are USB connection (which is easier for most users but otherwise adds no functionality) and much better color printing.  Since I have no problem with parallel ports and only print black-and-white, those issues are not important to me. Otherwise, it is my opinion that the quality of the new hardware is much lower than the older models, the cost of consumables (ink/toner) is outrageously expensive, the computer drivers are bloated and filled with nag messages that harass you to “buy more ink”, and some models “expire” the ink cartridges based upon a random date.   If you feel respected as a customer with that experience, more power to you.   Personally, I am not interested in participating.

With that explanation, let us move on to the repair.  As always, repairs are only suited for experienced electronic technicians with suitable training.  Also, it is useful to take a video of your repair project so that you can reexamine your work if you get stuck during reassembly.

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This article will discuss repair and calibration of the NRI Professional model 70 tube tester. High voltages are present, repairs should only be attempted by a qualified technician. Copyrighted, all rights reserved.

NRI 70 beautiful hardwood case

Introduction

The high-quality craftsmanship of the NRI Professional model 70 tube tester is readily apparent. It has a beautiful hardwood case (appears to be oak or birch) with finger-joint construction. Eight rubber feet protect your desktop in both the working position and the standup position. Internally, the tester uses a large beefy transformer and quality Pace meter movement. The tester has very small size, measuring only 10.75 x 10.75 x 6.25 inches (27cm x 27cm x 16cm) and weighs a hefty 10.4 lbs (4.7 kg). Most of the weight is due to the large transformer and hardwood case.

The NRI 70 has eight built-in sockets consisting of 4-pin, 5-pin, 6-pin, 7-pin large, 7-pin miniature, octal, loctal, and 9-pin miniature. All sockets use standard wiring (1-to-1, 2-to-2, etc.), and the control lever numbers correspond to their RTMA pin numbers (Lever 1 controls socket pin 1, Lever 2 control socket pin 2, etc.) (more…)

(©2008 Bob Putnak, all rights reserved.)  This article discusses repair and calibration information for a number of vintage capacitor testers that all use the same fundamental test circuit.   The article currently covers the EICO 950-series, PACO C-20, Knight KG-670, Heathkit C-2 and C-3, etc.  (More models will be added on an ongoing basis as I find the time. ) All of these models are almost identical in functionality and circuitry.

PRECISION REFERENCE CAPACITORS — For those of you doing your own repair, I sell a set of precision reference capacitors for $29.99 + $3.50 postage USA/CAN.  Complete set of 3 reference caps (1 of 200 pf, 1 of 0.02 µf, and 1 of 2.00 µf).  All caps guaranteed accuracy 1% or better and the 200 pf cap will be variable for maximum flexibility.

You NEED precision reference capacitors to achieve an accurate capacitor tester.  If you want a 2nd set of precision capacitors to rebuild another unit, or a set to test the accuracy of your own tester, you can buy two sets for $49.99 + $4 postage USA/CAN.

Other values of precision capacitors are available by request.  Email for details.

These units are known as a Resistance-Capacitance Bridge, an R/C tester, but are most commonly used as a capacitor tester. Extreme caution must be followed with any vintage capacitor tester because very high voltages are present during repair and while operating. They should only be used by knowledgeable technicians.

EICO 950A

PACO C-20 tester

Knight KG-670

Heathkit C-3 (dark color scheme)

Heathkit C-3 (light color scheme)

These models use a balanced bridge that measures capacitance from 10mmf up to 5000mf and resistance from 0.5 Ω up to 500-MΩ. During component value testing, the magic eye tube serves as the null-indicator. When the bridge is far from balanced, the target area of the magic eye tube glows completely closed green, and in fact overlaps. As the pointer dial approaches balance point, first the overlapping disappears and eventually the entire target area of the eye tube is completely open (dark). The bridge is balanced when the maximum dark area is indicated, and you can then read the value of your component on the faceplate scale.

Most models use the magic eye tube for both Leakage testing and component value testing.  With the Eico 950A, leakage of Paper/Mica caps is indicated by the #1629 magic eye tube, but electrolytic leakage is indicated by the Neon bulb.

Any technician who repairs vintage tube equipment (such as tube amps, antique radios, vintage jukeboxes) will find that a quality capacitor tester is a useful test instrument.

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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.

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