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.

The exact tester that you see in the photos below is available for sale at $350 plus shipping.

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…)

For Sale: very rare W-41187 Auto Expressionator tube. $95 + postage. This is an extremely rare tube that goes into the output stage a few 1930s Crosley round-dial console radios and in theory works as a “sound expander” to colorize the sound. Good continuity, tight base, polished pins. Try to find another one! This is the only one I have ever owned in 18+ years in the radio collecting hobby.

W-41187 Auto Expressionator Tube

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.

For Sale: $600 for this LOT of 6 Telefunken 12AX7 ECC83 17mm Long Smooth Plates Tubes, Made in Germany. Used, but Top Quality. All test excellent, very close to new. Characteristics of all six tubes: Made in Germany, Diamond bases, Long 17mm perfectly smooth plates, Top round getter, the first five tubes have “4 ribs on top of glass envelope”; the sixth tube (diamond base code 12,2) has a smooth top glass envelope, there is no silkscreening left on any of the tubes, new white boxes will be supplied for professionalism, and each box will be labeled and test scores recorded.

Test results (diamond base code is provided in parenthesis):

• Tube #1 (11,2): Triode #1 = 102, Triode #2 = 105
• Tube #2 (14,2): Triode #1 = 98, Triode #2 = 98
• Tube #3 (4,2): Triode #1 = 98, Triode #2 = 101
• Tube #4 (11,2): Triode #1 = 93, Triode #2 = 94
• Tube #5 (02,2): Triode #1 = 104, Triode #2 = 98
• Tube #6 (12,2): Triode #1 = 93, Triode #2 = 100
• No shorts or leakage
• Test scores from my professionally calibrated Jackson 648A dynamic plate conductance tube tester. (Scores of 70+ are good, 100 range is new). Since tube testers vary in design and methodology, your test results may vary.
• As you see, some these test new, and all test excellent.
• 

For Sale: Sylvania #50 engraved-base Audio Triode tube, TESTS NEW. Truly a beautiful tube, Made in USA, Sylvania engraved-base, ST-glass, Black Plate, clear-top, large solid square getter. Nice and clean, shiny flashing, shiny pins, no visible plate wear. Awesome.

Tested perfect new test score, scoring 1550 micromhos on the true micromhos scale with calibrated Hickok 6000 tube tester (a score of 1500+ is perfect new), and also without shorts or leakage. For those of you without a true micromhos scale, it tests very strong into the “Green-Good” range. Truly a top-quality audio triode. $280.

For Sale - Sylvania 50 triode tube

This article discusses repair and calibration of the EICO 950A Resistance-Capacitance-Comparator Bridge, commonly used as a capacitor tester. Also discussed are the PACO C-20, EICO 950, and EICO 950B tester. The exact EICO 950A unit pictured in the photos below is for sale at $149 plus shipping, rebuilt and calibrated as described below. The PACO C-20 unit is for sale at $139 plus shipping. 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.

When the bridge is unbalanced, the magic eye will remain closed.

PACO C-20 tester

Eico offered three models, the 950, 950A, and 950B. They are very similar, and most of this article will be relevant to all three models. Likewise, I have updated this article to include coverage of the PACO C-20 unit, which is almost identical to the EICO 950B.

These models use a balanced bridge that measures capacitance from 10mmf to 5000mf (some models 2000mf) and resistance from 0.5 ohms to 500 Megohms (some models up to 200 Megohms). 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. This is a very high quality test instrument when properly rebuilt.

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Early this year I found this vintage Colin B. Kennedy Corp radio. Model 62LS lowboy console with model 54A shortwave unit. I recently finished rebuilding this radio. It is available for purchase (local pickup preferred, but crating and shipping can be arranged but will be quite expensive). It would make a beautiful addition to any old home or turn-of-the-century mansion. This beautiful antique radio is more than a radio — it is a beautiful piece of furniture as well. Colin B. Kennedy Corp marketed themselves as the “The Royalty of Radio”, and the high quality craftsmanship is readily apparent.

Colin B. Kennedy Corp model 62LS lowboy console radio with model 54A shortwave unit.

This is actually the second Kennedy console radio in my collection.

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For Sale: $2,400. Shopped out and works fabulous.

Kenwood KT-917 Pulse Count Detector FM tuner

Some people believe that the Kenwood KT-917 is the finest FM tuner that was ever manufactured. This is truly the cream of the crop. Pulse Count Detector, high build quality, Made in Japan.

A fellow in my community decided to trade-in this KT-917 for some quality tube audio gear. He had his eye on some nice tube gear in my collection, and his KT-917 needed repaired for quite a long time. Since he was currently more enthused with rediscovering his music tastes (vinyl and CD), he decided to forego repair and trade for tube gear.

Repairing the KT-917 was straightforward. The tuner was not decoding, and some quick troubleshooting revealed a defective MC1496 IC, which is a Balanced Modulator-Demodulator designed for FM detection.

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Here is a rare tube — a Marathon MX-280 Globe #80 rectifier tube featuring MESH PLATES construction!  Not only that, but each section tests very strong Emission, comparable to an NOS #80!

In 18 years of collecting, I do not remember ever seeing another Mesh Plates #80 tube.  Look at that Glow!  You can see right through the Mesh Plates into the filament!  This would be a beautiful tube for any serious collector.  You could really impress your friends with this one.

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