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.
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.
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.
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.”