Precision Model 10-12 "Electronamic" Tube Master
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The model 10-12 came out in 1947 and can test a large array of receiving tubes. This tester picks up where my other testers fall short, and not only can it test 4, 5, 6 and 7-pin tubes of the 1920's and '30's, but also Octals and Loctals, and 7 and 9-pin minatures, and the latest tubes that came out right up to the 1970's. It tests Compactrons, 10-pin Decals and Minatures, Magnovals, Novars and Nuvistors using the Coletronics adapter. And testing charts for new tubes were still being published into the 70's. Not many tube testers are this versatile.
Precision called the model 10-12 Tube Master an "Electronamic" tester, incorporating Precision's "Electronamic Master" tube testing circuit that indicates the performance merit of a tube in a single direct meter reading on an English reading "Replace/Good" scale. Precision also said the Master Element Lever Selector system, and Master Control Socket, for tubes not yet designed, provides the ultimate in testing flexibility and positive insurance against obsolescense. And they were right: it can test just about any receiving tube and Tube Masters are still valued tube testers 74 years later.
This set was missing it's documentation when it found me, but I downloaded a copy of the manual, plus a schematic and some supplemental tube charts for free online. There's also remastered copies available at a price, for a little better quality, and already printed and bound.
The workmanship is excellent and all the wiring is neatly routed and laced. The tester contains only one tube, a 5Y3 rectifier.

I replaced half-a-dozen out of tolerance resistors on the "E" switch, plus three paper capacitors, the neon "Short" lamp and all the rock hard rubber feet on the bottom and back side.
To separate the tester panel from the case the red and black grid cap wires, that exit through holes in the storage compartment of the case, need to be unsoldered. Likewise, the power cord needs to be unsoldered if you want to get the case and panel more than a power cord's length from each other.
The case looks like maple. The veneers are starting to seperate so I needed to do some regluing and then refinish the outside of the cabinet. Inside it still looks good.
The Coletronics B-16 socket adapter adds seven more sockets to Tube Master. There is a supplement published by them that has the settings for all the newer tubes that can be tested with this adapter.

There are also a couple of other adapters made for the 10-12, but I don't have those.
Page created 3/30/2021
Last edited 4/4/2021