During the tube era a bewildering number of companies built instruments designed for use in radio service shops.  Among them were the four whose logos appear above, as well as Allied (Knight), B&K, Burton Rogers, Clough-Brengle, Dayrad, Delta, Du Mont, GE, Heath, Jackson, Paco, Radio City, Radiotechnic, Readrite, Service Instruments, Simpson, Superior, Supreme, Sylvania, Triumph, Waterman, Webber, Weston, and others.  Some parts manufacturers also made instruments, usually geared to testing the types of parts they manufactured.  These include Aerovox, Cornell-Dublier, Mallory, Solar, Sprague, Thordarson, Tobe, and others.

The 533 was perhaps the ultimate radio shop tube tester of the late 1940s.  Although it could be used in the field it's a bit large, so Hickok introduced the 600, almost identical but without some of the 533's esoteric tests and much more compact (533 and 600 use the same roll chart).  In addition to conductance, shorts and gas tests the 533 also can test noise (microphonics), and has a filament voltage reduction life test that indicates how strong the cathode emission is.  It handles 4-, 5-, 6- and both sizes of 7-pin tubes, as well as octals, loctals, 7- and 9-pin miniatures, acorns, circular and in-line subminiatures and pilot lamps.  I've owned my 533 for about twenty years.  The 3200-44 (01-Mar-1961) roll chart for the 532-533-533DM-534-534A-534B-600 models is online at the BoatAnchor Manual Archive.  See also my small collection of Hickok Bulletins.

On rare occasions I'll find a tuned circuit that just doesn't seem to be tuned to the correct frequency.  The 90651 can determine the resonant frquency of any tuned circuit in seven bands from 1.7 to 300 MHz.  I don't own the low-frequency coils, but have made some of my own for use in the AM broadcast band.  The 1957 Radio Shack catalog listed the 90651 at $61.50.  The Type 90651 manual is online at the BoatAnchor Manual Archive.

My 844 is still in the condition in which I received it - in pieces.  When I get around to putting it back together it will look much like the Model 840 shown here.  The AC/DC voltmeter has ranges of 12, 60, 300, 600, 1200 and 6000 volts.  The ammeter ranges are 1.2, 12, 60, 300 and 1200 ma and 1.2 amps.  The ohmmeter ranges are 400 ohms, 100k, 1 meg and 10 megs.

Here's the only truly modern instrument in my shop.  I bought this for use at work a few years back but now it's in the shop at home.  A 2 GHz frequency counter is overkill there, but it allows me to calibrate RF and AF generators that I'm restoring.

This interesting item was used in radio shops to set the buttons on radios to the frequencies of local stations.  The eight tank circuits are slug tuned and selected by push-buttons which held station tabs.  The first two tanks can be set to IF frequencies as low as 405 kHz.  My 171 came complete with the original box, manual, leads and an unused book of station tabs.

Simple isolation transformers have a 1:1 turns ratio.  More expensive units have selectable taps, as in this RCA transformer which can provide the correct voltage to a chassis from a variety of line voltages.

My 1167-A is in pieces - I've been collecting parts to restore it and recently found the last one I need - a copper-oxide rectifier.  The 1167-A combines two instruments in one case - the 1166-A Free-Point Auxiliary Set Tester (left) and the 1125 Universal VOM (right).  It handles 4-pin through octal tubes.  These illustrations are from Triplett Price Sheet No. 41 where the 1167-A cost $37.50.  The 1936 Lafayette catalog listed the model 1167-A at $24.50.