Heathkit Virtual Museum

TT-1 Mutual Conductance Tube Tester

TT-1 Mutual Conductance Tube Tester


  • Checks over 1100 tube types with data supplied
  • Indicates Gm to 24,000 micro-mhos
  • Constant current heater supplies
  • Ultra-sensitive grid current test
  • Direct-reading ohmmeter leakage test
  • Built-in switch-operated calibration circuit

No finer TUBE TESTER in kit form … and professional by any standard of comparison

Nowhere will you find a tube tester of this quality at so low a price! The Heathkit model TT-1 Mutual Conductance Tube Tester with its impressive list of electronic and mechanical features represents one of the finest values in the test instrument field today!

This handsomely-styled instrument with its neat, functional panel layout provides for maximum operating convenience. Versatile switching facilities accommodate present tube types and allow adding future tube types as they become available to protect against obsolescence. The TT-1 will provide quick and accurate checks of transconductance and grid current in multi-element tubes and will also check diodes, rectifiers, voltage regulators, low-power thyratrons and electron eye-tubes.

In transconductance test, mutual conductance values are read on the illuminated meter scale from 0 to 3,000 micro-mhos. Multipliers are used to accommodate Gm values above 3,000. The extremely sensitive circuit used in grid current testing will indicate as little as ¼ micro-ampere and will often indicate a "reject" after the transconductance circuit has labeled it "O.K." This test is of particular value to servicemen as grid current is often the cause of malfunctioning TV circuits. The grid current circuit of the TT-1 tests for all three common causes of grid current: gas, leakage from grid to other elements, and grid contamination (grid emission).

Diode and rectifier tubes are tested on the basis of total cathode emission. In testing voltage regulator tubes, an independent, built-in variable DC power supply is used and direct reading voltage indications are given on the meter.

Other outstanding features to be found in the TT-1 include: a Constant Current Heater Supply which protects the tester from obsolescence by supplying the correct voltage for any tube types drawing 300 ma, 450 ma or 600 ma; a Life Test, which reduces the heater voltage of the tube under test by 10%, thus giving an estimate of its future life; a "Hybrid test," which not only provides a special low voltage plate supply for testing hybrid auto radio tubes, but also features an additional DC supply for the space charge grid permitting mutual conductance tests of space charge tubes in the usual manner; a direct reading Leakage Testing Circuit; and a built-in switch-operated Calibration Circuit, eliminating the need for any standardized tubes, voltmeters or extraneous instruments of any kind. A Disconnect Switch removes all voltage potentials from possible damage during switching. "Cathode buss," "Plate buss," and "Grid buss" switches allow the operator to test both sections of a twin triode individually with only one group of selector switch settings. Individual Selector Switches allow testing any tube, regardless of base pin arrangements. Other "service designed" features are: an illuminated roll chart with thumb-wheel drive at each side, removable line cord, 110 V AC outlet, and blank socket on panel for future tube types.

The beautifully written construction manual supported by detailed pictorial diagrams, seven color-coded wiring harnesses and transformer terminal board have reduced the highly complex circuitry of the TT-1 to an easy to build level. Average construction time by technicians is 40 hours. Unit is housed in an attractive black leatherette case with white trim, nylon feet and removable top.

SPECIFICATIONS—Power requirements—Voltage: 105-125, 60 cycle AC. Watts: 10-60 (dependent upon tube under test). Plate supply: (Silicon rectifiers). DC volts: 26, 90, 135, 225 plus variable 80 to 200 (Separate DC supply for space charge grids). AC volts: 20, 45, 177. Bias supply: (Silicon Rectifier). Low range: 0 to negative 5 volts DC. High range: 0 to negative 20 volts DC. Signal voltages: 2, 1, .5, .25 volts AC 5000 cycles. Filament supply voltages: .65, 1.1, 1.5, 2, 2.5, 3.3, 5, 6.3, 7.5, 10, 13, 20, 27.5, 35, 47, 70 and 115. Currents: 300, 450, 600 ma. (Note: Filament voltage is reduced 10% during the test). Testing circuits Gm: (Mutual conductance-amplifiers) 0-24,000 micro-mhos. Emission: Rectifiers and diodes. Leakage: Direct reading ohmmeter. Grid current: ¼ microampere sensitivity. Voltage regulators: Firing voltage and regulation tolerance. Low power thyratrons: Grid characteristics, conduction capabilities. Eye tubes: Control grid characteristics. Meter AC: 1000 ohms/volt (1 volt full scale). DC: 80 ma full scale. Scales: Gm: 0-3000 micromhos. VR test volts: 0-200 volts. Leakage: 0-10 megohms. Diodes O.K. Rectifiers O.K. Line check arrow at midscale. Tube complement: (1) 3A4 oscillator, (1) 12AV6 meter control. Calibration circuit: Built-in switch operated. Socket accommodations: 4-pin, 5-pin, 6-pin, 7-pin, combination and pilot light, 7-pin miniature, 7-pin sub-miniature, 8-pin sub-miniature, octal, loctal, 9-pin miniature, blank. Line voltage adjustment: Continuously variable. Roll chart mechanism: Constant tension, free rolling, thumb wheel operated, illuminated. Dimensions: Cabinet (outside): 17¾" W x 13½" H x 7½" D. Panel and chassis: 17" W x 12¾" H x 5½" D. Shipping Weight: 27 lbs.

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