Calibration Testing of the Hickok Model 600/600A Tube Testers
Version 4.0, September 2006
© Daniel Schoo
Use this procedure to test and calibrate the Hickok Model 600/600A mutual conductance (AKA transconductance)
tube testers. Except as noted, all of the readings are taken with a 1000 ohms per volt meter. If an accurate 1000 ohms per
volt meter is not available a modern high impedance analog or digital voltmeter can be used with appropriate shunt
resistors in parallel with the input to simulate proper loading. The following resistor values should be used: 10 volt scale
use 10K, 50 volt scale use 51K, 250 volt scale use 250K. All resistors are 1/2 watt 5% carbon composition.
Calibration will be easier if you supply AC power through a constant voltage regulation type transformer to do the
tests, but this is not essential. Recalibrate the tester any time either rectifier tube is replaced. The correct type #81 fuse lamp
must be installed in the tester or false readings can result. For the identification and location of adjustments and for
troubleshooting refer to the ADJUSTMENT CHART immediately following the test sequence.
It is assumed that the person performing the testing and adjustment is knowledgeable in electronic service and
aware of the dangers in working on equipment using high voltages. Do not attempt to service equipment if you are not
experienced in such work. Serious shock or death could result in improper action or procedure.
PREPARATION
Remove all of the screws around the outside of the panel that hold the tester to the case. Remove the tester from the
case and set it up on spacers so that the front panel is facing up in the normal operating position. Before applying power
adjust the mechanical zero on the meter to set the pointer exactly at the zero line on the scale.
Turn on the tester and allow it to warm up for 5 minutes. Set the tester programming switches to these settings: 6.3
JR-5347-2 0 0. Set the SHORTS switch to the TUBE TEST position. Do not insert any tubes in the test sockets.
LINE ADJUST
1. Push switch P7 and rotate the LINE ADJUST until the meter points directly to the LINE TEST mark in the center of the
meter scale. Release P7.
ENGLISH POSITION
2. Rotate the ENGLISH control fully counter clockwise and verify that the pointer lines up with the 0 mark on the scale.
BIAS POSITION
3. Rotate the BIAS control fully counter clockwise and verify that the pointer lines up with the 0 mark on the scale.
SHORTS TEST
4. Connect a 220K resistor between pins 8 and 5 on the octal socket. Set the SHORTS switch to position 2. The neon shorts
lamp should glow. Return the SHORTS switch to the tube test position.
FILAMENT VOLTAGE TEST
5. Connect an AC voltmeter to pins 2 and 7 of the octal socket. While observing the reading on the meter, rotate the
FILAMENT switch from the minimum through the maximum voltage positions and verify that the voltage agrees with the
setting. The readings should be within plus or minus 10% of nominal. Return the FILAMENT switch to the 6.3 volt
position.
PLATE VOLTAGE TEST
6. Connect the negative lead of a DC voltmeter to pin 8 of the octal socket. Connect the positive lead to pin 3. Push the P4
GM button and read the voltage. Normal plate voltage is 150 volts plus or minus 5 volts. Release P4.
SCREEN VOLTAGE TEST
7. Move the positive lead of the DC voltmeter to pin 4 of the octal socket. Push P4 and read the screen voltage. Normal is
130 volts plus or minus 5 volts. Release P4.
REDUCED SCREEN VOLTAGE TEST (Later versions only, earlier versions do not have this.)
8. Hold P4 and press P1. The reading should drop to 56 volts plus or minus 3 volts. Release P1 and P4.
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