Daniel Schoo

Calibration Testing of the Hickok Model 600A Tube Tester

Version 2.1, May 1997

Daniel Schoo

SETUP

1.
Turn on the tester and allow it to warm up for 5 minutes.
2.
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.
3.
Push switch P7 and rotate the LINE ADJUST until the meter pointer rests exactly over the LINE TEST mark in the center of the meter scale. Release P7.

DC VOLTAGE TESTS
Using pin 8 on the octal socket as common, measure the following voltages using a 1000 ohms per volt meter. A high impedance digital meter may be used if shunt load resistors are connected across the input to the meter. For steps 1 and 2 use 240K. For step 3 use 51K. For step 4 use 10K. All resistors are 5% 1/2 watt. If any voltages are incorrect see the TROUBLESHOOTING section at the end of this document for assistance.

1.
Push switch P4 and measure pin 3 on the octal socket, the plate circuit supply. The reading should be 150 volts plus or minus 5 volts.
2.
Push switch P4 and measure pin 4, the screen circuit supply. The reading should be 130 volts plus or minus 5 volts. Hold P4 and push P1. The screen voltage should drop to 56 volts plus or minus 3 volts.
3.
Set the bias control clockwise. Measure pin 5, the control grid circuit supply. The reading should be -39 volts plus or minus 1 volt.
4.
Set the bias control to 22. Measure pin 5, the control grid circuit supply. The reading should be -3 volts plus or minus .2 volt.

AC VOLTAGE TESTS
Using pin 8 on the octal socket as common, measure the following voltages using a high impedance AC voltmeter.

1.
Push switch P1 and measure pin 3 on the octal socket, the plate circuit supply. The reading should be 19 volts AC, plus or minus 1 volt.
2.
Release switch P1 and push P3. The reading should be 36.5 volts AC plus or minus 1.5 volts.
3.
Release switch P3 and push P5. The reading should be 170 volts AC plus or minus 5 volts.
4.
Release switch P5 and push P2. The reading should be 292.5 volts AC plus or minus 7.5 volts.

SHORT TEST CALIBRATION
R28 sets the shorts test voltage. To adjust R28, connect a 220K resistor between pins 8 and 5 on the octal socket. Set the SHORTS switch to position 2. If necessary adjust R28 until the short lamp just begins to glow. After the test return the SHORTS switch to the TUBE TEST position.

MUTUAL CONDUCTANCE READING TEST
Verify that the panel switches are set up to the conditions as given in SETUP step 2 at the beginning of this section, (JR 5347-2) FILAMENT at 6.3 volts. Set the BIAS control to zero and the ENGLISH control to the dot near number 73. Connect an AC voltmeter to pins 8 and 5 and measure the grid signal voltage. The AC grid signal voltage should be 2.5 volts plus or minus .05 volts.


Figure 1

For the following mutual conductance test you will need to set up an isolated current limited source of AC voltage. Use the setup drawing in figure 1 to connect the equipment to the tester. Be careful because improper connection can cause serious damage. Connect the source to pins 8 and 3 of the octal socket. If the main meter deflects downward instead of up when you perform the test, swap the connections to pins 8 and 3. All voltages are measured directly across the secondary of the isolation transformer.

Push P4 and slowly adjust the voltage source up to exactly 50 volts. Observe the reading on the tester meter. The correct reading is 2000 micromhos on the 3000 scale. After taking the reading set the voltage back to zero and release P4.

TROUBLESHOOTING
Always test the two rectifier tubes first if trouble is suspected. The plate supply voltage is used as a reference when setting the AC line voltage adjustment. If the plate supply is not correct, check the resistors in the AC voltage metering circuit R24 and R25. Also check the meter movement and verify that it indicates full scale when exactly 500 microamps are passed through it. The metal plate mounted on the side of the meter is a factory applied magnetic shunt. By loosening the mounting screw and sliding the plate back and forth, small adjustments can be made to the full scale deflection of the meter.

The control and screen grid voltages are effected by adjustment of R6. If adjustments are necessary to the control grid bias voltage measured in step 3 of the DC VOLTAGE tests, adjust the slider that is electrically connected to the end terminal on R6 until the voltage is correct. To set the screen voltage with both P4 and P1 pushed, adjust the other tap on R6 for a correct reading.

NOTES
The component designation numbers given refer to the parts listed in the Hickok schematic diagram included with the operators manual for the model 600A. The calibration voltages and procedures listed here also apply to other models of Hickok tube testers. Other testers in the 600 series like the 605 and other model series like the 800 may be checked using the same procedures but the component designations given will be different from those given here for the model 600. Hickok is a registered trademark of the Hickok Electrical Instrument Company, Cleveland Ohio.