Testing panel meters

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The article will discuss a cheap and easy way to test panel meters. The meter in your tube tester is an example of a panel meter. Occasionally you see flaky meter operation and suspect that the panel meter may be defective.  Most techs know that it may not be safe to test a panel meter by placing an ohmmeter across its terminals — this attempt can ruin the panel meter (depending on the ohmmeter used) and will not reveal all of the panel meter specs anyway.

Most panel meters in vintage equipment (such as tube testers or capacitor testers) will be milliammeters or microammeters.  The good news is that these panel meters can be tested, although extreme caution must be exercised.  One mistake and you can easily ruin the meter, so “do not try this at home” until you have practiced with a large variety of junk meters and have sufficient experience and confidence in your skills. Even then, “triple check” everything before you proceed.

Simpson 2600 Calibrator

Simpson 2600 Calibrator

Many people think that you need to have expensive equipment to test panel meters.  It would be nice to own a Simpson 2600 Laboratory-grade Calibrator (which cost $1,620 in 1965 and weighs 132-lbs).  But you can make do with the following basic equipment: a variable power supply, a quality resistor decade box, a quality multimeter with mA and µA capability, and another quality digital multimeter that will accurately test millivolts.  Likewise, you need an understanding of what you are trying to accomplish.   Keep in mind that Ohm’s Law teaches that voltage, resistance, and current are all interrelated, therefore a panel meter that has its faceplate scale in “volts” CAN be tested as an ammeter.

In the following discussion, I will demonstrate testing a panel meter.  You will (1) determine the full-scale spec of the meter (using the printed scale as your reference for full scale), (2) evaluate whether the meter action is smooth and accurate across its entire range, and (3) determine the internal resistance of the meter.


Hickok 6000 socket saver installation

This article will discuss my method of professionally installing a socket saver into the socket panel of a Hickok 6000 / 6000A / 6005 tube tester, and is designed so that (1) you cannot even see that a socket saver is installed, (2) the case lid will close normally, and (3) the socket saver is easily replaceable when it wears out.

The Hickok 6000-series of tube testers use a plug-in socket panel instead of individual sockets affixed to the chassis. The socket panel protrudes upward, and there is no extra room between the socket panel and the case lid. Therefore, traditional installation of a socket saver (plugging it into an existing socket) is unacceptable for these testers because the case lid will not close.

Fortunately, if you are willing put forth effort, you can have your cake and eat it too! This project will demonstrate a 9-pin miniature socket saver installation, but the process can be adapted for other sockets.

When you are finished, here is what you will accomplish:

Hickok 6000 after professional installation of socket saver

Photo above shows Hickok 6000 after my method of professionally installing the socket saver. It is impossible to see that a socket saver is even installed!


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