How to Calibrate Hickok Tube Testers

How to Calibrate Hickok Tube Testers;

The method of calibrating Hickok tube testers may vary largely depending upon what sort of equipment you possess.
If you are going to calibrate a TV-7D/U, most resistors are trimmer potentiometers, so the problem just in front of
you is to turn them to make your tube tester indicate the true value of the vacuum tube under test.
However, if you are to calibrate TV-7/U, or older type models, most shunt resistors are not trimmer resistors but
fixed value resistors, therefore the work concerned is a rather complicated problem; you need to devote a lot of time
and energy in measuring the status quo of the tube tester and in putting the tube tester into the status quo ante, the former status.

In Japan there is a proverb that goes like this; A skillful craftman does not need any particular tool; that is correct all
right, but if you are going to do some kind of work you need a certain tools, a least TS-352 circuit tester, a digital multimeter, a decade resistor box, and hundreds of 1/2 w or 1w resistors to make use of in trying to make up the resistor
value to complete your calibration usually by trial and error method.

It took me about ten years until I learned this method; but I believe everybody must be doing the same way. I began in a very primitive way by searching for proper value resistors required inside my junk parts boxes, but in time I learned to
do the same thing in a more systematic way, that is, to make use of a couple of variable resistors fastened to a plastic board in order to find out a proper value neccessary.

Tools Absolutely Necessary for Calibration; Good Tools Help You Work in a Short Time.

#TS-352 analog circuit tester which can read 0.5 volt with its meter scale, internal
property 1 kilo ohm per 1 volt. Various articles on the web say that you can produce same
situations by simply connecting 250K ohm resitor across tester's probes. However, it is
easier to purchase one good-working TS-352 tester at Ebay auction, and use one for your purpose.

#Decade Resistor Box can be used to decide a proper resistor value particularly needed to
rectify the wrong value of old tube testers' shunt resistors.
If the reading of the meter is too high, you connect a resistor across the resistor already used; whereas if the reading of the meter is too low you can connect a new resistor in series with the existent resistor, thus making more current flowing into the meter.
If you don't understand the basic priciples concerning this technique you can learn by reading about the shunt resistor's work for the meter, but I believe those who attempt calibrating tube testers already know and understand what I
describe all right.

# You have got to possess hundreds of resistors for making up proper value resistors for your purpose. Their prices
may be 25 cents each, but if you buy in quantities, say 100 pieces
for one kind, prices may come down to almost ten or five cents each. I bought lots of them,
and now I possess over several thousands of them in my inventory. And I believe I have invested over 800 US dollars
for purchasing them all.

With your TS-352 analog tester you can check up the plate voltage, screen voltage, and
bias voltage of the tube under test exactly as required for conducting your authentic calibration. If you do this with your digital multimeter, meter readings will turn out to be higher than the true value of the voltage. This applies particularly to plate and screen voltages; bias voltages and filament voltages can be read correctly by digital multimeter all right. And in case of TV-2 tube testers all can be measured by digital multi-meters all right.

As regards the resistor value changes after the lapse of forty to fifty years's time, there is an interesting report by elementary school kids' experiment during their science class.
A science teacher over there gave his pupils some homework to be submitted to him; that is
to check up the values of old resistors left in the junk boxes of grand-pa's. And the result is interesting enough; most resistors measured showed higher values than the original values;
in some rare cases lower than the original ones.

(To be continued)