(very uncomplete) overview of Hickok Tube Testers

These are the most seen series:

1. Models before the Hickok patent. Very old testers, not practical today.

2. Technician models, Large case

Gives a quick result, easy to operate. Has some special features like life-time test. Medium precision. Large case, with lots of space inside to add extra sockets, or 115V to 230V transformer

3. Technician models, Small case

Simplified versions of the large case testers. Low precision, small size, low weight.

4. Laboratory models

Require more settings, but can also do more. Have higher generic precision, due to less compromises with the circuitry. Some have even a separate filament transformer.

5. Card matic

 

General features of all Hickok testers

  • Micromho (=ma/V) readings, by means of a patented Hickok two-tube circuit which you will find in all testers with some variations. Some of the later solid state testers had the same circuit. Because of this "standard" circuit, each tester is a good one.
  • Future Tube life indication. The "English" reading with most of the testers. Some Laboratory models have additional tests.
  • Case is rugged and large, leaving us today plenty of room for upgrades
  • Wooden case is extremely rugged. Deck plate is nicely engraved and solid.
  • Gas Test. This is done with a standard test circuit, by putting a very high series resistor in the grid. The idea is, that tube gas gives grid current, and this will generate a small voltage over this resistor. The small voltage will add to the DC bias voltage, and change the bias of the tube. This change has always it's limits no matter what causes it. So regardless if it is gas if leakage, we always call it "gas" when you have a Hickok.
  • Noise test. This seem a nice method, though I must admit never tried it. You have to connect am AM radio receiver antenna to the noise test output, and if there is any noise, this will give loud crack sounds on the radio.

Not a feature of all Hickok testers:

  • Electrical safety. The non-grounded deck plate is DANGEROUS.
  • Show plate current.
  • Test at standard conditions for a specific tube
  • Test dual tubes with just the flip of one switch.

Micromho test

Micromho usage makes things more difficult as we need. The word Mho is the reverse of Ohm, just because Mho is in ma/V. To make it simple again: If a tube is 2.7mA/V it reads 2700micromho. That's all you need to know.

English test

The word English refers to the AVO company, which uses a way to derive good-bad results from the Micromho readings.

 

49-A

Will upload pictures later. This is an older kind of tester, probably already having the Hickok patent inside. s

  TV10, technician model.

531 (technician model, large case)

This is the same as the I-177, only the 531 is the civil model. It doesn't have the potted transformer, and anti fungus treating of the I-177. It is a very old model, so before you buy it make sure it's not rusty inside. It is a very nice tester though when you have a good one. The mains voltage meter you see with this one, is not a standard with all models. The standard way to adjust the mains is via the main meter.

I-177. Military (technician model, small case)

Can test most older tubes, but has no noval socket. (adapter kit exists for that) Inside parts are fungus and anti-rust treated, which pays off. They are always very good looking inside, also when stored bad. It can test English or in micromho. Quick test of both systems of rectifiers with only one switch, which is very rare with Hickoks. Also tube setting is quick, because there are only two knobs for this. Very good tester, belongs to my favourites. More information here

533A, 533B (technician model, large case)

The A-Version uses one 2.5V test signal, which is too high for small signal tubes, and some of those can not be tested acurately or not tested at all. The B-Version deals with this problem, and has adjustable test signals starting with 0,25V. Tubes that need lower input signal, are tested with lower signal. The ranges are switched automatically when you change through the Gm scales. So 533B is much preferred over 533A

More information about 533B here

534A, 534B (technician model, large case)

The 534 is a 533 with a build-in multi meter. For all other informations, refer to the 533, also for the issue with the test signal voltage. (So 534B is much preferred over 543A )

More information here

TV7 (technician model, small case)

This one came after the I-177, reminds me a bit of the 600. It has the more modern sockets. A disadvantage is, it fails the direct reading of Gm in micromho. It has very straight forward way of operating it. What is nice, is the test switch and the short-circuit switch are combined, so you go automatically through the short test, before doing functional testing. Very popular tester. Switches inside are ceramic. Very good service documentation exists still today, and it has nicely arranged calibration settings inside. So if you don't need the Gm results, only what to know the English value (meaning good/bad) this is a very nice tester.

 

600 (technician model, small case)

This is a simplifed version of the 5xx series. They left away some test options like lifetime test. The main disadvantage is the lower precision, and there is no way to calibrate it more precise than what it was made for. Reason is, the Gm reading is done with a particular setting of the English scale. For instance for the 3000mmho scale, you must set the English pot to the red dot "3000". Then read on the 3000mmho scale. So this saves the range switch, the 5xx series has. The 600 has a red dot painted on the English scale for each range. However, the 3000 dot is almost at the beginning of the scale, may be only 10...15 wire windings away from it. When you try to set it precise, you will notice each winding of the wire wound the pot meter will give a change of the meter indication. So no matter how small the dot is, at the beginning or at the end of the dot, you have two different readings. Needless to say, the position of that dot is hypercritical. It means you depend on the original factory precision, and you have no practical way to make the tester any better than that. However the small size and simply way to operate it, made it very popular. It sort if did what the not-so-critical technician needed, and frankly speaking it still does so today.

 

605A (technician model, small case)

This is the same as the 600, only the 605A has a multimeter inside

539A, 539B, 539C (laboratory model)

The largest laboratry testers. For me, these all have one BIG disadvantage: the English scale is missing. So the tester doesn't tell you if the tube is good or bad. You're supposed to be able to tell this yourself. The so called advantage of the bias setting with it's own voltmeter is only a marketing gimmick, because the scale is too tiny, and unprecise.The the 539 series are easier to calibrate than the 750 series, but a well calibrated 750 is also something very nice.

750 (laboratory model)

The 750 is a Laboratory tester, that Hickok replaced the 539 series with. 539 was a bit difficult to use, and the 750 has been given back the good old "English" test that the 539 was missing.

TV2. Military (laboratory model)

It can test all tubes under real conditions. Inspired on the German Neuberger testers. Not so popular, because they are not so easy to operate.