Since 1993 Copyright Notice

Hickok Tube testers

Last Update:

About Hickok testers.

You must be interested in a Hickok tube tester :) These are indeed excellent devices. Made by and for people who know what they want. There are many models made, some meeting a TV service man's requirements for speed and simplicity, some for the military which can be operated by anyone quickly, some are intended for a budget lab, even with a multi meter build im (yes!), some for the "better" labs, and some card programmable testers. You name it, Hickok had it. If you have not chosen a model yet, be aware for what specific purpose a testers was intended for. These are however not suited for an amateur who wants to become a tube doctor. If you are planning this career for yourself, get yourself digital tester. But, before you go to the advanced, "self learning" way, do not try to skip basics. So you want to learn how to fly a 40 seats, double jet engine airplane? Then you need to learn how to fly a one propeller little airplane first. For the same reason it it is recommended to learn basic behavior of tubes, first with a good old vintage tester. This will give you the required feeling for why sometimes tubes work fine in equipment, where you did not expect it, and vice versa as well. Specially this matter is only addressed by good vintage products. You will learn to appreciate the judgement of a good Hickok. Though most of them do give a transconductance number as "result" , this number is of little use by itself, for two reasons. First, because it is tested under totally none data sheet conditions. So it can only be compared to the roll chart (expected result), and if you do that, you get an amazingly reliable answer to the main question you have: Is the tube good, or bad. Second, because even if you would know the transconductance under correct data sheet conditions, you know still nothing, because no data sheet tells you what is a good or a bad number. So getting a reliable good-bad answer from a tube tester, it's what they were made for. The pure military TV7 version does not even give transconductance. The soldier in question doesn't care at all about this. Why should he? He only wants to know of the tube is good or not.

So on this light you have to see the Hickoks. They are definitely no "simple" machines however. The work very intelligent at the inside, hardly any technical issues, and the smaller ones or larger ones, are adapted to the user's needs. Most of all, they give you a reliable test result.

Repair of a Hickok. This is NOT EASY. Because inside is only cable salad, and extremely difficult working switches. You will hardly be able to follow a wire, the circuit has no "ground" as you would be used to. Rather everything inter acts with something else, and service documentation is hard to find. But, when everything works, they work fine, and need no maintenance. That is why I say, if this is your first Hickok, leave your fingers off one which is not said to be good condition.

General features

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 deck plate is not grounded. This has advantages and disadvantages. Better would be if it was not made of metal. Show plate current. Test at standard conditions for a specific tube Test dual tubes with just the flip of one switch.

Micromho and English Test

Somebody invented the unit 'Mho' as a reverse value of 'Ohm'. As if that was something useful and needed. That by itself makes me feel funny about it. In Europe they didn't want the word Mho, but for applications where it was needed,. they called it "Siemens". But in fact nobody needed it.

The ridiculous thing is now that we can call a resistor of 10 Ohms also 0.1Mho or 0.1 Siemens. The idea was, to describe the "conductivity". (conductivity is the opposite of resistance) But actually all passive components have only resistance in my healthy opinion. Now, tubes are of course active components. The output current is regulated by the input voltage. So these try to conduct. Their behavior is best written down as milliampere per Volt. Because that is what they are doing. So you change the grid voltage 1Volt, and the output current changes 5mA, and we say the tube has 5mA per Volt. (5 mA/V). That is something I can understand. But when I read a tube can do 5000 micromho, I think huh? Really? What is that? .

Anyway, this explains why USA testers have micromho on it, and many USA datasheets too, whereas European testers always use mA/V. To make it a bit more confusing, generally but not always, the Micromhos are called transconductance and abbreviated as 'Gm' and the mA/V are called 'S' for Siemens. So far for the heritage they left us.

English test

This is another of those things. English test is used by the Hickok testers, and it is a not so good way trying to say you are testing the tube under (an unspecified) load condition. The AVO company in the UK probably made the best recognized series of testers, that tested the tube under load, However, they specify exactly what load, and you could read that on the meter, and make all settings yourself.. So you could compare that with tube curves and datasheets. Apart from that, they invented this red-green scale, where the good/bad result is derived from the transconductance (datasheet !) values. So very clever, and very straight forward. In the USA that was called 'English' testing. This AVO method was patented, which was a major strike. So Hickok had to patent something else. They patented the 'English' test method, which is the RED-GREEN scale you see on most of their testers. I investigated the test results of know to be good and know to be bad tubes, and my conclusion is, it just derives a good/bad value from the already know Gm value. Same principle as AVO, but they (have to) do it in another way, in a very strange way, and in the end the RESULT is the same as with AVO. Test results: With a socket adapter, I just measured the plate current of the tube, while turning the 'ENGLISH' dial, and guess what.... Nothing changes! Only the needle moves when you turn the English dial. So I can only conclude, this changes the sensitivity of the red-green meter, and nothing else. Still the English test is the most used, since it tells you 'good or bad', and the setting of the English pot meter from the roll chart, is the knowledge of the old tube exerts, put into the tester. Admitted is, the results are very reliable, that's why I keep my Hickoks, no matter what. Some testers like TV7 have only the English test, same as with AVO. Test results: With a socket adapter, I just measured the plate current of the tube, while turning the 'ENGLISH' dial, and guess what.... Nothing changes! Only the needle moves when you turn the English dial. So I can only conclude, this changes the sensitivity of the red-green meter, and nothing else. Still the English test is the most used, since it tells you 'good or bad', and the setting of the English pot meter from the roll chart, is the knowledge of the old tube exerts, stored for ever, inside the tester. Admitted is, the results are very reliable, that's why I probably keep my Hickoks for a while longer. Some testers like TV7 have only the English test.

Hickok 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 one, so before you buy it make sure it's not rusty inside. It is a nice tester though when you have a good one, though the general rule applies here, if the case looks rotten, the inside is also. The mains voltage meter you see with this one, is retrofitted. The standard way to adjust the mains is via the main meter.

CONCLUSION: Better buy an I-177 TWO STARS *****

Hickok I-177

This was my first tube tester. I have two of those. I bought the first one in 1988 for 45 guilders (20 Euro) in the same old electronics shop, where I bought my stuff when I was a kid. He had them piled up. (Radio Kwakkelstein in Vlaardingen). Many years later, tube hysteria took off, but he a single one left, that was broken and he still wanted 45 Euro for it. I took it for spare parts, but never needed any. The thing was made to last for ever, and work without maintenance in the humid and warm countries where the US army was saving the world from communism. So even if you find a stinky old one, it might be good still. It tests all tubes from before the Noval tubes. For later tubes there is an adapter kit, which by itself is a valuable item, since it is a universal socket adapter for any tube tester, not just I-177 and not just Hickok. The I-177 is a really fantastic tester, because it gives remarkably reliable results on the good/bad scale. What is also great, it has only two knobs to choose tubes. Instead of nine (!) with the later models. They all need a calibration badly, if never done before. If this tester says the tube is 'just ok' you can bet it that is just what it is. Most of all you get used to the reading when you test the same kind of tubes, and if you see a tube which is into as good as the other, you better throw that tube away. ( or sell it on Ebay (ahem....) Basically this is THE Hickok tester for the pre-noval tubes. The later model was the TV7 , which could do also test Noval tubes. The I-177 has an interesting way it operates, and this is worth a few lines here. They use their famous patented Hickok circuit, but in the I-177 they added a potentiometer which does noting else then change the meter sensitivity. The signal going to the meter has to pass an attenuator potentiometer. This is the 'L' potentiometer. The result of that is, you can test any tube at all, and have a correct reading on the good/bad scale when you know the setting of that attenuator potentiometer. (Of course they knew that at Hickok, and this is the 'L' value in the handbook). Since the good/bad readings are done by measuring true, dynamic Gm, there is also this particular position of that potentiometer where the Gm (micro mho) scale is valid. This position is marked with 'gm' on the L Pot scale. So the good/bad reading and micro mho reading is done with the same circuit. Their patented Gm measuring circuit is the best of it's kind as far as I know. Due to this patent all other manufacturers had to work without it. It tests all known rectifiers. Also the big triodes like 300B can be tested, and as we know there are not many tube testers that can handle this tube. Not even all later model Hickoks can do a 300B. By experimenting with the settings I can now measure many unlisted tubes with it, like C3g and EM34. It's really a very nice tester, very much recommended. The circuit diagram is inside the tester on a plastic plate. (Fungus proof....), and an Excel list with all test data I found in the internet. These will all work in 100 years from now. They used to be cheap, and regardless useless. Some start to understand how good they are, and prices of those went up a lot over the last years. The bargain days are over, a good tube tester is expensive no matter what. I think these are still a good buy for the money. Here is how to find out settings for an large size tube, like KT88 or so. Find a tube with similar pin out. (that always exists) Set the L pot to the middle position and Gm Sensitivity to 15.000 Set the Bias (R) pot for highest reading. Now rotate R clockwise, until you read 90% of maximum, and this is the bias setting. May be take a little less when the fuse lamps indicates a lot of current, and you think this is too much. The calibration comes in the next step. Find the right Gm Sensitivity knob setting, so that the meter is nicely in the green. (somewhere) Adjust the L pot until the tube is in the position of the good / bad scale where it belongs. So that is just in the green for a fairly used, 'just ok' tube. Now L + R + Sensitivity is a set of information that you must use in that combination. This is a relatively high bias, which is hardest for the tube. I verified some Hickok settings, this is how they seem to do it. And that's it. Here is the KT88 setting I found that way.

A=8 B=5 Fil=6.3 L=70 R=42, Socket E, Gm switch at 6000. I have not yet tried this for small tubes, like ECC83, but there was no need also. The manual was complete so far.

t

Tester settings for all tubes

CONCLUSION: The best of this tester is the good/bad test. It discovers any potentially weak tube. Good buy when you use pre-war tubes. It can give the real Gm value of the tubes, and good/bad indication. It has no sockets for modern tubes. Use the MX949 adapter kit, and you can test any modern tube also. Make sure when you buy the adapter kit, you have the extended manual with it, otherwise you only have the adapter kit, but not the settings for it. They are all extremely out of calibration, so that needs to be done for 100% sure, unless the seller did it already for you. (I am sorry, we do not offer calibration service). THREE STARS *****

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

The A-Version uses only a 2.5V test signal, which is too high for small signal tubes, and some of those cannot be tested accurately 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, if you also want to test the later kind of tubes. Picture series about 533B here

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

The 534 is a 533 with a build-in multi meter. It is the part you see on the top left. Only for nostalgia freaks, it's too old fashioned multi meter, it has no switches, so you need to plug in cables in the right banana jacks. But it works.

For all other information, refer to the 533, also for the issue with the test signal voltage. (So 534B is much preferred over 543A ) . More information here

Four STARS ****

Hickok TV7 (technician model, small case)

This one came after the I-177, reminds me a bit of the 600. It has very few sockets. No 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 only want to do a good/bad test without knowing what or why, this is your tester.

CONCLUSION: Disadvantage: Overpriced, and little functionality. Advantage: Compact reliable, easy to access internal circuit . I regard it a shortcoming, it gives no tube parameter of any kind. Three STARS ***

Hickok 600 and 600A (technician model, small case)

Hickock 600. This is a simplified version of the 5xx series. They left away some test options like lifetime test. It has lower precision than the larger laboratory testers, 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.

FOUR STARS ****

Hickock 600A. I do not know what the extra feature of the 600A is compared to the 600. The tester you see here, is my own but I sold it in 2011. The advantage of these smaller ones is their weight and size. The only practical disadvantage I see, is some smaller accuracy, but you have to know for yourself what accuracy is a 'must' and what is a 'want'. Given the age and condition, a good 600A can measure within 10...15% which is more than you need for practical use. Picture1 - Picture2 -Picture3 - Picture4 - Picture5 - Picture6 How to use it, with pictures. This is from my own 600A: 1) Set knobs by roll chart, insert tube
2) Press Line test, adjust
3) Read tube test result. Here for 12AT7 EHX new tube. This is a strong one.

Hickok 605A. This is the same as the 600, only the 605A has a multi meter inside

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

The largest laboratory 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 imprecise The 539 series are easier to calibrate than the 750 series, but a well calibrated 750 is also something very nice.

Hickok 539A

Just purchased it from Mr. E. Dekker from Belgium. Will be described in detail later. This is how he offered it on Ebay: 'This tube tester is fully operational, all controls and roll chart work smoothly. The outside black Tolex covering does have nicks and tears but this can easily be recovered. All three meters are fully functional with smooth movement'

Actually this is the kind of description I can only advise you to look for. No uncles, no friends who tested it. The seller was the user himself, and he even pictured his tubes tested with this one. So I thought I was safe. Then when I received it I could not believe my eyes. The Tolex was fully torn away by a monkey. Here is what I received. Pic1 - Pic2 - Pic3 Next thing: 'This tube tester is fully operational' Mr. E. Dekker from Belgium writes. Well, the Gm value reads twice the vale as it should be. So it is useless. He tells me this 'must have happened in the mail'. Interestingly, he points out already in the auction text to accept no loss of accuracy that happens in the mail. Now look at that... So he already 'expected' the tester to damage in the mail. (You see what I mean?). Now look at the Ebay picture. This tells it all, but I must admit I didn't notice while bidding. Here you see a tube tested, and the meter is all in the right corner. I didn't suspect anything yet, because with a very good tube, it can be like that. Only the problem is, it does so with ANY tube I try, even a broken one. Press the test button and the meter gives a minimum of 100% reading or more, no matter what tube, even without a tube. Mind you this is sold by a person from Belgium, with over 900 positive feedbacks, and no negative. Well, this tester was broken as can be. I offered to give it back, and he writes: 'No discussion possible'. Don't understand me wrong, this is no way to complain about a bad deal here in EBAY. I put this here on the web site so you can all see what appears to be normal at the moment. Please learn from this, even people with all positive feedback do this. So this is going to be my next restoration project. Then I will show here in detail if there were any other hidden defects in this tester, and what I had to do to repair it. For the readers of this web page, this was my learning experience, and it happened to me, though I really tried to prevent it.

Conclusion: This tester gives completely useless readings, the case was wrecked up by a monkey, and the main meter sticks.

Hickok 750

Both 750 I bought, had good basic substance as I got it. No serious damage, and only worked by good technicians. Well almost. One had a sticky roll chart, which must have driven the owner crazy, ending up using a big screw driver, violently pushing the wheel, until it all broke down. But that was all of the mistreatment it got, and I could fix that at almost no cost. I had an NOS roll chart, and digged up a new thumb wheel. It seems to me, the later roll charts are simply too big, and these roll not smooth for that reason. For making it an accurate tool for daily use, there was a lot to do still. The other 750 I have appears virtually unused, but that doesn't keep the electronics from aging. The 750 is a refurbished 532, and Hickok tried to replace the 539C by it. My opinion is, the 750 is one of the best Hickoks there is, and more useful than the over hyped 539C. More about this later. What is really nice with the 750, is has additional to the classical two tube Gm test, an adjustable DC voltage of 200V, 100mA. I found both my 750's cannot supply full current and full voltage simultaneously, so that must be how they are. When exchanging the 83 rectifier for an 83V, maximum currents exceeds even 100mA, while the micromho readings don't get affected. Perhaps I will change this later, but I think this is going to take some exchange of other components too. At least I need to check this better, and for the moment I will leave it as is. The voltage option lets you test stabilizer tubes, but you can do also other things with it, as you like. If you don't know how to do that, it's better only to test things as indicated on the roll chart. Later on, I will show you how to repeat Funke W19 tests with it. The 750 differs from the smaller testes like 533 and 534 because it works with different AC test signals, instead of a fixed signal. It has this in common with the 539C. This allows testing of tubes with very high gain, so no overdrive will occur. This makes a 30.000 micromho scale possible. They put back in the load test in the 750, which the 539C is missing. I think it was a mistake, to remove that with the 539C. The latter can only measure transconductance, no load test is done. Also you can't compare the transconductance you measure with the 539C with your tube book, because the plate voltage of the 539C is too low, and simply wrong for most tubes. Next is, the roll chart data of the 539C is lower than for a new tube. That was done to give you a way to pick out the bad tubes, because in the end that's what people want. So Hickok put a non-standard roll chart in the 539C, with lower values than normal. So they printed the reject value on the 539C roll chart, not the 'new tube' value. (of course you 539C users, you all know that... he he). This makes I don't like the 539 so much. To to stop the confusion, Hickok put back in the load test in the 750, and also give standard tube data on the 750 roll chart, same as with older (normal) testers. That was a good decision. I never found any documentation about how this load (English) test is really done. The word 'English' suggest the AVO method, like in the Mk1/ Mk2...4, and CT160. I will check that later, with an oscilloscope. The oldest tester I have, using the AVO so called 'patented' method, is... a German military tester that I estimate from 1938. For the moment let's trust Hickoks experience, giving us the correct 'English' dial setting for each tube. Somebody in Cleveland Ohio (where this tester was made..) must have had a huge cabinet full of good and bad tubes, and just tried out the right settings. The roll chart is the software of the tester, so to say.

( I know it was done like this from the book of Harvey 'Gizmo' Rosenberg, who described the work of Julius Futterman. Before the war, Julius used to work for a company building tube testers, and tube manufacturers would send him all kind of tubes, to update the roll charts)

Now go to the restoration page of this tester. There were many things to do.... Please note the repairs are for both my 750's. So you may notice small differences in the pictures.

WHAT CAN BE DONE WITH THE 750 AND WHAT IS NOT IN THE MANUAL:

1) FUNKE W19 simulation. Here is something really new. With the 750 it is possible to do the Funke W19 tests with your Hickok 750. All you need is the famous Funke Blue book, which costs you about 30..50 Euro, and a copy of the card set which is on Ebay for 15 Euro. The Funke W19 is extremely popular in Europe, a top model, but it is completely ignored in the English speaking territories, except Asia who love the W19 also. Now don't ask me why that is, but this is where we are. The W19 is mainly an Emission tester, and the best and (only) one that deserves the name. Test results are undisputable. This tester proves what a good Emission Tester can look like. It is at the level of the better Hickoks, in terms or reliability, accuracy and correct test results. So if you have a Hickok 750 (or 539), read here is how to do Funke W19 tests on it!

2) Forward voltage of rectifier tubes. This is of particular use in the laboratory If you don't know much about tubes, and only want a quick result, you should use the classical test a by the roll chart.

Example: The 80 rectifier to my experience should have a forward voltage of 25..40 Volts at 60mA to be good. Where 25V rarely happens, and above 45 the 'bad' range begins. Also note what it does at lower filament voltage. A good rectifier does not significantly change it's forward voltage if you do so. On the other hand, if the forward voltage is higher than normal, and you set the filament voltage one click higher, and the tube significantly improves by this, the tube is worn out. You can try to get those results in-line with the classical test as on the roll chart. To do this test, just set up the tube from the roll chart first. Then set the 'Adjustable Voltage' to zero, and the test know to position 'H' for high. Flip the Vr-Mils switch to mils, and slowly increase the voltage until you see the milliamps go up. Check the forward voltage, this is when Vf begins. Then go on until you have 60mA and read the Vf now. Then do the other plate (switch setting is at the roll chart). You will see this is very easy to do, and you learn a lot about the tubes. 3) Forward voltage of Power Zener diodes. Same procedure as with tubes. Only you have to prepare an adapter this. Remove the base from an old octal tube, and connect two wires to plate and cathode. Take the connections for the VR105 tube. Make sure you don't reverse the Zener, and don't boost 100mA into a short circuited Zener, that is probably not so good for the tester. You will be surprised how bad solid state zeners actually are, they have high temperature drift, and bad load regulation compared to tubes like VR150 or VR105. 4) Continuity tester. This one is from the manual actually, but it's nice one. You can use the 750 as a continuity tester, when you set the 'shorts' switch for position 4. Then put two probes in the 'grid' and 'plate' connections. Because the tester has an isolated chassis, this is of no danger. Then the neon lamp will burn, below 200K resistance. Nice for checking switches, connectors, etc.

CONCLUSION: FIVE STARS ****

Hickok . TV2. Military (laboratory model)

It can test all tubes under real conditions. It comes in the same category as German Neuberger RPG375 tester, though the last is card tester, not switch operated. TV2 is unpopular though, but I never had one here, so I cannot say what is the reason. What is unattractive (for me) about a TV2 is following: It is a tube analyzer, not a tube tester. Now when you have an analyzer, you often want to connect a multi meter to it somewhere, like measure the filament current with a digital meter, or one of the voltages. It often comes down to that when I use the RPG375. So a voltage test point AND a removable current bridge on all tube connections. Particularly THIS is why I use an analyzer like U61B or RPG375. Next thing is, you can set the plate voltage and grid voltage nicely by the data book, and then get a test result called 'Percent Quality'. Whatever that is supposed to be, that is not what to know. When I must set exactly plate voltage, and grid voltage, I am sorry, but then I want to see the plate voltage and Gm as a result, and additional some 'Quality' indication in percent. Still for that I rather have the red-green scale if the 750A or 600A. Then I know what I have. So personally, I think this is what makes TV2 a strange thing. It seems to me people don't know what it's worth, I have seen them go on Ebay in nice condition for 200$. Also see people ask 1800$ for it, which is definitely not what they are worth. When you are prepared to that much, you better buy a guaranteed to be mint condition Neuberger RPG375 or Metrix U61B, and enjoy that tester for the rest of your life. Working on Hickoks means they are easy to access inside, but the wire spaghetti makes you very tired. Actual failures are small, but hard to find. While working on a Neuberger RPG375 is a pleasure. All inside parts are nicely arranged in a row, on metal sub chassis, with clear cabling. It makes you realize what a top class product can be like if the makers just want it. You can repair a Neuberger RPG375 with an uncalibrated multi meter, and basic electronics knowledge. You can't say that from a Hickok. (However, this does not apply for the older Neubergers, these are very hard to service as well. However, the compare here is between the TV2 and the RPG375.

Hickok . MX-1258/U Tube Socket Adapter

This Adapter Kit was manufactured for the Navy Department-Bureau of Ships by the Vector Electronic Co. of Los Angeles, California. It consists of nine types of adapters, mounted within an aluminum transit case approximately 6" x 9" x 2 1/2" complete with handle. The adapters are secured within the case by means of mounting clips. An addition clip for securing the instruction book is provided in the case lid. Pin straighteners for the 7 and 9 pin miniature bases are permanently mounted in the center of the transit case. The tube socket adapter kit is intended for use in general electronics testing on equipment employing electron tubes. The nine adapters contained in the kit provide the facility for testing circuit conditions with practically all of the commonly used electron tubes.

 

Hickok known issues, problems and general information Hickok company photo archive