How to test tubes not listed on Hickok I-177?

Gentlemen,

To thank the Author because you find the post helpful or well done.

Dear Marco,

it is not so easy to use I-177, and its MX-949 adapter, to test tubes not listed in their data tables. I-177 circuit is very simple and does not allow the setting of the operating parameters as specified in the manufacturer’s data books. There is just a single anode and no screen grid voltage supply. The sole parameter you can change is the control grid negative bias. The settings given in the tables for L and R potentiometers refer to a triode connected test circuit, with fixed drive and fixed supply. There is no direct relation among the couple of values for R and L, grid bias and meter sensitivity, and the effective grid bias and Gm given in the tube data books. You have to find new settings for any tube not listed in the tables and in their updating pages, using some elsewhere calibrated references.

TV-7 is similar to I-177 and has the same limits. Even if it can measure a lot of miniature and new tubes, I never saw a setting table for old European tubes, as side-contacts or German metal ones.

The I-177 is my preferred meter to perform quick checks of U.S. tubes. It may be easily adapted for checking European tubes electrically similar to the types listed, only differing in the envelope or in the socket. For other European tubes, a European tester could be the easier solution.
 

Regards, Emilio

To thank the Author because you find the post helpful or well done.

Hello Emilio, first of all thank you for your very informative answer, I really appreciate it. I think you already guessed that I don't have money to buy nor room enough to store another tube tester, not even to mention the annoyance of going through dozens of them to find one (supposedly) properly working.

On the other hand, I'm not looking for the full accuracy or speed the I-177 can give. In most cases one only need to know if the tube is completely shot or works somehow. In other words, for example, I'm not expecting to get the handy "good / replace" reading for which Hickoks are famous: as far as I'm concerned the L potentiometer can be left on "Gm" position so that the answer may be read directly in MicroMhos. And as long as the datasheets are now easily available, one always knows how many MicroMhos the tube under test is supposed to show. By doing so, the potentiometer R seems to be (correct me if I'm wrong) the only thing which actually needs to be set up, all the rest (wiring, etc.) being given by datasheets.

So now the question sounds like: may the setting of potentiometer R be known once one has the datasheet? Or can the R potentiometer be set empirically through measurements (voltmeter or oscilloscope) performed directly on the tube socket under use?

Finally, what about deducting the setting of R by comparison with other tube testers for which the data are widely available even for european tubes? Like our SRE emission tube tester, which reports data for european and US tubes as well?

To thank the Author because you find the post helpful or well done.

Dear Marco,

may be I was not able to properly transfer my thought: absolutely no idea to blame or judge your decisions. Nor I want to annoy anyone with considerations about the many models available: everyone uses the model he gets at the best of its capabilities. I tried just to explain how difficult may be to find a new couple of R and L values for each new tube. The tube data updating was the most complex and expensive after-sale task of any tube tester manufacturer.

The values given in the data tables of the tube tester to set both R and L potentiometers cannot be directly derived from the data given in the datasheet, which are referred to the typical circuit, with certain anode, screen grid and other electrodes supply values, well defined input signal amplitude and the nominal load.

In the I-177 you can only perform a measurement in the circuit given in fig. 6 of the operating manual, the result being then related to the Gm. Any tube under test is actually connected as a triode, with fixed plate voltage and fixed input signal voltage. You can only move the grid bias voltage, potentiometer R, to stay within the proper dynamic range and the safe operating conditions for the tube. As you can easily verify from the data tables coming with the set, the settings of the grid bias potentiometer are not proportional to the negative bias values given by the manufacturers for each tube. The difference is evident when you give a look to some tubes rated for relatively low B+ voltage, as those for battery operation. Just one example: the grid bias specified in GE Essential Characteristics for both the 1G6 or the 1L4 is 0V. But the I-177 tables give R setting values of 13 and 16 respectively. These operating points were probably chosen to limit the anode current to safe values and to prevent the grid going positive.

The use of data tables of different models is possible provided that models use the same circuits and the same voltages. I do not know if Hickok made export models with data for European tubes. Neither for the I-177, nor for the newer TV-7, I have ever seen any official supplement data concerning European old tubes. The TV-7 tables give test data for some CV and some recent European tubes.
It is possible that someone has put on the Web a couple of setting values for say the EL3, but how reliable are them? Here the reasons why I still prefer the quick and reliable I-177 whenever possible, but use different sets for European tubes, a Chinaglia or an Avo depending upon the case.

Regards, Emilio

• Simplified Gm test schematic (11 KB)

To thank the Author because you find the post helpful or well done.

Emilio, thanks for your detailed insight.

I see that the only path would be to undergo a cooperative work with owners of more than one tube tester and with samples of known-working tubes to deduct setting values.

However, it seems that no one else is interested in this subject except you and I, so it is more wise for me to forget it and skip to something else.

You've been very kind, thanks a lot again.

To thank the Author because you find the post helpful or well done.

I am in need of a Hickok Model 531 (KS-13588-L1) operation manual.  Is there one online that can be downloaded?  The tester I possess seems to be in good working order.  Some of the labeling is missing on the facing as well. 

Thank You!

Keith Hardy

• Hickok 531 Tube Tester (58 KB)

To thank the Author because you find the post helpful or well done.

Dear Keith
You have a good chance to get technical papers if you use the link "Create New Model" on the search page and enter your instrument. After acceptance you can load up your picture and you can use the link for acquiring the technical information.

To thank the Author because you find the post helpful or well done.

Hello Ernst,

Thank you for your response. I am new to this handy site and still learning my way around.

Cheers,

Keith

To thank the Author because you find the post helpful or well done.

Dear Keith
You have done very well - but I had to correct small things. You can look at the process of accepting by clicking "Pending Models" under Community on the Search page. You then also see then it is up.

To thank the Author because you find the post helpful or well done.

Marco,

I have been using the I-177 for many years and was interested in this thread. Years ago I converted my tester to test newer tubes by building an adapter into the lid. This was done from plans in QST.

I have used a tube chart designed for the Hickok 6000 dated 1971. This seems to work pretty well. Of course the adapter you are using should work using this chart also. The L and R settings in this chart are on a 0 to 100 scale instead of the 0 to 80 of the 177 so a new dial or some math calculations are necessary.

I am no authority on this but wanted you and Emilio to know that I am interested and would like to be informed of any new ideas you may have.

Also, there is a link which has some information on this. Just scroll down to the Hickok I-177.

http://www.jacmusic.com/Tube-testers/index.html

Regards,

Dale
 

To thank the Author because you find the post helpful or well done.