LCD Meters Hickok 533A

Hickok Electrical Instrument Co
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Sampler1
Posts: 3
Joined: Tue Feb 05, 2019 9:10 pm

LCD Meters Hickok 533A

Post by Sampler1 »

I seen a photo of a mod done by a guy ; "Hickok 533A - Roger Kennedy Modified"
Has anyone seen any info on this mod adding a DC plate current meter,DC Bias and Line meters? Im curious as to the Meter spec's and where he tapped in.

Best regards
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Sampler1
Posts: 3
Joined: Tue Feb 05, 2019 9:10 pm

Re: LCD Meters Hickok 533A

Post by Sampler1 »

Hummmm, Kind of quiet in this forum I guess.

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Admin19
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Joined: Sun Dec 11, 2011 1:55 pm

Re: LCD Meters Hickok 533A

Post by Admin19 »

This was done by Roger Kennedy, I have been in contact with him several times, and he is most helpful. He is a true specialist with the Hickok testers, and doing things with almost scientific precision.

If you ever opened up an Hickok, you'll realize they are extremely user unfriendly, and I am saying it carefully. There is nobody who can advise you for free, like cut this wire here, and connect this wire there. Because it's unknown, and you will only find out yourself when you understand how this tester works in the first place. The functioning is weird on pupose, for the sake of the patents. Provided you can get the schematics at all, for your version of the tester. So this is where Roger steps in. He is not doing this for a give away price, but it's worth the result, if that result is what you are looking for.

The question is if you want that at all. Because this tester is testing tubes at very strange anode voltage. It's nice to see those numbers pass by digitally, but the working points are way off the data sheet values, so you can do virtually nothing with those results. This tester tests for transconductamnce. Most people do not know this, but transconductance is not a fixed number. It varies wildly by changing the working point, and in a second step, trying to relate that to such a thing as a data sheet, almost nobody is capable of. So when 6SN7 has a Gm of 2600, by the data sheet, that means at 250V, 9mA. When your Hickok tests that at 150V, 7mA or whatever strange working point, to get the 2600 again, that is their cleverness. But you will have a hard time, relating that strange working point to a data sheet. When you get it presented digitally with 0.1% precision, it's not the precion that you need. It's the CORRECT working point you need, and Hickok is not doing that at let's call it a working point, which is certainly NOT the one you were lookingn for. And you can not change the voltage, only the current.

You can change the current on your Hickok (by using the "bias" potmeter) and voila: Look at the wild changes of Gm. What does that tell you a about a specific tube you are testing? Nothing. Because those changes are normal, but not a soul can qualify those results.

You will have little use for any test results, the very moment you set the bias different from the roll chart. Like this you can say almost nothing about it, at least not if Gm responds as it should. Since you can only refer to the Gm when you set the bias pot to the roll chart value. And that, the analog version can already do. And no, you can not set it to the data sheet value for any tube at all.

So this Mod is a nice play tool, when you are in love with a particular Hickok tester type. These testers do work really nice, and I like them very much myself. So when it's worth the money to you, you can do it. But do not expect ou can extract all kind of meaningfull data from the tube all of a sudden. For that you better use the Russian L3-3. That whole tester costs less than the modification, and when you can understand and work on a Hickok, you sure can sure understand the L3-3. Because it has no patents and no tricks inside, and the standard circuitry provides already all those measurements.

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