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 Post subject: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 3:31 am 
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I picked up a 539C for next to nothing and would like to be prepared when I place it into service.

Can anyone recommend any preferred operating tubes for it?


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 4:56 pm 
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Howdy. Welcome to the forums.

Not sure exactly what you are asking. Like all Hickok testers, it uses an 83 and a 5Y3. Brand? I don't think it really makes much difference.

John


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 6:00 pm 
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Yes, that's what I mean, those two tubes.

The manual lists them as 83, 5Y3GT/G. Is the 5Y3GT/G same as 5Y3GT? I see quite a few 5Y3GT on Ebay but not many 5Y3GT/G. It appears they are the same though.

There's a wide range of prices. Any preferred brand?

I guess I should open it up and see what's inside...


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 6:09 pm 
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Yes they are the same. The extra /G in the part number is only to allay any fears regarding use of the GT version to replace the G version.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 6:29 pm 
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The 83 in those will last forever. I highly doubt anyone ever had to replace a worn out one, but rather only had to replace one that failed for other reasons.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 6:40 pm 
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When you get the 83 be sure the carbon coating on the plates is not flaking, the flakes can short the tube and may damage the instrument. Reject any carbon flaky 83... Ignore any mercury globules, that is normal from shipping.

Let the tube tester burn the two tubes, especially the 83 for half an hour before taking readings. No need to burn for half an hour after that, though some warm up time may be helpful. The burn is to vaporize most of the mercury, then when it cools the mercury will condense into the lowest safe spots.

Chas

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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 7:52 pm 
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Two questions:

1. On removing the panel, I see a lot of screws on it. Do I remove just the outer ones or some of the inner ones as well? I can't seem to find info on disassembling this thing.

2. This unit is a later one with the plastic, square meter. Although the manual states 115v operation, there's a Youtube video that insists on using a step down transformer to avoid damage:

https://www.youtube.com/watch?v=lX3lLs95AuU


Should I do this?


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 8:07 pm 
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There's the screws around the rim and one in the back or bottom of the case to hold the transformer bracket. I run mine on a neutralized 117v constant voltage transformer; I don't have to worry about what the line voltage is doing. Although there are harmonics generated that could theoretically cause an uncertainty in the Gm measuring circuit, I have found no problem with this device (except for that darn buzzing sound)


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 10:44 pm 
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Chas wrote:
then when it cools the mercury will condense into the lowest safe spots.

And then the tube gets turned sideways inside the tester.... :wink:


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 11:09 pm 
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Thanks for the very useful info so far. So, I opened it up. Looks very original on the inside, including Hickok labelled tubes. Case has the original warranty sticker, suggesting it's from June 1968.

1. The 83 is flaking.

2. There is a black standoff (?) that rattled around the bottom . Could have been there before I unscrewed the cover, can't recall.

3. There is also a nut that was loose. Can't match it to anything yet.

4. There is a white powder on some of the metal. Putting it to my nose, it smells rather awful. Hard to explain, as I'm unfamiliar with it.

Any thoughts appreciated.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 11:14 pm 
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The white powder is likely copper oxide. From the brass screws.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 11:17 pm 
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Scott wrote:
Chas wrote:
then when it cools the mercury will condense into the lowest safe spots.
And then the tube gets turned sideways inside the tester.... :wink:
Of course it does, common mode of operation is vertical. The initial 20 minute burn will re-acclimate the distributed mercury for both initial manufacture and transportation, to living in a horizontal environment. winkedy, wink, wink...

The white powder is cadmium flowers, the result of the cadmium plating reacting in a moisture condensing environment. It can be removed with a water dampened cloth, wearing gloves, dispose of the cloth. Do not further "sniff" the dust, cadmium is toxic in that form...

The dust may return, it can be sealed using white shellac on a shellac moistened cloth, only a thin film is required.

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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Wed 15, 2021 11:21 pm 
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Dust thou art and to dust thou shalt return.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Thu 16, 2021 3:14 am 
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Regarding cadmium: in a post on this same site:

https://www.antiqueradios.com/forums/vi ... 5&start=20

Findm-Keepm says:

"If cadmium is present as a plating, and Cadmium Chloride(a white powder, the byproduct of heat and non-alkaline moisture) is present, merely wipe off any loose corrosion products and dust with a damp cloth, using either isopropyl alcohol or deionized water to dampen the cloth ... Seal the cloth in a polyethylene bag and treat the cloth as Hazmat, and furthermore, do not let it come into contact with any strong alkali or alkaline solutions (like bleach, sodium hydroxide or potassium hydroxide.)."


...and this should be done outside and wearing a mask and gloves.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Fri 17, 2021 1:42 pm 
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Location: Long Island NY
Regarding the tubes, every Hickok tester I have ever seen with original tubes had RCAs for both the 83 and 5Y3. I'd simply stick with RCA if replacements are needed. I would not worry too much about that 83 tube. Lots of them look like that. You'll notice that the mica spacer is right over the tops of the plates so there is little chance anything can get inside. Just give it plenty of time to warm up and redistribute the mercury vapor, as previously suggested. There is no plate voltage on it unless one of the Gm buttons is pressed so warming it up will not endanger anything.

As for the blossoming cadmium, you should be careful but there is no reason to call out the men in moon suits to deal with it. The fact that it has blossomed means that it has already reacted and formed compounds with the environment so it is not as bad as "fresh" cadmium that might become airborne as dust if you drilled, ground, or sanded a new piece of plated metal. Just brush and wipe up the dust as suggested. This is a good place to use one of those N-95 masks and rubber gloves you have been saving for a special occasion. If you don't use the gloves then wash your hands thoroughly before eating; ingesting the stuff is not good for you either.

Have you tried to power the instrument up yet? There are no electrolytics in the power supply so you do not have to go overboard with dim bulb testers, variacs, or stuff like that. Set it up to test a tube you happen to have on hand and see what happens. You will undoubtedly want to clean the switches and controls, and replace the few capacitors that are in there, but it is important to get an idea of what condition the tester is in first. If all goes well it will work as it is supposed to. But people have reported bad meters and power transformers, and some of the specialized potentiometers can fail, and those are real show-stoppers. You want to verify that you are at least starting with a basically good tester before you dig into it. Otherwise if it doesn't work when you are finished you are going to be scratching your head trying to figure out if something you did caused the problem or if it was there from the beginning.

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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Fri 17, 2021 5:27 pm 
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I had the same thing with my 539c and the 83. Those flakes can cause shorting and I have seen it when testing them. Get a new 83. That black piece and nut most likely came froma socket saver that was removed. Just study the manual, final adjustments are made holding down P4.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Fri 17, 2021 5:49 pm 
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I have not powered it on.

I'll replace the 83 and clean it up before I do anything else.

I'm not sure I'm going to keep it. I have two stereo tube amps and a B&K 747 works just fine for these needs. The 539C was just too good a deal to pass up.


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 Post subject: Re: Recommended tubes for Hickok 539C
PostPosted: Sep Fri 17, 2021 9:26 pm 
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The 747 is a good tester and easier to use.


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