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 Post subject: 83 mercury diode question
PostPosted: Jun Sat 01, 2019 12:13 am 
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I have read that the two diode sections in 83s need to be well balanced. How closely balance do they need to be? For instance, when checked on a Hickok 6000 an 83 might read 2250 on diode #1 and 2450 on diode #2. Would this be considered closely balanced or not? In checking several 83s I find that consistently diode #1 reads less than diode #2, by about 150 to 200.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Sat 01, 2019 1:56 am 
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Unless it's compensated for each side will read differently. It depends on which filament lead is used for reference on the tester.

Your tube is good.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Sat 01, 2019 2:28 am 
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All directly heated rectifiers (two heaters in series) measure this way, as one half of the heater has 2.5V more net voltage. Reverse the heater connections and the other half will measure higher. Some testers have different load settings for the two halves.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Sun 09, 2019 8:36 am 
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The thing about the 83 rectifiers is they aren't supposed to lie on their sides. Does your
tester mount them horizontally ?


https://frank.pocnet.net/sheets/093/8/83.pdf

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Mon 10, 2019 1:41 am 
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Well, at first I was going to say they are mounted vertically - when they are tested. But, how about the 83 inside the Hickok 6000? Guess what, it is mounted horizontally. I'm not sure just what that means. It is contrary to the tube specs.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Mon 10, 2019 1:50 am 
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Yes, they are horizontal in the testers. I have 2 mil testers. Been that way for
about 60 years.

But I don't think the 83 tubes were ever intended to last 60 years, NIB.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Mon 10, 2019 2:13 am 
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I guess my question would be: Does the horizontal mounting affect the accuracy or durability? If it's been working for 60 years it would seem not durability.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Mon 10, 2019 4:02 am 
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I was often getting inconsistent readings from my B&K 707, found the 83 was erratic on one side(yes it's mounted horiz under chassis). Testing it vertically on a Precision 912, it was still erratic(the 707 cannot test big pins, though would be possible with a 80 to 5Y3 adapter). Anyway that was probably four years ago and the used 1940s 83 I installed has been fine operating horizontally.

I have to ask, what tube tester mounts tubes horizontally when under test? I've never seen one.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Mon 10, 2019 12:20 pm 
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What norm said. AND the work just fine horizontally in the Hickok design. I am quite certain the Hickok designers knew all about this tube

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Tue 11, 2019 12:16 pm 
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The issue is that the filaments in rectifier tubes are subject to sagging if the tube is horizontal. It takes long hours at full load current for this to happen, but when a filament sags enough to touch the plate, it takes the tube out in a bright flash of glory. Since most rectifier tubes had oval or square plates, the usual recommendation was that if the tubes had to be installed horizontally, the long sides of the plates should be in the vertical plane, giving the filament maximum clearance if it did sag.

In a tube tester, there is no load on the 83 unless one of the Gm test buttons is pressed. So the load is highly intermittent and briefly applied. Nor does it often reach the maximum rated load current or PIV of the tubes. The filaments never get hot enough, for a long enough period of time, to develop much sag. Maybe if you had a tester that was used constantly and bounced around a lot, the tube filaments sagged and broke sooner than they would have if the tubes were vertical, but anecdotal evidence is that most of the tubes held up fine and gave long service in tube testers despite the mounting position.

With regards to balance, I think Alan Douglas once mentioned that the two sides of the rectifier should be balanced within five volts of each other to avoid affecting the readings. How he determined this, I do not know.

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 Post subject: Re: 83 mercury diode question
PostPosted: Jun Wed 12, 2019 2:53 am 
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Location: Powell River BC Canada
Alan Douglas said the arc voltage drop of the 83 was kept to 10 volts.* ( Since
the Hickock circuit patent 1,999, 858 measured the net current difference between
the alternate half cycles of the AC anode supply, caused by the AC grid signal supply,
biased by the 5Y3 full wave rectifier, the difference in voltage drops between a vacuum
(5Y3) and a mercury (83) was crucial.

The ration of plate to filament drops is high. +/- 2 volts makes a difference in an 83 with
10 volt arc drop. but not in a 5Y3 with a plate to filament drop of 30 volts) my opinion.


The word SAG in Alan's book refers to VOLTAGE , not filament droop.

*Tube testers and classic electronic test gear Douglas, Alan,Sonaran, Arizona ,2000,

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