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 Post subject: #83 tube
PostPosted: Jun Tue 01, 2021 3:10 am 
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Location: Elmira, NY
I’m doing some maintenance and updates to my Hickok model 539C tube tester. Upon visual inspection I notice something somewhat strange about the #83 Mercury vapor rectifier tube.
It appears the black coating on the anodes is flaking off leaving white metal underneath.
I know the black globes sputtered on the glass envelope is typical and normal with these tubes, but the flaking I’ve never seen before.
I tried my best to photograph as attached.
I have no reason to suspect this tube is bad as the tube tester seemed operational, but I have no way of testing or no tube to substitute.
I believe the tube is only used as a regulator and for the 15v constant drop. I’m wondering is this tube good or should it be replaced.
Your thoughts please.


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 Post subject: Re: #83 tube
PostPosted: Jun Tue 01, 2021 12:36 pm 
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You kind of answered your own question..... it’s working so it’s a good tube

To ease your mind you could buy a spare to have on hand , but they last almost forever. Which is a sort of nebulous measure of time but.,,,

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 Post subject: Re: #83 tube
PostPosted: Jun Tue 01, 2021 3:54 pm 
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Location: Long Island NY
The black anode coatings on tubes is usually a mix of graphite and a binder. Its purpose is to help cool the anodes by improving their ability to emit infrared radiation. It does this by eliminating reflections that would tend to keep the IR inside the tube. It looks like something went wrong with the binder on that tube and the coating flaked off.

It has to be remembered that the 83 tube, like the 5Y3 and so many others, was not meant for a single purpose. They were developed and sold for a huge number of applications--not all of which needed every feature built into the tubes. In this case the 83 is only used a few seconds at a time when the P4 or P5 buttons are pressed so its anodes never get hot enough to overheat. If there's one place a failed anode coating would not matter, it's in a Hickok tube tester!

But there is one point to consider. That coating is probably at least somewhat conductive and if particles or flakes of it get inside the anodes, or between the support wires, there could be a little fireworks show inside the tube. Not harmful if it burns out right away, but if it shorts the tube it could be bad news for your power transformer. So I would keep the tube horizontal like it is when the tester is in its normal position let the flakes of material fall harmlessly to the side wall of the tube. Don't bounce it around or shake it up more than you have to.

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 Post subject: Re: #83 tube
PostPosted: Jun Tue 01, 2021 5:27 pm 
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The 83 in my 1971 B&K 707 was full of those black splatters. I suspect at least partially, was mercury that had been subject to arcing. One side would only fire intermittently, made testing erratic. Testing in Precision 912 gave same results. I'd consider your tube to be near end of it's useful life.

Installed a used one without splatters(1947 code date), been fine for last five years or so.

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 Post subject: Re: #83 tube
PostPosted: Jun Wed 02, 2021 9:31 pm 
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I wouldn't trust that tube in my tester, there is a chance of that material causing a short. It's not a regulator but supplies the power to test tubes. The meter is in a bridge circuit and there is possible damage to the meter if it shorts.


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 Post subject: Re: #83 tube
PostPosted: Jun Thu 03, 2021 12:28 am 
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Location: Elmira, NY
Thanks for the comments. I ordered a replacement. Your right, it’s too risky to have that material flying around inside the envelope. A new tube wasn’t that expensive compared to the possible damage. I’m thinking it might also cause an imbalance in emission.
The Mercury splashes didn’t concern me as much as possible interelectrode shorting.


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 Post subject: Re: #83 tube
PostPosted: Jun Thu 03, 2021 12:33 am 
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Location: Elmira, NY
Chris108 wrote:
The black anode coatings on tubes is usually a mix of graphite and a binder. Its purpose is to help cool the anodes by improving their ability to emit infrared radiation. It does this by eliminating reflections that would tend to keep the IR inside the tube. It looks like something went wrong with the binder on that tube and the coating flaked off.

It has to be remembered that the 83 tube, like the 5Y3 and so many others, was not meant for a single purpose. They were developed and sold for a huge number of applications--not all of which needed every feature built into the tubes. In this case the 83 is only used a few seconds at a time when the P4 or P5 buttons are pressed so its anodes never get hot enough to overheat. If there's one place a failed anode coating would not matter, it's in a Hickok tube tester!

But there is one point to consider. That coating is probably at least somewhat conductive and if particles or flakes of it get inside the anodes, or between the support wires, there could be a little fireworks show inside the tube. Not harmful if it burns out right away, but if it shorts the tube it could be bad news for your power transformer. So I would keep the tube horizontal like it is when
the tester is in its normal position let the flakes of material fall harmlessly to the side wall of the tube. Don't bounce it around or shake it up more than you have to.


I never seen the coating deteriorate like that, must have been a defect of manufacturing. I’m sure this tube never seen maximum service and/or overheating. And, only one anode at that.


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 Post subject: Re: #83 tube
PostPosted: Jun Sat 05, 2021 7:37 pm 
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Location: Auburn, AL
A number of folks have noted that one anode tends to do most of the work in the hickok circuit. You can see that one side of the tube glows a brighter blue than the other when you do the GM test and draw power from the tube. I don’t know what would cause the tube to ever see enough current getting drawn to cause the anode to overheat in a Hickok tester, unless there was something wrong with the tester. It might be worth investigating that everything is functioning as it should, and that there’s no cause for excessive current to be drawn in use.

Also, that 15 volt drop is inconsequential in practice in the Hickok circuit. It’s a bug, not a feature. But it’s a bug that doesn’t cause harm. If solid state diodes like the 1n4007 had existed when Hickok designed their circuit, they would have used them rather than the 83 tube. In fact they did use solid state diodes in their later designs, as did a number of other companies.

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 Post subject: Re: #83 tube
PostPosted: Jun Sat 05, 2021 10:04 pm 
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Is it possible that your 80 tube was not the original? Maybe it came from some other place

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 Post subject: Re: #83 tube
PostPosted: Jun Sat 05, 2021 11:19 pm 
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Location: Elmira, NY
Barry H Bennett wrote:
Is it possible that your 80 tube was not the original? Maybe it came from some other place

I’ve had this tube tester for 45 years and it always worked since every I bought it (used). I never changed the tubes, I think the plating just deteriorated, maybe defective from the start. Just recently the gm meter failed due to rust flaking around the magnet. When I had it apart to replace the meter I noticed one of the anodes of the #83 tube looked odd.


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 Post subject: Re: #83 tube
PostPosted: Jun Sun 06, 2021 2:12 am 
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The 83 in my 800 just shorted out a few days ago. Flakes on one plate. Dim filament. Line adjust don't work. Fuse light lit up bright and any tube tested. Replaced with good used 83 all is good again.


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 Post subject: Re: #83 tube
PostPosted: Jun Sun 06, 2021 4:41 am 
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Curious if it’s the same plate failing for everyone?

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 Post subject: Re: #83 tube
PostPosted: Jun Sun 06, 2021 10:47 am 
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I'd imagine it has something to do with the number of tubes a given tester has tested over it's lifespan.... but if you stop to consider that most of these 83 tubes are upwards of 70 years old.... that's not really bad ;-) Most of us have a "plate or two" failing at our age. :mrgreen:

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 Post subject: Re: #83 tube
PostPosted: Jun Sun 06, 2021 7:58 pm 
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Located my B&K's 83, flakes are from outer portion of plates that face inward. Sides toward glass appear normal. Tube branded Dynascan, 1972 code date, manufacturer RCA.

Today in the Precision 912 tests fine, nearly equal emission from both sides. Orig mounted horiz in 707, was very unhappy. Testing tubes, one side fired maybe 50% of time. Also gave similar results when tested in the 912. Dunno if it makes difference, last five years stored in a near vertical position.

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 Post subject: Re: #83 tube
PostPosted: Jun Sun 06, 2021 8:09 pm 
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Location: Auburn, AL
Storage position seems less important than the position when the mercury vapor cools. I’m surprised they’ve lasted as long as they have being used horizontally.

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 Post subject: Re: #83 tube
PostPosted: Jun Mon 07, 2021 7:47 pm 
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Location: Elmira, NY
The Saga continues. Today I received another #83 from an E-Bay seller. He said it was NOS, and I have no reason to doubt him. There were no Mercury splatter, but there is evidence of deterioration of the black oxide on one anode. It's the same anode as my original tube, but not too/as bad.
I'm beginning to suspect this is a characteristic of all #83's made.

I'll replace my original. I hope this one is better. As mentioned before, maybe this has no effect on operation, especially in a tube tester.

Maybe others will chime in and we can get more data.


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