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Author Topic: OA2 regulator  (Read 5859 times)
W2WDX
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Posts: 188




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« Reply #15 on: April 29, 2012, 07:08:46 PM »

I think the original post speaks more to the tester than the tube.

If your gonna use a tube tester, especially an old one, use a Hickok. (I use an Amplitrex Digital built in 2010.) The Heath's (ALL OF THEM) are far from accurate, give erroneous results on some specialized tubes (as you just experienced) and have many mistakes in its published charts.

I don't care who says it's "approved", obviously whoever approved it knows little about tube testers in general. The Heath's are all emission only testers and tell nothing of the tubes performance using real world voltages and current draw in working circuits. A tube could measure good on a Heath and not work properly in a circuit. Or at least perform weakly.

Just my opinion ...

John W2WDX
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AA4HA
Member

Posts: 1434




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« Reply #16 on: May 02, 2012, 12:35:21 PM »

Depending upon the radioactive isotope used, eventually all OA2 tubes will fail when they cannot ionize to start up. A few years ago I ran across a reference regarding this with all tubes that have a miniscule amount of radioactive materials inside of them. Some isotopes have already gone through several "half-lives" and may be approaching that point in time where they will not strike up and act like regulators.

The element and amount varies by tube type and manufacturer. For a more definitive reference;

http://www.tubecollector.org/documents/radioactive.htm
« Last Edit: May 02, 2012, 12:41:14 PM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
G3RZP
Member

Posts: 4567




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« Reply #17 on: May 02, 2012, 01:44:11 PM »

i don't think all VR tubes have radioactive isotopes in them. Certainly no suggestion for VR105s and VR150s. Not sure about ALL 0A2s
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G8HQP
Member

Posts: 123




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« Reply #18 on: May 02, 2012, 02:02:13 PM »

I think most 0A2s don't have any deliberate radioactivity in them. For those that do, once the activity declines due to age you will just have to rely on ambient light or natural radiation to help them fire - just like those which never had any help to start with. The firing voltage may be a little higher and a bit variable but in most circuits they should still be OK.
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KD0REQ
Member

Posts: 932




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« Reply #19 on: May 02, 2012, 03:24:53 PM »

you can always (and someday we will have to) hook a pilot lamp or an LED across the filament of a nearby tube and shine it on the VR tube.  generically a gas tube needs some spike or ambient stimulation to overcome the initial state of the gas and get it to fire.  things like thyratrons have a trigger element.  unstated in the use of VR tubes is that until current is drawn, the no-load voltage of that supply on them kicks over the trigger voltage and gets the gas to conduct.  at that point, of course, the load can now see and draw power, at least the minimum in the specs, and keep the tube lit.  a little ionizing radiation can be that spike in a dark sealed chassis.
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N9LCD
Member

Posts: 170




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« Reply #20 on: May 03, 2012, 02:12:01 PM »

I pulled a spare green-ink Sylvania 0A2WA out of stock.  The legend reads:

  "THIS TUBE CONTAINS LESS THAN 0.03 MICROCURIES OF KRYPTON 85"   
 
  The tiny "RADIOACTIVE" symbol is "green".

  Krypton85 has a half-life of 10.756 years. 

   The "average" starting current for an 0A2 is 75 mA averaged over 10 seconds.  The   
   RCA manual states that this must be followed by a steady-state operating condition
   of at least 20 minutes, or tube performance will be impaired.

N9LCD

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