[AMRadio] AMRadio Digest, Vol 121, Issue 15..the 0A2


Poli, Louis (US SSA) louis.poli at baesystems.com
Tue Feb 25 17:49:11 EST 2014


Jim;

Thanks for sharing; as I hadn't known if any others had the design.
And I hadn't read before of this additional consequence of the design; in that a smoother rise vs. over-shoot behavior, would lessen other issues.

Now I have hundreds of tubes in my holdings; including specialty tubes, and of course a number of the 800 series industrial tubes. 
Some I couldn't resist buying because it was the end of a hamfest day, and the guy yelled "give me  dollar" for the box full of them. Others are "finds' that you get by making a deal with the guy in the early morning set up at the hamfest, and scarf up a number of unusual types.
 But on only one of the NOS military tube boxed devices like this, specifically an 0C3, was there an ink stamp on the box warning that the device was radioactive. 
Thorium in the thoriated filaments in rcvr and power xmitter tubes, will register on the Geiger counter

True, not dangerous, but curious that the stamp is not more prevalent.

Now I make it a point to use tube type/historical equipment for my hobby and its testing/maintenance. 
The HV power supply mercury vapor rectifier tubes, notably the 872, 8008, but the more common to the amateur 866A types (that I use) can suffer from the noise and oscillation issues.
As you know, they have a lot in common with the regulator tubes and also have a small fixed voltage drop. 

But evidently, word of mouth from people even older than me, has it that under certain reasonably rare conditions, a significant blow back arc can form which could melt/explode the tube and splatter mercury and glass. And to additionally include that the UV blue glow may be intense enough to damage eyesight.
However, all the RCA (and other) receiving/transmitting tube Manuals included application chapters; note that noise may indeed be seen, but a that choke type or shielding solution could cover this.
Physical damage and UV radiation are not mentioned.

As an amusing anecdote, I had read in one of my archaic (this one circa 1929) engineering texts on tube technology; that the state of the art and proper maintenance, had now limited these potentially dangerous blow backs to less than once a month in the Power House. 
These were metal or glass/ceramic very large Hg rectifier tubes, that looked something like 55 gallon drums and were under continual vacuum pumping. They could handle megawatts, and applications included powering passenger trains.
Now having said all of this, I proceeded to put a piece of clear plastic between me and the tubes to stop the UV, but all else remains as it is. 

Let me invite other reflector members to share any dramatic experiences they have had with final amplifier or support tubes in their vintage AM rigs. 
Surely a modulator or PA tube, must have blown up somewhere.

Best regards,
Louis  N3OL

-----Original Message-----
From: james.liles at comcast.net [mailto:james.liles at comcast.net] 
Sent: Monday, February 24, 2014 9:36 PM
To: Poli, Louis (US SSA); amradio at mailman.qth.net
Subject: Re: [AMRadio] AMRadio Digest, Vol 121, Issue 15

Hi Louis:

I have some some Sylvania OA2's that are radio active.  The difference in behavior is there is no over shoot at turn on.  They transition smoothly at exactly the same voltage.  I believe this enables them to tolerate some filtering without oscillation.

Kindest regards Jim K9AXN



-----Original Message-----
From: Poli, Louis (US SSA)
Sent: Monday, February 24, 2014 11:32 AM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] AMRadio Digest, Vol 121, Issue 15

Jim;

All you need do is measure the DC voltage at the pins.
It will regulate it very well, and there are only two pins used in these tubes.

The 0A2 will measure at 150 Vdc, and the 0B2 will measure at 108 Vdc.
I think the orange glow is of the 0B2 type; however if they were designed to use the same gas then they will have the same color.

But no issue, look up both these at Franks' electron tube pages.
It will be Frank dot Pocnet dot net.

All the tubes beginning in zero are this class. There aren't many.

Check the Base diagram of any you look at.
Some are full size octal base types; like the 0D3 and 0C3.

Here is a little bit of trivia.
The 0C3 is slightly radioactive.

To fire a plasma in tubes like this; reliability was greatly enhanced if you put a trace of a radioactive gas in the envelope too. I think it is a radioactive isotope of helium.

The radiation (alpha/beta particles) emitted will constantly keep the other gas slightly ionized; so turn on was quite reliable.

Regards,
Louis

-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of amradio-request at mailman.qth.net
Sent: Sunday, February 23, 2014 12:00 PM
To: amradio at mailman.qth.net
Subject: AMRadio Digest, Vol 121, Issue 15

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Today's Topics:

   1. Tube ID (Jim Wilhite)
   2. Re: Tube ID (Rob Atkinson)
   3. Re: Tube ID (Larry Szendrei)
   4. Re: Tube ID (Rob Atkinson)


----------------------------------------------------------------------

Message: 1
Date: Sat, 22 Feb 2014 16:42:28 -0600
From: "Jim Wilhite" <w5jo at brightok.net>
To: "AM Radio Discussion List" <amradio at mailman.qth.net>
Subject: [AMRadio] Tube ID
Message-ID: <2039AD411845495EB68553640EEDFC00 at JimPC>
Content-Type: text/plain; charset="iso-8859-1"

I have a voltage regulator that is not marked except for the following: 
816B997.  In circuit it glows bright orange.

My memory fails me at the moment, is it an OA2?  It is a 7 pin miniature 
tube.

The OB2 glows a purple color but I forget what color the OA2 glows, or for 
that matter what this tube may be if not an OA2.

Jim
W5JO

------------------------------

Message: 2
Date: Sun, 23 Feb 2014 07:02:40 -0600
From: Rob Atkinson <ranchorobbo at gmail.com>
To: Jim Wilhite <w5jo at brightok.net>
Cc: AM Radio Discussion List <amradio at mailman.qth.net>
Subject: Re: [AMRadio] Tube ID
Message-ID:
<CALWD7Z5hoR_0gj2h3Bzw9sr+5TMaUSN9HbVFkB4REZfgsjpJZQ at mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1

Hi Jim,

I think I'd measure the voltage at that tube's socket and stick a known VR 
tube in there for that voltage and see what happens.  But, my knowledge is 
somewhat limited.  I guess a VR tube with neon in it
would glow orange.   5651 and 5651A are miniature neon VR tubes I
think.  90C1 or 85A2?

73

Rob
K5UJ

On Sat, Feb 22, 2014 at 4:42 PM, Jim Wilhite <w5jo at brightok.net> wrote:
> I have a voltage regulator that is not marked except for the following: 
> 816B997.  In circuit it glows bright orange.
>
> My memory fails me at the moment, is it an OA2?  It is a 7 pin miniature 
> tube.
>
> The OB2 glows a purple color but I forget what color the OA2 glows, or for 
> that matter what this tube may be if not an OA2.
>
> Jim
> W5JO
> ______________________________________________________________
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