[R-390] Tubes new or used?

[Bob Camp]

Hi

I agree that hydrogen is a bit unusual in a tube. I would have expected 
helium. In either case you probably don't have to worry much about an 
explosion. In order to explode you would need a bunch of oxygen in with 
the hydrogen.

Apparently they did a back fill of the tube in order to adjust it's 
characteristics. I would not be surprised if it was a tube by tube 
process. Something in the process must have made these expensive to 
build. The nice thing about hydrogen or helium is that you don't have 
to use a lot of it to get good thermal conductivity. Those little atoms 
move heat really well.

In any case - the ballast tread has been going on forever and ever. So 
far nobody has posted data showing the ballast tube makes the radio 
work any better. That includes the paragraph about the ballast tube in 
the original Collins project report on the radio.

As long as you do a plug in resistor mod I don't see any reason why 
that's a bad thing. Wrap the ballast tube up real well and store it 
away on the shelf. If you ever want to sell the radio as a  "100% real 
thing" then plug it back in.

	Take Care

		Bob Camp
		KB8TQ



On Feb 2, 2005, at 9:11 AM, Cecil Acuff wrote:

> I guess I missed most of that past discussion...but I certainly 
> wouldn't want any tube of mine to be full of Hydrogen.  If the 
> filament were to arc when it decided to open up I would expect an 
> explosion.  Sounds like the Hindenburg (spelling) all over again.  Are 
> you sure it was Hydrogen?  Maybe Nitrogen...
>
> Just seems strange to me.  Also if it escapes what does it leave 
> behind?
>
> You are also saying that Ballast tubes have a shelf life.....anybody 
> know how long that might be?
>
> Or maybe I have fallen off into a trap here.....hmmm
>
> Cecil...
> ----- Original Message ----- From: "Bill Hawkins" <bill at iaxs.net>
> To: "R-390 HF Receiver List" <r-390 at mailman.qth.net>
> Sent: Tuesday, February 01, 2005 10:35 PM
> Subject: RE: [R-390] Tubes new or used?
>
>
>> There's New Old Stock, which may be 40 years old.
>>
>> IIRC, in one of our frequent ballast threads, it came out that
>> the iron resistor in a ballast tube is cooled by hydrogen. Now,
>> hydrogen, being the smallest atom, tends to escape from anything
>> made of bigger atoms, which is everything including glass.
>>
>> So you need to be careful when you ask about "new" tubes. NOS
>> isn't necessarily what you're looking for.
>>
>> Oh, and hydrogen makes iron brittle over time.
>>
>> Just to kick over the can, unless you run your receivers from
>> poorly regulated field generators, you don't need a ballast tube.
>> And you don't need the heaters unless you alternate between
>> desert and polar regions with the same receiver. But if the set
>> was aligned with ovens on, it needs to be re-aligned with them off.
>> The calibrator oven needs to stay on.
>>
>> Regards,
>> Bill Hawkins
>>
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