[R-390] More Ballast Tube Noise

[N4BUQ at aol.com]

How do you "change a tube radio"?

Barry(III) - N4BUQ

>I don't know that's such a great bargain.  I have a couple of 3TF4's around,
>but never tried them.
>
>There is a document on the Amperite web site which includes the following:
>
>"LIFE EXPECTANCY:
>Average life if operated as recommended 2000 hrs.
>If operated continuously at maximum voltage 1000 hrs.
>If operated continuously at 80% maximum voltage 5000 hrs.
>If filament is operated below glow point 5000 hrs. and up
>
>In operation, the Amperite filament starts to glow at one point; as the
>voltage is increased, the glow spreads over the entire filament. Like
>incandescent lamps, turning the ballast tube on and off reduces its life,
>especially if operating near its maximum voltage."
>------------------------
>
>So, there's quite a range -- and they recomment operating below the glow
>point.  The differential is such that a $9 glowing 3TF4 might not compare
>well -- if you need 3 or more of them vs. a 3TF7.
>
>There are some other interesting things in that document, such as:
>
>"GENERAL ADVANTAGES
>
>. Light, compact. No moving parts
>
>. Rugged, will stand vibration of 10G minimum
>
>. Hermetically sealed; not affected by altitude or humidity changes
>
>. Can be changed as easily as a radio tube
>
>. Operates equally well on A.C. or D.C."
>
>Hmmmmm.... hermetically sealed..... 10G's!  ... a bargain at twice the
>price.
>
>Finally, that doc also says "It (the ballast tube) consists of a resistance
>wire with a positive temperature coefficient of resistance, hermetically
>sealed in a bulb containing hydrogen or helium gas."
>
>So, apparently there are von Hindenburg and Non-von-Hindenburg renditions.
>
>You can read the whole thing at http://www.amperite.com/Uploads/Ballasts.pdf
>
>Barry
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>----- Original Message ----- 
>From: <doorbar61 at tiscali.co.uk>
>To: <r-390 at mailman.qth.net>
>Sent: Wednesday, February 09, 2005 5:35 PM
>Subject: RE: [R-390] More Ballast Tube Noise
>
>
>
>hi, just as a matter of interest about 7 weeks ago i purchased on uk ebay
>2 3tf4 ballast tubes both are nos for $18 the pair. i put one in my 390a
>whicth i use most days and so far it is fine, sure it glows alittle more
>red but is this another and cheaper way to keep the 390a running, yours
>brian
>
>
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