[R-390] re: maintenance

[David C. Hallam]

I live in Florida and have a R-390 with a Johnson Invader 200 and a HB
4CX1500A amplifier.  I don't leave any of them on any longer than absolutely
necessary.  With the heat from fans on the 6082 series regulators in the
R-390, the 6146 finals in the Invader, and the 200 watt filament dissipation
of the 4CX1500A, even the stand-by load is too much for my AC system in the
shack.  Maybe in mid January in up state New York the heat would be
appreciated.  In Tampa it's too much any time.

David
KC2JD/4

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of W. Li
> Sent: Thursday, June 21, 2007 11:43 AM
> To: odyslim at comcast.net
> Cc: R-390 at mailman.qth.net
> Subject: [R-390] re: maintenance
>
>
> I think that you must be a victim of a *surge*. Vacuum
> tubes do not tolerate overvoltage or mechanical trauma
> well. Operating them at design voltages in a stable
> environment is the best way for a reasonably long life
> of 10,000 hours (1.14 years if left on 24 hours a
> day).
>
> Adding a cooling fan in hot environments is a very
> good suggestion.
>
> Bill Kleronomos wrote a real good article in ER in
> 1994 (vol 66 page 10) entitled *Electron Tube Survival
> Primer*. Perkins Electro Acoustic Research lab in
> Canada ran some tests in which they found that running
> a 6AK5W at an envelope temperature of 100˚C
> resulted in a 50% tube survival at 5000 hours, but 80%
> failed by 2000 hours if run at 253˚C. In the same
> article, they found running heaters at 5.04VAC gave
> the longest life (albeit at lower emmisions); running
> at 6.30VAC had a 85% 5000 hour survival, but running
> them at 7.56VAC led to a 20% 5000 hour survival.
>
> Hope this helps.
>
> W. Li
> Mercer Island, WA
>
>
>
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