[R-390] Re: maintenance

[Scott Bauer]

 Hi Sir,

 Yes, you did help. In fact That is what I was thinking.Surge. Though I 
do not
have the experience that you do, it was my guess. There were some tubes
that may have lasted a little longer but all in all, they were bad.
 The un-effected tubes were 2-26Z5W,2- 6082, 3TF7, 1 6AJ5, 1 6AK6,
2-5651, 3-6C4.

 The radio did play the way it was but there is a noticeable difference 
in the
performance, more background noise. Better ssb reception, better audio
quality, better selectivity and sensitivity. Lets just say I got an 
overhual.

 Thank you very much Sir.  Regards, Scott

 Thanks to everybody else for your input as well.

 Scott
 

W. Li wrote:
> 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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