[R-390] 6080 in place of 6802 - RMS ???

[James Miller]

You know I just tried this (threw my back out again, darn it) and I see
the strangest effect when viewing the ballast tube in the glow of the
color TV.  The long slender filament actually seems to be vibrating,
like a wave.  Yes the phase locked TV scan frequency is a little
different than the line frequency, so this aliasing effect is clearly
noticable.  Could this 60 Hz vibration of ballast tube filaments be the
cause of premature failures?

mikea wrote:
> 
> On Wed, Jan 09, 2002 at 05:49:47PM -0500, James Miller wrote:
> > And what about the changes in filament resistance as a function of
> > temperature caused by pulsating filament current?  Would the filament be
> > cooler on average, hence having a lower resistance on average, further
> > compounding the problem?
> 
> A simple (though perhaps rough on the gear) experiment will
> demonstrate how long is required for the filaments and cathodes
> f most tubes to cool down. Simply power it down, count three
> seconds, and apply power again. It'll probably come right up.
> 
> Another way is to view the filaments by the light of a TV set,
> at 30 (or is it 60) half-frames per second. If the filaments
> appear to get brighter and dimmer, it's due to stroboscopic
> effect, as the power line frequency isn't going to be exactly
> 60 Hz, though it may be within a few parts in 10K. At any rate,
> if there _is_ a stroboscopic effect, the filaments are cooling
> down near the zero crossings.
> 
> Betcha you won't see it.
> 
> --
> Mike Andrews
> mikea@mikea.ath.cx
> Tired old sysadmin since 1964
> _______________________________________________
> R-390 mailing list
> R-390@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390