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

[mikea]

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