Quote:
Originally Posted by NewVista
filaments light nice deep red (meaning air not a problem ? as I would expect warmer orange color with air present ?)
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Sounds to me as if the tube has become gassy.
What happens is the gas conducts heat away from the filament, and causes it to run cooler, hence the darker/dimmer red color. Now this may seem bass ackwards, but the heater is more likely to burn out when it is running this way because the resistance of the cool heater is much lower than when it is at normal operating temperature, so that it will blow out like a fuse that has excessive current running through it.
sad,
jr