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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: RE: Controlled warm-up option? posted by Eli Duttman on August 17, 2015 at 07:52:37:
Hi Eli,
What you said is sort of correct but not the whole story.
Series string heaters for the reason which you mentioned have been around since the 1930s, long before controlled warm-up tubes were thought of.
It turns out the resistance of the heater is a function of the temperature and therefore changes as the heater warms.
Before controlled warm-up, watching the tubes in a series string TV warm up was scary. Some would be dark and some lit like light bulbs until the whole mess stabilized. As you might expect the ones which lit like lights had a short heater life. GE would put Glo-bar resistors in series with the heaters to slow things down and mitigate the problem. Finally it occurred to someone to design the tube heaters to warm at the same rate when fed with the rated current. This took care of the heater warm-up issue but the cheap TVs were still death traps with their "hot chassis".
Phil
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Follow Ups
- RE: Controlled warm-up option? - coffee-phil 08:23:23 08/17/15 (0)
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