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NotTaR of Television Sets : About instant-on TVs
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1994-2007, Samuel M. Goldwasser. All Rights Reserved. Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied: 1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.
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Most TVs built since, say, 1980 have only the microcontroller
powered from a small transformer when the set is off. This permits the
remote control or front panel pushbutton to switch the set on. This circuitry
should be no more prone to catastrophic failure than what is in a VCR or
digital clock.
Historically, there were 'instant on' TVs which kept a substantial portion
of their circuitry live all the time - especially those using vacuum tubes
in at least part of the circuitry (other than the CRT). In these, there
was a lot more to fail. Those tubes would continue to change their
characteristics for many minutes when warming up. Circuits were also much more
touchy - remember all that constant tweaking! Thus, it made sense from
the users's perspective to eliminate the warmup period and keep those tubes
toasty all the time.
In modern solid state TVs, the only component to really need a warmup period
is the CRT. All this means is that you have to wait 20 seconds for
the picture to appear.