Hitachi 51S700 proj. tv - fan quit shutting off

[frenchy]

I just noticed yesterday that the internal cooling fan (some teeny
little whining fan in there, to cool a cpu chip or the circuit boards
in general I assume) has stopped turning off when the set is turned
off. The fan just stays on as long as the set is plugged in.
Unplugging and replugging it in - fan just comes on again. Before
this the fan always quit when the set was switched off.
Is there any harm in just ignoring this? Other than that it's still
works flawlessly with perfect picture, no burn-in, I adore this set.
It is a #51S700 Ultravision set, I bought it new in 2003. Thanks!

 

[D Yuniskis]

frenchy wrote:

I just noticed yesterday that the internal cooling fan (some teeny
little whining fan in there, to cool a cpu chip or the circuit boards
in general I assume) has stopped turning off when the set is turned
off. The fan just stays on as long as the set is plugged in.
Unplugging and replugging it in - fan just comes on again. Before
this the fan always quit when the set was switched off.

Are you sure that it "quit" *exactly* when the set turned off
(and not "shortly thereafter)?

The fan can either be wired directly to *a* power supply
(likely one that goes on and off with the set's "power")
or to a temperature sensor that runs the fan in demand mode
(often using a power supply that is available regardless of
the set's "power"). The latter can be done by a dedicated
"fan controller" (e.g., a thermistor and a transistor)
*or* by a microprocessor in the set (using temperature
information from <wherever> or simply running the fan
open-loop -- whenever the set is powered on).

Is there any harm in just ignoring this? Other than that it's still
works flawlessly with perfect picture, no burn-in, I adore this set.
It is a #51S700 Ultravision set, I bought it new in 2003. Thanks!

Depending on the quality of the fan and your housekeeping,
the fan may end up failing prematurely. This could either
cause the fan to stop rotating -- which will probably
result in your set failing (the component being cooled
will overheat) -- or, for the fan to get quite noisy
(which you will complain about).

Hard to say for sure without having schematics for the set
(or another set to observe).

 

[frenchy]

Are you sure that it "quit" *exactly* when the set turned off
(and not "shortly thereafter)?

Absolutely sure that it always immediately shut off when the set was
turned off.
Thanks, I guess I will just let it run and wait for it to fail or get
noisy, if it does, and hope I don't have the set that long : )
Frenchy