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4. Svstem Contro)
To ensure correct and safe tamp illumination, [amp
rumination conditions are monitored to detect abnormal
temperatures in the iamp power source and to control
the cooiing fan. On the metai haiide iamp used, vottage
as high as 20kV is applied at striking to
initiate discharge. Once discharge commences, vott-
age stabiles at about 85V.
)n addition, the iamp aiso generates heat, increasing
projector interior temperature. A cooiing fan prevents
temperature increases. Cooling fan operation is con-
trolled by the CPU which monitors the iamp power
source to determine iamp illumination conditions.
Correct iamp rumination makes the tamp power
source send an "L" signal to pin 19 of the CPU (tC801).
if the tamp does not !ight or is suddenly extinguished, the
"H" signal is sent to pin 19 of the CPU (!C801). When the
tamp tights after the projector is turned on, the CPU
(tC801) starts chocking the input at pin 19 at 3 seconds
after projector turn- on. !f the "H" signal is received by
pin 19 for a duration of 1 second, the CPU (tC801)
evaluates this indications as an abnormal condition,
turning the power off automatically and initiating 1 -
minute thermal protection. While in protection mode, at!
set keys and remote control keys including the power
on/off switch witt not respond. The cooiing fan witi
continue to operate in protection mode.
The tamp power source temperature atso rises due to
control toss of the chopper (Q701) and tamp driver
(Q702- Q705). This makes it necessary to atso coot
down the lamp power source with the cooiing fan,
therefore the tamp power source temperature is also
monitored, tf the temperature of power source heat sink
reaches approximately 80 °C , an "H" signat is sent to pin
19 of CPU (tC801) ("L" signal for normal temperatures).
An "H" signal at pin 19 for a 1 second duration is
considered as abnormal. The projector automatically
turns off and the 1 - minute protection is initiated. Att set
keys and remote controi keys wiii not respond in
protection mode, but the cooling fan witt continue to
operate.
During tamp fighting, the discharge - induced heat
increases gas pressure inside the tamp. As gas pres-
sure remains high after tamp turn - off, the tamp cannot
be turned on again immediateiy. The 1 - minute protec-
tion is initiated again after turning off the tamp (turning
off the projector), disabting ait set keys and remote
control keys for that period. The cooting fan wiit continue
to operate until the gas pressure returns to a satisfactory
tevet.
The green LED indicates tamp monitor operation as
to) tows:
___
^NBy^
EBMshows tamp monitor flow chart.
— 6 —
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