Akai LM-H17CLSA Service Manual page 30

9.3 Key、LED&IR Board Circuit
Refer to Key、LED and IR circuit diagram of PWB-0475 in Chapter10.2.
* Key : The Keyboard is connected with Main Board through socket P021 and wire
PA21 and to control the I012 (MCU) , so if the operation of key is fail , the I012
(MCU) may fail .
* IR : The IR01 (TSOP1138) is a receiver for infrared remote control systems. The
demodulated output signal can directly be decoded by MCU I012#15 through
P015#5 and wire PA01
* LED :The dual LED D001 on LED&IR Board is controlled by MCU I012 #24、#25
through P015 #2、#3 and wire PA01.
9.4 Inverter Board Circuit
The inverter board is fed with +12V through P017 #1、#2 on main board and
offers 10.5 mA (typical ) to each lamp of backlight in LCD panel.
The On / Off of the inverter is controlled by the voltage of P017 # 5 which is
applied from I019 (Scaler:TP6760) #95 (FPBACK). While the voltage of P017 # 5 is
'H'(2~5.5V) , the lamp of backlight will be turned on. While the voltage of P017 # 5
is 'L' (0~ 0.8V) , the lamp of backlight will be turned off.
Adjusting the Brightness in OSD menu is to control the voltage at #62 (DVD0) of
I019 (Scaler:TP6760) and then applies to P017 #7 (to Inverter ). The range of the
voltage is from 0.5V to 2.8V. If the voltage of P017#7 is 0.5V, the screen will get
light ; if it's 2.8V, the screen will get dim. It means that the different voltage will
change the lamp current through the inverter to make the screen lighter or dimmer.
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