NEC PX-50XM4, Service Manual

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Operation in each CPU block:
• For the purpose of signal changeover via the Extension Port IC based on the input mode, the Video SW and the Video/sync SW are set up.
• For the purpose of audio control (sound volume, balance, and sound quality), the audio control is set up.
• For the power control, power ON/OFF control is conducted for the Power unit.
• LED lighting is set up.
• The key codes are received from the Key control circuit. The key codes are A/D converted in the CPU for code recognition.
• The thermal data from the TEMP IC are received at the CPU. Based on these thermal data, the fan driving voltage is controlled via the Extension Port IC to regulate the fan speed.
• The remote control codes are received from the Remote Control.
• Communication is maintained with the external equipment via the RS232C control block.
• When the power supply is turned on, the CPU is reset with the reset signal sent from the RESET IC.
• During timer function control, the time-related information is received from the RTC IC. At that time, present time is also set up.
• According to the input signal, setting is made for the module. Based on the APL information, brightness control is also carried out.
• During the OSD display, the OSD display data and the OSD position data are set up for the OSD IC.
• Various setup data (input mode, power ON/OFF status, setup values of various user controls, and so on) are stored in the E2PROM.
• For each signal mode, the signal frequency division ratio, clock phase, and signal level are set up for A/D1,2.
• For motion picture signals, the D/A-converted DC voltage information from the CPU is put in the LPF 1,2 in order to set up the cutoff frequency.
• For the purpose of video signal processing (I-P conversion, scaling, gamma correction, and others), the digital signal processing block is set up for each input signal.
• Color system identification is performed by the Video chroma decoder and setting is made based on the color signal for the Video chroma decoder.
• A changeover action is taken between the closed caption mode and the text mode for the CCD IC.
Alarm detection:
• Temperature alarm
If the correct thermal data are not transmitted from the TEMP IC control circuit to Pin 2 (IC2 data) and Pin 1 (IC2 clock) of the TM connector (in such a case, [-] appears in the
column of the any temperature sensor T1 ~ T3 where FAN SET is faulty in the service menu), the CPU identifies this condition as a fault in the temperature sensor PWB and
causes the LED to blink in green at the intervals of approximately 2 seconds so that the power system can stay in the standby state. In addition, if the internal temperature of the set
should exceed about 75°C the LED makes [blinking in red] and the power supply assumes the standby state. To reset the alarming condition, it is necessary to turn [OFF] the main
power circuit of the set main unit once and then turn it [ON] again. When the temperature inside the set should exceed the levels specified below, the LED makes [blinking in red]
and the power supply assumes the standby state. To reset the alarm condition, it is necessary to turn OFF the mains power supply once in the main unit and turn it ON again.
42VP5/VM5/VR5: Approx. 95°C, 42XM3/XR3: Approx. 82°C, 50XM4/XR4: Approx. 80°C, 61XM3/XR3: Approx. 75°C
CONFIDENTIAL
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