Audio Circuit; Audio Input; Audio Output; Power Supply - NEC NMV 1700V Service Manual

1. Audio circuit (Circuit diagrams Main PWB 1/1 JACK PWB 1/1)
1.1

Audio input

The audio signal input recei ved from the audio input terminal (JK011) is applied t o the pre-amplifier I006 of
2 (L-CH) and 29 (R-CH) through the low-pass filter consisting of R047, R049, R048, R050, C062 and C063.
In this pre-amplifier, controls of Volume, Balance, Bass, and Treble are conducted. The audio signal controlled
at the pre-amplifier is entered in and amplified at the AMP I007 of 9 (L-CH) and 1 (R-CH). Since then, the signal
is to the output jack.
1.2

Audio output

The audio signal is output from the output terminal (P012) of the jack to the speaker system.
2. Power supply (Circuit daigrams MAIN PWB 8/10, 9/10, 10/10)
1. I322:DC-DC converter
A 5V power supply for LCD modul e, CPU, and logic is generated from the 19V source.
2. I323:3-terminal regulator
A 3.3V power supply for Scaler IC I315, LVDS IC I319, I320 is generated from the 5V source.
3. I330:3-terminal regulator
A 3.3V po wer supply for SDRAM IC I316, I3 17, I318 is generated from the 5 V source.
4. I324:3-terminal regulator
A 2.5V po wer supply for Scaler IC I315 is generated from the 5 V source.
Q307, I321 ON/OFF control for LCD Module
ON/OFF co ntrol is performed for power ON/OFF and also for t he power saving sequence.
3. Video input circuit (Circuit diagram MAIN PWB 4/10)
The analog video signal input entered from P304, the AC-coupled video signal is used to clamp the black level at
0V).
4. Definition converter LSI peripheral circuit (Circuit diagram MAIN PWB)
I315 gm5020 is the definition converter LSI.
The analog R, G, B signal input entered from the video input circuit is converted into the digital data of video
signal through t he incorporated A/D co nverter. B ased on thi s conversi on, this device performs interpo lation
during pi xel ex tensio n. The source vol tage for thi s devi ce is 3.3V, 2.5V and th e syst em clo ck frequency is
24MHz. The withstand voltage level for the input signal voltage if I315 is 3.3V and 5V.
5. System reset, LED control circuit (Circuit diagram MAIN PWB 3/10)
5.1 System reset
System reset is performed by detecting the rising and falling of the 5V source voltage at I301.
5.2 LED control circuit
Green / amb er is lit with the control signal of the LED GREEN and LED AM BER signal pin 15, 1 2 from I306
(Circuit diagram MAIN PWB 2/8).
6. E PROM for PnP (Circuit diagram MAIN PWB 4/10)
2
Circuit Description
N MV 1 7 0 0 V
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