Iiyama Vision Master Pro 451, Руководство по обслуживанию

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(3) SUB POWER circuit
When AC input is supplied to SUB POWER circuit, start-up resister R908 and R909 detect 4 pin of IC901voltage
(VCC-IN) and activate internal start circuit of IC901. When pin 4 of IC901 voltage turns to 16V, internal control circuit
starts operation and auxiliary coil voltage between 2 and 3 pin of T901 (sub transformer) is up to approx.18V, and
SUB POWER circuit is activated.
IC950 detects the load of 5V output voltage from the T901 secondary and controls the feedback current in PC901
(photocoupler) by fed back to 5 pin of IC951 (OCP/FB).
The T901 secondary provides the following DC voltages:
Q
8.5V line: Supplied to the Heater voltage IC (IC920) and the Audio-Amp (IC501) as power source.
R
5V line: Supplied to the Microprocessor (IC301 and IC104), USB-IC (IC701), SW-IC (IC101) and 5V
CONTROL circuit as power source.
Note : Above waveform is switching waveform when USB peripherals are not connected.
D901
IC901
IC920
AC-IN
90-132/
198-264V
T901
PC901
6.3V
1
8.5V
2
5V
IC901 pin 1 Drain output
(100V/div)
IC901 pin 5 OCP/FB input
(0.5V/div)
<Waveform>