Haier TDVCF2016, Service Manual

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Color Television Model
：
20S62(TDVCF2016)
3954
sound amplifying VCC. If the +12V is not available at P805, the sound out of speakers will be very small in DVD mode.
(3) degaussing curcuit
At P806 on the power board, there is a RLY.ON signal. After POWER ON by remote controller, there will be a high voltage on
the RLY.ON. Then the BE of Q806 will be turned on. The CE of Q806 will also be turned on. Then the relay will be turned on.
There will be current through the degaussing coil. Degaussing curcuit operates.
(3) Horizontal and Vertical scan curcuit.
After CVBS signal has been received at P52 of LA76834, there is SYNC seperation curcuit integrated in I501. Horizontal pulse
signal is got at P30 and vertical pulse signal is got at P26. P29 is AFC filter for horizontal curcuit and P33 is flyback pulse
signal from FBT. P28 is VCC pin for horizontal pulse decoding curcuit and P53 is VCC pin for vertical pulse decoding curcuit.
P31 is horizontal GND and P49 is vertical GND. P20 is related to vertical size comparation. P27 is for vertical ramp ALC filter.
LA76834 sends out horizontal SYNC signal to I701 at P37 and vertical SYNC at P36. The CPU will send out RGB signal of
OSD to LA76834 when it receives the H SYNC and V SYNC. If there isn
’
t SYNC signal, the CPU will not send out RGB signal
of OSD.
Horizontal pulse signal is converted to power board through the line of P808. After R401, the signal is amplified by Q402.
M16V provides horizontal inspiriting VCC through Q804 to LBT(T402). After amplified by T402, the horizontal signal can drive
the horizontal transistor Q401. Q401 provides horizontal switching through FBT and +B voltage is used. Then linear current is
produced on the H-DY.
At the same time, saveral DC voltages appear at FBT.
(1) High voltage is about 27KV, used for CRT.
(2) VIDEO voltage is about 180V, used to amplify RGB signal on the CRT board.
(3) 24V voltage is used for vertical scan cuicuit.
(4) HEATER is AC voltage for heater of CRT.
(5) ABL signal is connected to main board through line of P808 after sampling resistor R414(1Kohm). LA76834
will adjust the output RGB range according to the ABL voltage at P11.
Vertical signal is converted to power board through the line of P808. After R301, the signal is send to P1 of LA78041(or
LA78040). 24V voltage is provided at P2 of LA78041 by FBT and out VCC can be got at P6 through a diode D303. Reference
voltage is got from 24V by R303 and R304. R316 and R 314 can adjust the vertical center. There are 3 methods as follows.
(1) Use only R316(1kohm or 2.2Kohm), the vertical center is highest.
(2) R316 or R314 not used. The vertical center is in the middle.
(3) Use only R314(1kohm or 2.2Kohm), the vertical center is lowest.
Vertical scan signal is output at P5 of LA78041 to V-DY.
(4) RGB amplifying curcuit.
RGB VCC is provided to LA76834 through R511 at P16. Then RGB signal is output at P17/P18/19 and connected to CRT
board through the line of P902. RGB signal is amplified by transistor of Q901/Q902/Q903. 11V at P901 is used to provide E
DC voltage for Q901/Q902/Q903. 24V voltage is used to bring white screen on the CRT when power off. The capacitor C905 is
charged when power on and the voltage on the B of Q904 is high than E, so the CE of Q904 is not turned on. When the power
is turned off, the 24V voltage becomes to 0 and the voltage on C905 is still high. So the EB of Q904 is turned on and the EC is
turned on. High voltage goes to RGB electron gun, so white screen appears on the CRT.
Heater voltage is connected to CRT board by line of P901. Through R922, the voltage heats the CRT.
(5) Signal decoding process .
(a) at TV mode, mono sound signal.