Haier TDVCF2016, Service Manual

Page: 37 / 46

Color Television Model
：
20S62(TDVCF2016)
3854
2. curcuit explanation
(1)power curcuit
In this set, the power curcuit uses STR-W6735, which is produced by Fairchild Company.
AC 120V voltage is input through the power line and goes through power filter L801 to the commutating bradge curcuit. After
commutated by D801\D802\D803D\D804, the DC voltage is got by C804. This voltage is equal to 1.4*AC input. If the input
voltage is 120V, then the voltage of C804 will be 168V. Through the primary coil of T801 and L802, the voltage connect to P1
of STR-W6735.
STR-W6735 has crystal oscillator in it. It can control the switching of the MOS curcuit in it automaticly. P4 is apply VCC voltage
for STR-W6735. The voltage is provide by R802 from AC voltage when the power line is first insert. R802 is named start-up
resistor. After starting up, the VCC voltage is provided by primary assistant coil of T801. The voltage is borned at P3 of T801
and goes through R805\D805 to P4 of STR-W6735. After D805, the DC voltage is got at C810. The voltage of P4 of
STR-W6735 is desired to between 9.7V and 27.7V. If the voltage is less than 9.7V, the STR-W6735 won
’
t start up. If the
voltage exceeds 27.7V, the overvoltage protection curcuit in STR-W6735 will operation and the working of STR-W6735 will be
stopped.
P5 of STR-W6735 is overload protection pin. Through the C807, the overload protection will operation.
P6 of STR-W6735 is feedback pin. STR-W6735 will adjust the working state according to the signal from the photocoupler.
P7 of STR-W6735 is overcurrent protection pin.
P4 of STR-W6735 provides VCC for inner control curcuit. After the control curcuit has started to work, the inner MOS transistor
will open and close according to the control curcuit. Then the DC voltage at C804 will go through the primary coil of T801 to
GND. The current will increase or fall linearly. Then there will be voltage at secondary side.
P10 of T801 is the voltage of +B . It is used for horizontal scan and +33V for tuner. The photocoupler samples from +B voltage
and the STR-W6735 will adjust its working according to the feedback of the sampling.
P12 of T801 is the voltage of 11V. This voltage is used for SW +9V. At the same time, it provides photocoupler with VCC.
P13 of T801 is the voltage of 6.5V. This voltage is used for SW +5V.
P11 of T801 is the common GND of P10\P12\P13.
P14 of T801 is the voltage of 6.5V. This voltage is used for DVD +5V.
P15 of T801 is the GND of P14.
P16 of T801 is the voltage of 16V. This voltage is used for VCR motor\DVD +12V\horizontaol LBT(T402).
P17 of T801 is the voltage of 13V. This voltage is used for sound amplifying curcuit.
P18 of T801 is the common GND of P16\P17.
(2) DVD function problem
D812 on power board provides VCC of DVD +5V. AC voltage is supplied by transformer T801. R822 is a protection resister.
After D821, DC voltage is got at C816. I808 is a manostat for DVD +5V. It has a control pin to switch the +5V of DVD. The
control signal comes from the CPU on main board through the line of P806.
+5V is uses for DVD motor rotating and inner decoding curcuit.
If the R822 is a resistor of RF10-2W-0.27
Ω
-J-05-C, when the CRT is POWER OFF during the DVD loading, the DVD will not
work at the next POWER ON. When the set is POWER ON next time and changed to DVD mode, there will be no picture or
abnormal picture. One method is to take off the power line and then insert it back to the power socket again. If the method is
not accepted by user, a jumper to shorten R822 can solve the problem forever. Use a jumper and jointing it to the 2 sides of
R822. The products of first order have this problem. R822 is changed to a fuse resistor in the after production. So the after
productions have not the problem.
I807 is a manostat transisitor for DVD +12V. The voltage comes from D813 on the power board. +12V is used for DVD as