Service manual

Power BOARD
is NG
Power on and check whether there are 5VS, 5V and 24V
Check whether the connection of DB1 and DB2 is ok, whether DS
pin of JM1, C33 and C27 is in short circuit state.
Check whether the fuse is burn out
Yes No
Detailed operation Detailed operation
Check the DB1 and DB2 with the help of multimeter
“diode” function, if NG, please replace DB1 and DB2
If the DS pin of JM1 is in short circuit state , check
whether the diode of D3、D8 is in short circuit state, if
yes, replace D3 and D8, if not, replace JM1
Check whether D1 and D2 is in short circuit state, if
yes, replace them; if not, check whether the shunt-wound
resistance of R81 and R82 is 0.33 ohm, if not, replace
them.
Check whether the 3rd pin of U1,which is related with
JM1 PFC is 33 ohm, if not, please replace the resistor
then check it again, if still not ,please replace U1;
Check whether 12 and 13 pin of U1 is in short circuit
state,if yes, replace U1.
Check whether C27 is NG, if yes, replace C27, if not,
please check whether DS pin of JM2 and JM3 is in short
circuit state, if yes, replace JM2 and JM3;
Check whether D18 and D40 is in short circuit state, if
yes, replace D18 and D40;
Check whether R83 is 0.5 ohm，if not, replace R83，
Check whether R33 is 200 ohm，if not, replace R33 then
check if the resistance between 9 pin of U1 and ground is
200 ohm, if not ,replace U1；
Check whether there is a short circuit between 11 pin of
U1 and ground, if yes, replace U1. If JM1 and JM2 is
not in short circuit state, check the other related circuit.
Check whether C13 is in short circuit state, if NG,
replace C13;
Check whether the the pin 6/7 to pin 1 of U2 is in short
circuit state, if yes, replace U2.
Check whether the related circuit D6 and D7,which can
make U2 abnormal is ok, if not, replace D6 and D7.
Check whether the related cable layout is burnout.
Check whether there is 5VS，if none, check whether the circuit of U2 and
T4 etc have problem, especially all pins of U2 is in short circuit state,DB1，
D6、D7、D13。
If there is 5VS， press STB button to power on, check whether there are 5V
and 24V, if not, please check whether 5V,24 ,+12V and -12V is in short
circuit state to the ground.
Check output
circuit
Check whether there is AC voltage to 2nd and 3rd
pins of DB2, if not, confirm whether the voltage
5 V and 24V rise ,but fall to 0V rapidly.
If yes, check the feedback circuit of U7 and U5 or
the over-voltage protecting circuit which is made
of D26, D30.
If not, check the 11 pin of 4800(PWM output) ,
the latter circuit and the U3 circuit of
FS7M0880 . When there is voltage the 2nd and
3rd pin of DB2 , check whether C27 has 380V, if
yes, check the 11 pin of U1( PWM output), the
latter circuit and the soft startup circuit of R65
,related to U3 . if not, check the 4800 PFC circuit
of U1 and its PWM circuit.
Yes No
11.2. Power Board
118