Sharp LC-37XD1E, Service Manual

Page: 32 / 198

LC-37XD1E/RU
4 – 1
LC-37XD1E
Service Manual
CHAPTER 4.
TROUBLESHOOTING TABLE
[1] TROBLESHOOTING TABLE
Power unit operation check.
Are the power cord and har-
ness in the unit properly con-
nected ? NO Connect the power cord
and harness properly,
and turn on the power.
YES
Is F701 normal ? NO Are both ends of C704
and C715 short-cir-
cuited when checking
their resistance values? NO Replace F701.
YES
YES
C704
⋅⋅⋅
Check VA701 ,
VA702 and D701.
C715
⋅⋅⋅
Check IC704
and 705.
Is a voltage of BU5V applied
to pin (20) of P701?
(Set the main power SW to
OFF.) NO Is a voltage of approx. 8
- 15V to pin (4) of
IC705? NO Check IC705,
IC708, D725 and
Q724.
YES
YES
Check short circuit of 5V
line (D737, C752, etc.).
Is it a symptom that the relay
clatters twice as soon as the
main power SW is set to ON
and the power is not sup-
plied? NO Does a relay noise
sound? (Once) NO Are PCON1 and 2
[pins (1) and (2)
of P702] at Hi
(3V or more)?
YES
YES YES
Check peripheral cir-
cuits of D738, R828 and
D735. Check peripheral
circuits of Q712,
Q713, Q721,
Q723 and RY701. NO There is a possibility that control
by P-CON is not performed
properly. Check whether the
"PCON1" and "PCON2" signals
are sent from pins (A23) and
(A21) of IC3002 (V-PRO.) of
MAIN-UNIT.
Does the same symptom
appear even if R858 (2.7k) is
removed and the power is
supplied again ? NO Check IC704, D728, D762 and D736. If there are no
problems, check the resistance value between pins (1)
and (6) of P704.
When the value is low (several
Ω
- several hundred
Ω
),
disconnect P704. If the value is still low, the parts of 24V
line are defective.
When the resistance value is several k
Ω
check the
inverter unit.
YES
Check Q724, D731 , D734,
IC707, D751 , D753, D754,
D741 , D759 and D746.