Troubleshooting Table - Sharp LC-26GA4D Service Manual

LC-26GA4D
LC-26GA4U
<Power supply>
No power supply (Front LED is off) or no power-up (Front LED does not change from red to green)
Is power cable properly connected to the main unit?
Is F701 normal?
Is BU+5V line (pin (16) of CN706, pin (8) of CN707 and pin
(4) of CN708) normal?
Are the wire harness, FFC, etc. in the set connected properly?
Is the voltage (approx. 380V) available at C709/C710 when the
power is turned on?
Is the voltage available in 15V line immediately after the power is
turned on?
Is each DC/DC converter output (IC707-711 and IC716) normal?
• Power switch: Top panel
(Main) Power (DC cutoff: Detected by microprocessor)
[Scheme of power supply system]
[(Main) Power OFF sequence]
1) (Main) Power OFF (DC switch)
2) (Main) Power shutoff is detected by the monitor microprocessor port.
3) Standby request (power cord) is sent to Seine from the microprocessor.
4) Seine shutdown process
5) Reception of shutdown permission from Seine
6) Monitor microcomputer turns off the relay to enter the standby mode.
TROUBLE SHOOTING TABLE
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
Seine
Relay
Main
Backup Monitor microprocessor
Connect the power cable properly, and turn on the power.
Replace F701, and turn on the power. If the fuse is still blown,
replace VA701, VA702, D701, D702, L703, Q701, Q702 and
IC701. Then repeat the check.
Is there any defective part or short-circuit in BU+5V line?
YES
Check the BU+5V line power circuits (F703,
D722, IC703, T703, PC702, D761, and IC715).
Remove the defective part or short-circuit, and repeat the check.
Reconnect the wire harness, FFC, etc. in the set properly, and
repeat the check.
Check the 380V line power circuits (L703, IC701, Q701-5, D706
and TH 701).
Check the 15V line power circuits (T701, T702, F704, Q706-14,
PC703-4, D708-17, IC702, L710, Q733-6, D735-6, D780 and
IC706).
Check each DC/DC converter and line (IC707-11 and IC716).
Replace if necessary.
(Main) Power
36
NO