Sanyo DP50741 Service Manual page 2

SANYO: DP50740-00 / 02 / 03 & DP50710-00 / 01 & DP50741-01
with PANASONIC 50" PLASMA PANEL (MD50H13NBE)
SYMPTOM: TV's GREEN POWER LED WILL NOT REMAIN ON
Unplugging any power cable from the SMPS to isolate the defective PCB will not work on this Panasonic panel.
note:
Unplugging any of the power cables will cause the SMPS to shut down.
a) Unplug LVDS Cable (40 pin connector) from Main to Digital "D" Bd. (D5 connector) behind Main:
This will eliminate the Main Bd., and see if the SMPS will power ON automatically, and remain ON.
Plug the AC Cord to power (do not push the Pwr Key on the TV) and see if the SMPS will power ON.
If the SMPS powers ON and remains ON, then the Main Bd. should be tried. If the SMPS continues to shutdown
then resistance checks (#1-#12) below should be done.
note: This panel has a self test mode, and unplugging the LVDS starts the self test. No raster is displayed,
because a special jig is needed to activate the raster & video.
RESISTANCE CHECKS TO POSSIBLY ISOLATE DEFECTIVE PCB
1) Is pin #1 or #2 (55-60V) of (P35 connector) shorted to chassis Gnd?
yes, shorted = PDP Panel N/G
not shorted = go to step #2
2) Is Pin #5 (5V) of (P25 connector) shorted to chassis Gnd?
yes, shorted = go to step #3
not shorted = go to step #4
3) Disconnect (p25 connector)
Is Pin #5 (5V) of (P25 connector) shorted to chassis Gnd?
yes, shorted = SMPS N/G
not shorted = go to step #4
4) Disconnect (SC20 connector)
Is pin #30 (5V) of SC20 connector shorted to chassis Gnd?
yes, shorted = SC Bd N/G
not shorted = go to step #5
5) Disconnect (SS23 connector)
Is pin #1 (5V) of SS23 connector shorted to chassis Gnd?
yes, shorted = SS Bd N/G
not shorted = go to step #6
Reconnect P25, SC20, & SS23 Connectors
6) Disconnect (SC2 connector)
Is TPVSUS (SC2, pin #1, 193V) on SC Bd. Shorted to chassis Gnd?
yes, shorted = SC Bd. N/G
not shorted = go to step #7
7) Reconnect SC2 and disconnect (SS11 connector)
Is TPVSUS (SS11, pin #1, 193V) on SS Bd. Shorted to chassis Gnd?
yes, shorted = SS Bd. N/G
not shorted = Power ON TV, and check TPVSUS on SC Bd. for 193V before shutdown
If no output, = SMPS N/G
If 193V OK is before shutdown, SC Bd. may be defective (can not be sure)
Reconnect SS11 Connector
8) Is TPSC1 (143V) shorted to base pattern of SU/SD Bd?
Base Pattern Test Points are on attached page (please do not use chassis Gnd)
yes, shorted = go to step #9
not shorted = go to step #11, not necessary to check #9 - #10
9) Disconnect SU41 connector
Is TPSC1 shorted to base pattern of SU/SD Bd?
not shorted = SU Bd. may be defective
yes, shorted = go to step #10
10) Reconnect SU41 and disconnect SD42 connector
Is TPSC1 shorted to base pattern of SU/SD Bd?
not shorted = SD Bd. may be defective
yes, shorted = SC Bd. may be defective
11)
Measure resistance across C956 (143V across cap.) on SD Bd.. If resistance is only a few ohms, the SD BD. is defective.
12)
Measure resistance across C907 (143V across cap.) on SU Bd.. If resistance is only a few ohms, the SU BD. is defective.
If you can not find anything wrong and you suspect the panel is shorted, you can unplug the eight flat ribbons from the panel
to the buffer bds. (SU & SD) and see if the SMPS will remain ON. You can not unplug the flat ribbons to the Sustain Drive
(SS) Bd. (if you unplug the flat ribbon/s to the SS Bd. the panel will shut down). If all PCBs and other connections are OK, the
SMPS will power ON and have all voltages with these ribbons unplugged. If the SMPS should remain ON with the ribbons
unplugged, you should re-connect them and then verify that the SMPS still shuts down when they are connected.
note: The SMPS will remain ON, if one or more of the flat ribbons are unplugged from the panel to the buffer bds. (SU & SD),
if the PCBs and other connections are OK.
12/28/10
2010-9B
Location of connectors is
on page #2
Please re-install all PCB mounting
screws whenever a board is
changed, and before re-testing
the TV. The ground screws are
needed to prevent damage to the
PCB.
After working on TV, if it has
several horizontal lines or bars,
please try reseating the flat
ribbons going to the SU & SD Bds.
p#1