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Repair Tips
Below some failure symptoms are given, followedby a repair tip.
z
Set is dead and makes hiccuping sound
"Main Power Supply" is available. Hiccupping stops when L5561is de-soldered, meaning
that problem is in the "Main Power Supply"line. No output voltages at LOT, no horizontal
deflection. Reason:line transistor 7460 is defective.
z
Set is dead,and makes no sound
Check power supply IC 7520. Result: voltage at pins 1,3, 4, 5 and 6 are about 180 V and
pin 8 is 0 V. The reason why thevoltage on these pins is so high is because the output
driver (pin6) has an open load. That is why MOSFET 7521 is not able to switch.Reason:
feedback resistor 3523 is defective. Caution : Be careful measuringthe gate of 7521;
circuitry is very high ohmic and can easily bedamaged!
z
Set is in hiccupmode and shuts down after 8 seconds Blinking LED (setis in SDAM
mode) indicates error 5. As it is unlikely that P "POR"and "+8V protection" happen at the
same time, measure the"+8V" supply. If this voltage is missing, check transistor7480.
z
Set is in non-stophiccup mode
Set is in over-current mode; check the secondary sensing (optocoupler 7515) and the
"Main Power Supply" voltage. Signal "Stdby_con"must be logic low under normal
operation conditions and goes tohigh (3.3 V) under standby and fault conditions.
z
Set turns on,but without picture and sound
The screen shows snow, but OSD and other menus are okay.Blinking LED procedure
indicates error 11, so problem is expectedin the tuner (part reference number 1000).
Check presence of supplyvoltages. "Vlotaux+5V" voltages at pin 5 and 7 are
okay;"VT_supply" at pin 9 is missing. Conclusion: resistor 3460is defective.
z
Set turns on,but with a half screen at the bottom. Sound is okay
Blinking LED (set is in SDAM mode) indicates error 3. Check"Vlotaux+11V" and "+50V".
If they are okay, problemis expected in the vertical amplifier IC 7471. Use an
oscilloscopeto measure the waveform on pin 17 of the UOC. Also measure the
waveformat pin 1 of IC 7471. If the signal there is missing, a defectiveresistor R3244
caused the problem
Pa
g
e 16 of 16SPMS
7/8/2004