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Repair Tips
Below some failure symptoms are given, followedby a repair tip.
zSet is dead and makes hiccuping sound
"Main Power Supply" is available. Hiccupping stops when L5561is
zSet 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!
zSet 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.
zSet is in
Set is in
zSet 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.
zSet 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
7/8/2004
