Sharp LC-50LE771E Service Manual ▷ View online
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C. Staying in Stand-by Mode
Problem: Staying in stand-by mode, no other operation
This problem indicates a short on Vcc voltages. Protect pin should be logic high while normal
operation. When there is a short circuit protect pin will be logic low. If you detect logic low
on protect pin, unplug the TV set and control voltage points with a multimeter to find the
shorted voltage to ground.
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D. IR Problem
Problem: LED or IR not working
Check LED card supply on MB90 chasis.
3. Staying in Stand by Mode
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D. IR Problem
Problem: LED or IR not working
Check LED card supply on MB90 chasis.
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E. Keypad Touchpad Problems
Problem: Keypad or Touchpad is not working
Check keypad supply on MB90.
4. IR Problem
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F. USB Problems
Problem: USB is not working or no USB Detection.
Check USB Supply, It should be nearly 5V. Also USB Enable should be logic high.
G. No Sound Problem
Problem: No audio at main TV speaker outputs.
Check supply voltages of 24V VDD_AUDIO, 3.3V AUDIO_AVDD and AUDIO_DVDD
with a voltage-meter. There may be a problem in headphone connector or headphone detect
circuit (when headphone is connected, speakers are automatically muted). Measure voltage at
HP_DETECT pin, it should be 3.3v.
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E. Keypad Touchpad Problems
Problem: Keypad or Touchpad is not working
Check keypad supply on MB90.
5. Keypad Touchpad Problems
6. USB Problems
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F. USB Problems
Problem: USB is not working or no USB Detection.
Check USB Supply, It should be nearly 5V. Also USB Enable should be logic high.
G. No Sound Problem
Problem: No audio at main TV speaker outputs.
Check supply voltages of 24V VDD_AUDIO, 3.3V AUDIO_AVDD and AUDIO_DVDD
with a voltage-meter. There may be a problem in headphone connector or headphone detect
circuit (when headphone is connected, speakers are automatically muted). Measure voltage at
HP_DETECT pin, it should be 3.3v.
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H. Standby On/Off Problem
Problem: Device can not boot, TV hangs in standby mode.
There may be a problem about power supply. Check main supplies with a voltage-meter. Also
there may be a problem about SW. Try to update TV with latest SW. Additionally it is good
to check SW printouts via Teraterm. These printouts may give a clue about the problem. You
can use Scart-1 for terraterm connection.
I. No Signal Problem
Problem: No signal in TV mode.
Check tuner supply voltage; 5V_VCC, 3V3_TUNER and 1V8_TUNER. Check tuner options
are correctly set in Service menu. Check AGC voltage at IF_AGC pin of tuner.
7. No Sound problem
8. Standby On/Off Problem
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