Hello one and all,
My first post here so please accept my apologies if I make any mistakes, I am somewhat new to the LCD repair scene but was hoping someone could lend some advice - I have read every other thread regarding this board to no avail and even the standard guides.
I recently bought a faulty Samsung 2253BW LCD monitor in the hopes of re-capping and fixing but after replacing the bulged capacitors still no joy:
While i have been writing this post one of the STM8309's failed during probing (Burn mark on top of it now) so i will give the symptoms before and after the failure:
Having tested / replaced where needed all of the electrolytic capacitors with my DMM (AMPROBE AM-220) that should no longer be the issue. When the power is pressed I got a feint buzz from the power board (not sure which component) and the standard blue LED blinking on / off.
The voltages for the 12 pin plug are as follows:
Pin No - Legend value – LED ON voltage (LED OFF Voltage / Comments)
1. B-DIM – 4.76V (0V)
2. 13.0V – 14.6 (Fluctuates from 14 – 14.8V, then LED turns off and cycles again)
3. GND
4. GND
5. 5.1V – 5.31V (4.44V)
6. 5.1V – “
7. A-DIM – 4.45V (0V)
8. On/Off 0V (1.59V – Jumps on cycle)
9. 3.3V – 3.3V (1.5V)
10. LED – 2.86V (0V)
11. Key 1 – 1.8v
12. Key 2 – 0v
The buzzing noise was not a constant tone and would cycle - After the STM8309 failed the LED is now solid, the buzzing is still there but no longer cycles:
Solid LED – Burned STM8309 chip.
Now:
1. B-DIM – 0.1v
2. 13.0V – 16.6v
3. GND
4. GND
5. 5.1V – 5.28v
6. 5.1V – 5.28v
7. A-DIM – 0.63v
8. On/Off – 2.61v
9. 3.3V – 3.3v
10. LED – 2.85v
11. Key 1 – 1.83v
12. Key 2 –1.83v
I have also tested:
2x Fuses, 2x 3 pin transistors, Backlit inverters, Diodes and checked for short circuits / cold joints - All seem ok.
As i say, i am not sure if it was the STM8309 that was failing which caused the original problem and if replacing that will help or not?
When testing the components i get the following readings (Using the Diode setting on the DMM):
Burned STM8309 (U202)
1 - 7/8: 0.49V
2 - 7/8: 0.93V
3 - 5/6: 0.16v
4 - 5/6: 0.16v
Non-Burned STM8309 (U203)
1 - 7/8: .366V
2 - 7/8: .846V
3 - 5/6: 0.023v
4 - 5/6: 0.717v
All of those readings are taken in-situ with Positive on pins 1 - 4 and negative on pins 5 - 8.
If there is anything else you need me to check i will be more than happy to.
Warm regards,
Demon
My first post here so please accept my apologies if I make any mistakes, I am somewhat new to the LCD repair scene but was hoping someone could lend some advice - I have read every other thread regarding this board to no avail and even the standard guides.
I recently bought a faulty Samsung 2253BW LCD monitor in the hopes of re-capping and fixing but after replacing the bulged capacitors still no joy:
While i have been writing this post one of the STM8309's failed during probing (Burn mark on top of it now) so i will give the symptoms before and after the failure:
Having tested / replaced where needed all of the electrolytic capacitors with my DMM (AMPROBE AM-220) that should no longer be the issue. When the power is pressed I got a feint buzz from the power board (not sure which component) and the standard blue LED blinking on / off.
The voltages for the 12 pin plug are as follows:
Pin No - Legend value – LED ON voltage (LED OFF Voltage / Comments)
1. B-DIM – 4.76V (0V)
2. 13.0V – 14.6 (Fluctuates from 14 – 14.8V, then LED turns off and cycles again)
3. GND
4. GND
5. 5.1V – 5.31V (4.44V)
6. 5.1V – “
7. A-DIM – 4.45V (0V)
8. On/Off 0V (1.59V – Jumps on cycle)
9. 3.3V – 3.3V (1.5V)
10. LED – 2.86V (0V)
11. Key 1 – 1.8v
12. Key 2 – 0v
The buzzing noise was not a constant tone and would cycle - After the STM8309 failed the LED is now solid, the buzzing is still there but no longer cycles:
Solid LED – Burned STM8309 chip.
Now:
1. B-DIM – 0.1v
2. 13.0V – 16.6v
3. GND
4. GND
5. 5.1V – 5.28v
6. 5.1V – 5.28v
7. A-DIM – 0.63v
8. On/Off – 2.61v
9. 3.3V – 3.3v
10. LED – 2.85v
11. Key 1 – 1.83v
12. Key 2 –1.83v
I have also tested:
2x Fuses, 2x 3 pin transistors, Backlit inverters, Diodes and checked for short circuits / cold joints - All seem ok.
As i say, i am not sure if it was the STM8309 that was failing which caused the original problem and if replacing that will help or not?
When testing the components i get the following readings (Using the Diode setting on the DMM):
Burned STM8309 (U202)
1 - 7/8: 0.49V
2 - 7/8: 0.93V
3 - 5/6: 0.16v
4 - 5/6: 0.16v
Non-Burned STM8309 (U203)
1 - 7/8: .366V
2 - 7/8: .846V
3 - 5/6: 0.023v
4 - 5/6: 0.717v
All of those readings are taken in-situ with Positive on pins 1 - 4 and negative on pins 5 - 8.
If there is anything else you need me to check i will be more than happy to.
Warm regards,
Demon
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