UA55H8000 - bad capacitor on panel (SOLVED)
Owned a Samsung UA55H8000 (curved) LCD.
Picture disappeared, sound still there.
Took it apart, and measured the backlight LEDs:
8 sets altogether: 4 measured 90V each, 4 measured 30V each. Seems OK.
Watched the T-CON, and saw only 2 of 3 LEDs light up.
Ordered a replacement on eBay (not 1:1, but close enough).
Arrived, same 2 LEDs on, 1 off.
Unlikely to have same bad T-CON, right?
On the T-CON measured 12V (input) and 1.2V, 2.5V and 3.3V around - all OK.
But no other Gamma voltages...
Then, when measuring the DC-DC diodes, realized that DD02 had a ground short on both sides. Odd.
And with the panel flat cables off - the short went away!
Turns out that QD01 is a 6-pin MOSFET, SW controlled, switching the 12V into the panel (and to the Gamma DC-DC convertor chip). DD02 is connected to it's output.
The culprit was the panel - showed a 1 Ohm resistance to ground on it's 12V supply input (fed by QD01)
Disconnected it from the T-CON, and connected a 5 Amp supply, only to watch bubbles under a 0.1uF bypass capacitor (see picture!) on next to one of the chips...
Cap removed, old T-CON working, TV back to life.
Happy days
Picture disappeared, sound still there.
Took it apart, and measured the backlight LEDs:
8 sets altogether: 4 measured 90V each, 4 measured 30V each. Seems OK.
Watched the T-CON, and saw only 2 of 3 LEDs light up.
Ordered a replacement on eBay (not 1:1, but close enough).
Arrived, same 2 LEDs on, 1 off.
Unlikely to have same bad T-CON, right?
On the T-CON measured 12V (input) and 1.2V, 2.5V and 3.3V around - all OK.
But no other Gamma voltages...
Then, when measuring the DC-DC diodes, realized that DD02 had a ground short on both sides. Odd.
And with the panel flat cables off - the short went away!
Turns out that QD01 is a 6-pin MOSFET, SW controlled, switching the 12V into the panel (and to the Gamma DC-DC convertor chip). DD02 is connected to it's output.
The culprit was the panel - showed a 1 Ohm resistance to ground on it's 12V supply input (fed by QD01)
Disconnected it from the T-CON, and connected a 5 Amp supply, only to watch bubbles under a 0.1uF bypass capacitor (see picture!) on next to one of the chips...
Cap removed, old T-CON working, TV back to life.
Happy days
Attached Files
