Previous owner says this unit powers on and sometime has an image and sometimes not. They attempted to replace the main board but with no success.
TV came with the replacement mainboard as well as the original.
When the TV turns on there is no image or sound. No response to the remote or toggle button other than the power button. The power supply's relay was clipping here and there. It did that for several seconds even after I removed the mains. I did this even with no other boards connected (only the backlight was connected at the time). Backlight looks fine but I haven't tested it with a back light tester yet.
After I got my bearings with the TV I pulled the main board off to start testing for shorts. I actually started with the original mainboard and did the same check with the replacement board that was installed don the TV. I recently learned (thank you BadCap Vets) to check the coils for shorts on the rails so I proceeded to check ALL inductor coils (3R3, 1R0, 1R5, 1R0A, and 4R7). I also checked all ICs with 8 or less legs on them making note of anyone that had more than 1 leg that was shorted to ground. I marked the ground(s) pins in GREEN according to the pinout. The pins marked in RED are grounded but not labeled as ground.
I did this for both boards.
To my surprise the replacement board was also in bad shape but not as bad as the original board.
If you look at the picture of the original board you will see the coils which show shorted (red dot). You will also the ICs that I believe are defective or at least connected to the shorted component.
The replacement board reads grounded at the coils at L302, L303, L304 and the 1R0 coil right near the edge of the Heatsink. The adjacent IC12 is a Z3018IP and seems to be shorted to ground on pin 8. That coils reads shorted on the original as well but IC12 on that board seems good (not shorted on pin 8).
Bcos the coils on the replacement board did not show grounded in the lower left hand corner I took this to mean that the readings I got off the adjacent ICs were what they were supposed to be. Meaning the RED labeled PINs I marked on the Original board's ICs are not supposed to be grounded/shorted.
What should my first plan of attach be in tackling these shorts? Should I focus my efforts on the replacement as it 'appears' to have/has fewer number of issues?
I believe I should start by removing ICs to see if the short disappears from the nearby coils. And continue on that patch until all the shorts are eliminated.
I can then pull good ICs from the other board and replace them.
TV came with the replacement mainboard as well as the original.
When the TV turns on there is no image or sound. No response to the remote or toggle button other than the power button. The power supply's relay was clipping here and there. It did that for several seconds even after I removed the mains. I did this even with no other boards connected (only the backlight was connected at the time). Backlight looks fine but I haven't tested it with a back light tester yet.
After I got my bearings with the TV I pulled the main board off to start testing for shorts. I actually started with the original mainboard and did the same check with the replacement board that was installed don the TV. I recently learned (thank you BadCap Vets) to check the coils for shorts on the rails so I proceeded to check ALL inductor coils (3R3, 1R0, 1R5, 1R0A, and 4R7). I also checked all ICs with 8 or less legs on them making note of anyone that had more than 1 leg that was shorted to ground. I marked the ground(s) pins in GREEN according to the pinout. The pins marked in RED are grounded but not labeled as ground.
I did this for both boards.
To my surprise the replacement board was also in bad shape but not as bad as the original board.
If you look at the picture of the original board you will see the coils which show shorted (red dot). You will also the ICs that I believe are defective or at least connected to the shorted component.
The replacement board reads grounded at the coils at L302, L303, L304 and the 1R0 coil right near the edge of the Heatsink. The adjacent IC12 is a Z3018IP and seems to be shorted to ground on pin 8. That coils reads shorted on the original as well but IC12 on that board seems good (not shorted on pin 8).
Bcos the coils on the replacement board did not show grounded in the lower left hand corner I took this to mean that the readings I got off the adjacent ICs were what they were supposed to be. Meaning the RED labeled PINs I marked on the Original board's ICs are not supposed to be grounded/shorted.
What should my first plan of attach be in tackling these shorts? Should I focus my efforts on the replacement as it 'appears' to have/has fewer number of issues?
I believe I should start by removing ICs to see if the short disappears from the nearby coils. And continue on that patch until all the shorts are eliminated.
I can then pull good ICs from the other board and replace them.
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