Samsung PN51D550C1F - No Power ON

[sly1990]

1st time TV goes out after 16 month of purchase.
Turned off the TV and never came back ON until I fixed it once.
I found some IC shorted on the X-Main. (When I was unplugging the X, TV went ON.)

So, I replaced all Power of the IC from a same batch of 30J124 instead of 30G124 (Rated 200V higher), RJP30H and SF10A400

TV Worked great for 3 months but when I wasnt home, my wife told me that she heard a 2 sec hissing sound followed by a loud "POP" or "POW" coming from TV then it shutted down.

I fixed the X-Main again but this time it is not powering ON even when unplugging X-Main.
I looked for exploded, cracked, shorted IC or bad CAP and semiconductors on other boards, none were found.
TV wont turn on. Clicks once and Only Green led slowly flashing.


So, I ordered a PSU, a Y and a X Main board.

The led still blinks slowly but still not powering ON. (same symptoms if I reinstall the old PCBs I fixed)
All voltages VA and VS are good for less than a second then drop down to 0V.

I found that if I unplug the ribbon cable going from logic board to Y-Main, Voltages are Ok on Y-Main and Tv Turn ON. (No Image obviously)
Or, if I Unplug the Y-Main power connector from PSU, TV turns ON (Y-Buffer installed or not) and the VA & VS are also as they should on the PSU, 207V and 58V,
But, If both are connected, Only the slow blinking of the Green LED happens.

Before ordering any other PCBs (Buffer or Logic), I would like to know if there is any way to know if the logic board could be the culprit?

Any Idea?

Thanks!

[tw2005]

Re: Samsung PN51D550C1F - No Power ON

Sounds like the logic is doing it's job and detecting a fault. replacement boards can always be faulty.

Maybe check out the y buffers for short since they're the only thing not touched.