Samsung HPT4254 , No Power, Repaired

Attention, see note at bottom of this post.

This is a repost from my Blog, this seems to be a popular one so I thought it would be good to put here on the forum.

C&P

Had a service call today for a Samsung HPT4254 Plasma TV. Customer said he went to bed with the TV on and when he woke up the TV was ticking, tick, tick, tick..etc. No response when the power button was pushed and he had to unplug it to turn it off. When I arrived I plugged the TV in and it still had the symptom. After opening the TV , I removed the PSU(Power Supply Unit) and discharged the large filter capacitors in the primary side of the PSU and then checked the board for bad/cold solder connections, and checked the ESR of all the electrolytic capacitors on the board, and checked the fuses. All capacitors tested good, found very bad ring cracks on MOSFETs QX801 & QX802 and re soldered these connections. Found fuse F803 was open, at first it seemed OK, when checking continuity it gave me a continuous beep, but it was distorted and low and there was a resistance that was too large measured on the indicator for a fuse. After removing the fuse and testing out of circuit, it was actually open and measuring across the fuse terminals the resistance was still there, so I checked the corresponding circuit including MOSFETS Q5801 & Q5802, both MOSFETs were shorted, one between gate and drain and one between gate and both drain and source and shorted from drain to source. After replacing Both shorted MOSFETs and F803(8A 250V Time Delay Fuse) the TV fired up and worked like new. Hope this helps some of you that have the same failure with this model TV. Both MOSFETs were 13N50CF.



Attention go to the original post at my blog to see updates on this repair:Here is a link to the original post at the Preher-Tech Blog.Click Here

Thank you for posting this I am sure that it will come in handy for me in the future