RCA rlded3950a-b sound but no video

[MrBowtie]

I have a RCA 39 inch led hdtv that made a serious pop noise and picture went black but sound was ok. Thankfully I came across your forums and read for a couple of days now and decided to try and fix it myself. After the pop and video going i unplugged the tv right away. I plugged it back in and tv came on normally but only lasted about 15 minutes and video went black but still had sound. If I turn it off and back on right away it wound not change but if I wait just a minute or two it would come on normal again but only last five minutes and gone again. It doesn't matter if you unplug it and plug in again does it change anything. It seems like you have to wait about 10 or 15 minutes to get it to work 15 minutes at most no matter how long i wait plugged in or not. I also noticed when the video goes black...I can still see video if i use a flashlight near the screen. So needless to say the tv is 12 days over its 1 year warranty "lesson learned lol" and no help from RCA except to ship it to them and they will fix it for $175.00 + shipping and handling. So I took the cover off the back after finding and reading your forums and found a blue ceramic cap blown at C22 on the board. the cap is a 221 1kv. I replaced the cap and tried the tv but the tv does the same thing. So i took the back off again and noticed the voltage regulator " I think it is" I'm a newbie at this lol it's black and has three legs and is screwed to a heat sink. It looks like two legs shorted when the cap blew. Could this cause the problem and how would i go about checking it with a meter? Sorry for the long post.

[vinceroger69]

Re: RCA rlded3950a-b sound but no video

can you post some good clear pictures so we can see the part you are describing what is the part number of the part concerned.

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

Here are some pics

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

I'm not to sure of the part number....can't quite see the whole number. I'll take another look and see it i can take another pic.

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

Not sure how to circle things in pics but here's a couple of more. In first two pics i posted the ceramic cap i replaced is just above the yellow transformer and to the right. The voltage regulator beside the cap to the right looks like the two legs closest to the cap shorted. Can i check this somehow?

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

Being a newbie i think i made a mistake calling it a transistor instead of a voltage regulator. Edited and fixed.

[vinceroger69]

Re: RCA rlded3950a-b sound but no video

whats the psu part number printed on the board? my internet is having issues loading pictures tonight we can see if we can get a schematic then for it and see what the part number is.

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

PL390101b 6021010157-a. I looked up PL390101b and it says it's a Apex power supply.

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

The only other number i see on the board is LEKE LKP-PLO65

[vinceroger69]

Re: RCA rlded3950a-b sound but no video

yes have been looking for a schematic i cant find one do you think you can remove the part you think is faulty as post a good picture of it as its very hard to see it from your pictures yoy can also test it whilst it out of circuit.

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

It's a P7NK89ZFP G40M6 CHN 225N. Here are some more pics. How do i test it? Thanks for helping vinceroger69.

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

p7nk80zfp not 89 i would order 1 and replace it. plus it looks like it got hot according to the marks on the board

[tom66]

Re: RCA rlded3950a-b sound but no video

I would also replace the controller chip for that MOSFET, do you have a picture of the underside of the board near that transistor? When the MOSFET fails, it can also damage the controller chip.

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

set dmm to 20k ohms and put black on pin 2 and touch red to pin 1 then to pin 3 it should rise when it goes to pin 3 everyone has different ways to check them you can google how to check a n-channel mosfet and if you use your fingers to touch pin 1 and 2 at the same time it will "reset" it and you can test it again

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

Oops your right 80. Yeah it looks like it shorted but I'm not sure if it happened because the ceramic cap blew beside it or if the transistor shorted and caused the cap to blow.

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

i would also check d5 it looks like it might of got hot also. to check put dmm in diode mode and check red on 1 leg black on other leg then switch them around and give us the readings should read ol 1 way and give a reading the other way

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

i would guess the mosfet went bad causing the cap to blow but i am not as good as diagnosing these things like tom is

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

i retrack what i said probably the cap blew causing the mosfet to go bad but either way i think that is gonna need to be replaced plus pics of the bottom of the board so tom can check it out

[MrBowtie]

Re: RCA rlded3950a-b sound but no video

Here's a pic of bottom where i removed transistor.

[philliesfan30m]

Re: RCA rlded3950a-b sound but no video

that chip looks to be ok but looks can be deceiving. did you check d5?