NS-50L440Na14 LCD Power supply issue

[pjpa]

Re: NS-50L440Na14 LCD Power supply issue

hi Bud, I don't have access to a camera until tomorrow AM. My problem on TV was it wouldn't turn on at all. I found that on PS board AY158P-4HF03 I had 120V AC at each side of fuse but no further. I measured an open on one side of LF3 and on the component next to it as well. It's designator is VNR1. When I removed LF3 the board was black underneath and the coil core also had black burned tape on it. I found a component that looked similar to LF3 on an old board on a broken TV my neighbor had. I had to attach some wires to get it to go into LF footprint on board because its bobbin is just slightly larger. When I did that I had 120V in several areas on hi side and 5V DC on +5Vsb. I then put a jumper between +5VSB and SB and all of the labeled DC voltages are present on all connectors. I will be able to put it back into the TV tomorrow evening. However, I'm concerned about VNR1 being opened. I don't know what it is or its purpose. This is my first attempt to repairing a TV. My niece asked me to look at it yesterday AM. I brought the board home with me but left the TV there. I have just been kind of blindly searching the internet for tips. Does anyone have any knowledge about what VNR1 may be it has numbers on it 105168K. Do you think the coil I put in on LF3 is ok to leave in there?

[budm]

Re: NS-50L440Na14 LCD Power supply issue

I cannot tell if that open component is until we can see the pictures and see how it is connected in the circuit.
I sounds like it is an NTC for inrush current limiter.

[pjpa]

Re: NS-50L440Na14 LCD Power supply issue

I was able to look at he component more closely under magnification this morning and realized that it actually said 10S681K and when I Googled that I found out it is a Metal Oxide Varistor. I will have to look closer at the board after work but I think it is connected across the main and I suppose it is for surge protection. I'm not 100% sure about that yet though.

[budm]

Re: NS-50L440Na14 LCD Power supply issue

That will be MOV which will be connected between Line and Neutral after the main fuse, it will blow if the Voltage exceed the rating so the TV may have been exposed to surge or over Voltage condition, the TV should work without MOV, it is for protection.
BTW, that is 10mm Dia. 420V MOV.

http://www.mouser.com/ProductDetail/...4umktO81LW0%3d

[pjpa]

Re: NS-50L440Na14 LCD Power supply issue

Thanks Bud I think MOV is actually ok. It is tough to read them with a meter. Do you know where I could get a replacement for LF3. The part I put in is kind of jury rigged

[budm]

Re: NS-50L440Na14 LCD Power supply issue

We still do not get to see the board yet.
It is not required for the power supply to operate, it is there to stop the noise from injecting back into the power line and also stop the noise from power line to inject into the power supply circuit.
If you are going to keep the TV for yourself then it will be OK to use what you have, but if you are going to sell the TV then you need to get the same part, may be from another broken TV.
Good MOV should show as open circuit using the meter in Ohm mode but to verify if it will still clamping the Voltage you will need high Voltage power supply with current limiter to test them.