Insignia NS-39L700A12 backlight transformer high pitched wine

[MikeRWK]

The tv won't turn on most of the time. It will try for a few seconds and quit, there's a lower buzzing then if it fires the transformer whines. All the caps look good visually there aren't any bulged caps or indications of leakage.

When I press on the transformer in question the whine changes.

Here's a video of it https://streamable.com/gatxa4

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

There look like there are at least 2 bad caps, C556 & C554, (or it is just the angle of the picture) start by replacing them. One is for the standby +5 the other is for the +12v. see if that helps.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

There look like there are at least 2 bad caps, C556 & C554, (or it is just the angle of the picture) start by replacing them. One is for the standby +5 the other is for the +12v. see if that helps.

It's just the picture but heating the big cap made it turn on, now to find a replacement.

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

It's just the picture but heating the big cap made it turn on, now to find a replacement.

Which "big cap" are you referring to?

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

The big cap is 560uf, if I parallel 2 270uf capacitors will it be happy with 540uf? I attached a pic to my previous post.

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Are you sure heating C517 changed the operation or were you heating one of the smaller caps like C519 C520
You should be able to try the two 270µf and see if it makes a difference

[petehall347]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

grounding screws are missing

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

grounding screws are missing

It's screwed down now and there's no difference.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

I tested this pnp transistor and it seems to be dead, could that cause my problem? It was pretty close to the big capacitor where I heated the board with a hairdryer.

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Is this V503???? Explain "dead", shorted, open, leaky ? If it is this transistor it is the vcc switch for the main and pfc ic's
Slow turn on is likely due to bad caps, C536 & C531, standby startup cap. & vcc supply cap.
C519 & C520 are vcc & start cap for the main ic N504

Have you checked the voltage across the main filter C517? check it in standby and then again when the tv is turned on. this voltage should be 160vdc in standby and go up to around (200vdc?) when tv is on.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Standby is 162-163 and when I try and power it up it goes up to 206 and settles at 199 while hissing. Then it goes crazy and the voltage fluctuates https://streamable.com/wjr9s6 I was pressing the volume buttons in the video.

Also is this resistor supposed to be hot to the touch?

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Is this V503???? Explain "dead", shorted, open, leaky ? If it is this transistor it is the vcc switch for the main and pfc ic's
Slow turn on is likely due to bad caps, C536 & C531, standby startup cap. & vcc supply cap.
C519 & C520 are vcc & start cap for the main ic N504

Have you checked the voltage across the main filter C517? check it in standby and then again when the tv is turned on. this voltage should be 160vdc in standby and go up to around (200vdc?) when tv is on.

By dead I meant open, I tested it according to this video https://youtu.be/GFitoQSbLvA?t=302 , while I don't understand the language I see what he's doing.

[dick_barton]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

There look like there are at least 2 bad caps, C556 & C554, (or it is just the angle of the picture) start by replacing them. One is for the standby +5 the other is for the +12v. see if that helps.

As R_J says, some of those capacitors do look as though the tops are doming. Are you certain they are not??

[nomoresonys]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Agree, either there's some doming or it's one hellofa optical illusion.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

They don't look to be doming but I'll swap them out.

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

By dead I meant open, I tested it according to this video https://youtu.be/GFitoQSbLvA?t=302 , while I don't understand the language I see what he's doing.

If the transistor, which I am guessing is V503 was open, the tv would not operate at all. It is best to check the emitter and collector voltage when the tv is turned ON, Using HOT GROUND. this will give tell you if you have proper vcc voltage for the primary ic's to operate.
The main filter voltage going from 160vdc to 200vdc indicates the pfc circuit is working. I would replace those small electrolytics in the primary circuits, they can go weak and cause this type of problem.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

If the transistor, which I am guessing is V503 was open, the tv would not operate at all. It is best to check the emitter and collector voltage when the tv is turned ON, Using HOT GROUND. this will give tell you if you have proper vcc voltage for the primary ic's to operate.
The main filter voltage going from 160vdc to 200vdc indicates the pfc circuit is working. I would replace those small electrolytics in the primary circuits, they can go weak and cause this type of problem.

I checked the voltages on the transistor the pic with the meter illuminated is Emitter and the other pic is Collector voltage. I replaced all the capacitors besides 4 that I don't have at the moment and it seems more likely to power up when its first plugged in but its still the same.

It's occurred to me I'm going to need a capacitance meter to make things easier in the future.

[nomoresonys]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

I checked the voltages on the transistor the pic with the meter illuminated is Emitter and the other pic is Collector voltage. I replaced all the capacitors besides 4 that I don't have at the moment and it seems more likely to power up when its first plugged in but its still the same.

It's occurred to me I'm going to need a capacitance meter to make things easier in the future.

Ebay is loaded with them, about 7-15 bucks, on a slow boat from china, can get a closer shipper but it's about double the price.

[MikeRWK]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

Ebay is loaded with them, about 7-15 bucks, on a slow boat from china, can get a closer shipper but it's about double the price.

I usually pull them from working tvs with broken screens, which is why I really need to buy a capacitance meter.

[R_J]

Re: Insignia NS-39L700A12 backlight transformer high pitched wine

I checked the voltages on the transistor the pic with the meter illuminated is Emitter and the other pic is Collector voltage. I replaced all the capacitors besides 4 that I don't have at the moment and it seems more likely to power up when its first plugged in but its still the same.

It's occurred to me I'm going to need a capacitance meter to make things easier in the future.

I asked for the emitter & collector voltages to see if the ic's had the proper vcc, Since you did'nt post it here, I suggest you look up the ic's datasheet and see if they are correct.