SONY KDL-32NL140 no power light

[zogthegreat]

Hi everyone!

I'm a long time lurker on the forum, but this is my first post. A friend gave me a SONY KDL-32NL140 LCD TV that will not power up. The power light does not come on when it is plugged in and it does not turn on when you push the power button.

I was thinking it might be bad caps, (this has usually been the problem when I have similar problems wit computer LCD's), but the capacitors seem fine, with no bulges or leaks. I tested the ceramic fuse next to the power in and I'm getting 38.2v AC, (red arrow in the picture). Not sure if this is normal or not, (that's why I'm posting here!).



I checked the back of this and the other 2 boards and I don't see any signs that they are burnt or have anything bad on them.





Any suggestions?

Thanks

zog

[freakaftr8]

Re: SONY KDL-32NL140 no power light

What are you getting in DC voltage across that big filter cap? Also I'm not sure about how you're testing that fuse but with the TV unplugged doing ohms test on the main fuse and see if its open or not first.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

Hi freakaftr8,

What are you getting in DC voltage across that big filter cap?

I get .025 DCV on the large round capacitor/filter

Also I'm not sure about how you're testing that fuse

I was measuring it with the TV plugged in. (Not the correct way, I assume? )

with the TV unplugged doing ohms test on the main fuse and see if its open or not first.

I get 00.8 ohms, I get the same when I cross the leads on my cheap Chinese multimeter. When I test on a 3' piece of solid core copper wire, I get 2.0 oms, (to give you a reference range).

[freakaftr8]

Re: SONY KDL-32NL140 no power light

Ok fuse is good there is however no power on the primary side for some reason.

[freakaftr8]

Re: SONY KDL-32NL140 no power light

Aha! Can you focus in on those 3 blue mylar capacitors to the left of the fuse? Is that bottom one blown to pieces?

[Gootch46]

Re: SONY KDL-32NL140 no power light

Great catch there freakaftr8 it sure looks like it to me also.

[budm]

Re: SONY KDL-32NL140 no power light

Pictures of the bottom side of the power suppl board?
Those 3 blue X/Y caps looks like they are glued down with black silicone.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

Pictures of the bottom side of the power suppl board?
Those 3 blue X/Y caps looks like they are glued down with black silicone.

LOL, I was just about to post that up!

I scraped off as as much of the silicon that I could. The capacitors look OK. I don't have an ESR tester, so I will try to get the parts to build a capacitance tester and start testing them.

Question, do I need to unmount the caps in order to test them or can I test them while they are still on the board?

[budm]

Re: SONY KDL-32NL140 no power light

I doubt that they are bad. I need the pictures of the bottom side of the board to see how the AC gets to the rectifier.
SJ does not have the picture of the bottom side:
http://www.shopjimmy.com/sony-1-474-...wer-supply.htm

[zogthegreat]

Re: SONY KDL-32NL140 no power light

Hi budm,

Here you go. I'm sorry about the image quality, my camera just died with a "lens error"! (I guess I'm taking something else apart today!)



I labeled the 120v, large cap and 3 small caps to give you some reference points. If you need more, let me know.

Thanks!

[budm]

Re: SONY KDL-32NL140 no power light

the bridge rectifier is on the top right of the picture. Do you get 120VAC between the two inner legs for the bridge?
Please make it better focus.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

I get 116.5 across the 2 inner pins of the bridge rectifier.

Is this better? Or should | go borrow a camera? (I'm using my phone until I have time to try fixing my camera).

[budm]

Re: SONY KDL-32NL140 no power light

I get 116.5 across the 2 inner pins of the bridge rectifier.

Is this better? Or should | go borrow a camera? (I'm using my phone until I have time to try fixing my camera).

Then you should see DCV between the two outer pins.
Thanks for the much better picture.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

I'm not getting anything DCV on the two outer pins. This my bad part?

SJ does not have the picture of the bottom side:
http://www.shopjimmy.com/sony-1-474-...wer-supply.htm

Can I upload a copy of the pic there? It might help someone else in the future.

[budm]

Re: SONY KDL-32NL140 no power light

Meter set to DCV, right?
Otherwise check the bridge.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

Meter set to DCV, right?
Otherwise check the bridge.

When I have it set to DCV, I get L.0, but when I hit the "range" button, I get 160.0mv

I'm using a Vici VC86 multimeter:



(Sorry, my son has a degree in electronics, but I'm not as good as he is for this type of stuff [or as knowledgeable]. But you give me an engine to take apart..... )

[budm]

Re: SONY KDL-32NL140 no power light

Take the meter and check your car battery to see what it shows.

[zogthegreat]

Re: SONY KDL-32NL140 no power light

I get 12.66v off my car battery.

[budm]

Re: SONY KDL-32NL140 no power light

Just curious, put the meter in AC and measure between the two out side pins again.
BTW, did you check the bridge in diode mode to see what it shows?

[zogthegreat]

Re: SONY KDL-32NL140 no power light

OK, this is what I got:

Diode mode:

Pin 1 = Black
Pin 2 =
Pin 3 =
Pin 4 = Red

reading = .478

Pin 1 = Red
Pin 2 =
Pin 3 =
Pin 4 = Black

reading = 0.L

Pin 1 =
Pin 2 = Black or Red
Pin 3 = Red or Black
Pin 4 =

reading = 0.l

ACV:

Pin 1 = Black
Pin 2 =
Pin 3 =
Pin 4 = Red

reading = 0.58

Pin 1 =
Pin 2 = Black or Red
Pin 3 = Red or Black
Pin 4 =

reading = 0.L