Samsung LN52B630 No picture

[moegilla]

Hello all,
I have the above mentioned 52 inch LCD TV. It powers on , the screen flashes, then no picture. Audio is fine. No obviously blown caps on power or main board. Any ideas?
Thank you

[infringer]

Re: Samsung LN52B630 No picture

you have audio but no backlights do you have 24v at your power connections. The connectors should be connect tv to power with cover off laying on the floor do not touch anything else with your hands or anything metal. Stick the probes on the black on the ground and red on the +24 when tv is turned on see what voltage you have.

Be extremely careful not to touch anything not only could you create a lot more troubleshooting but you could end up in the hospital or dead if you do not exercise the proper precautions.

Wearing rubber gloves and electrical taping the probes so that only a 1/8th inch of the probe is exposed will surely help your odds of doing this safely.

[budm]

Re: Samsung LN52B630 No picture

This is power supply-backlights inverter board combination, so it does not use 24VDC for typical separate backlghts inverter setup. The inverter section runs on 400VDC power supply.
Since this power supply has PFC voltage booster circuits, please check the DC voltage on the two legs of the large DC filter cap (check on either one) 450VDC, when TV is plugged in but not turn on it should have about 165VDC on it, when the TV is turn on and the power board receives the PS_ON from the main board, the voltage on the cap should go up to about 400VDC.
Can you get closed up pictures of the connectors on the board so I can see the labels on them.
And as infringer indicated, be real careful since you will be working on the primary side.
What is the part number on this board?

[moegilla]

Re: Samsung LN52B630 No picture

tested the DC filter caps....got 164VDC plugged in not on, and 389VDC plugged in and powered..not sure what you meant by "connectors" so here are a few more pictures of the power board

[tom66]

Re: Samsung LN52B630 No picture

OK, the PFC is working, so that means the main board is also probably working (as it is sending the right power on signal.) In a dark room, can you see a dim glow from the screen? (Alternatively, on some TVs you can see a white glow from the holes in the back of the LCD panel.)

[budm]

Re: Samsung LN52B630 No picture

There are connectors with mutiple wires connect to them, ther are lable next to them that tell us what they are (right now they partial blocked). I am looking for BL_ON pin.
It looks like the pin23 is for INVERTER ON/OFF PIN, check the voltage on that pin.

[moegilla]

Re: Samsung LN52B630 No picture

how does one go about testing voltage on the pins? Ive attached closer looks at the connectors

[budm]

Re: Samsung LN52B630 No picture

It is the other connector on the top right of the picture in my post6, black probe on the chassis, and the read probe just poke into the socket of the connector, your probe will have to be skinny one.

[moegilla]

Re: Samsung LN52B630 No picture

which side is odd which even?

[budm]

Re: Samsung LN52B630 No picture

As you can see from the picture, there is label 1 for the top row (odd number) and 2 on the bottom row (even) in picture of post 6.
In picture in your post 7, then it will be the bottom row for odd, top row for even.

[moegilla]

Re: Samsung LN52B630 No picture

figured it out....5.08VDC

[budm]

Re: Samsung LN52B630 No picture

So pin 23 is 5V, if that is the case, the inverter transformer driver circuit is not working. I only expect about 3.3v or so.

[moegilla]

Re: Samsung LN52B630 No picture

any advice on the next step?

[moegilla]

Re: Samsung LN52B630 No picture

im gonna replace the four 1000uf caps see what goes down ill let cha know

[budm]

Re: Samsung LN52B630 No picture

By the way, is the fuse in the middle of the board OK? This fuse supply the power to the inverter circuit.

[moegilla]

Re: Samsung LN52B630 No picture

I turned the multimeter to 200 OHM, placed the leads on both sides and I get all sorts of readings , mostly staying from 1-10 but randomly jumps back and forth up to 180 ish and back down....doesnt stay consistent

[budm]

Re: Samsung LN52B630 No picture

It should read less than 1 Ohm. Board is not powered right?
Touch your two probes together, it should show less than one Ohm (test probe's resistance). Otherwise, remove the fuse and test it again.
The meter's batteries is OK?

[moegilla]

Re: Samsung LN52B630 No picture

So I replaced the 4 caps and replaced both ceramic fuses on the power board and still same issue...