Samsung LNT4053H BL ISSUR

[jkb242]

I do not have a schematic for this set but would like to get one.

I have sound and a faint picture if room is very dark and flashlight is pointed at screen. Power on is good no caps appear to be stressed bulged or leaking.

On power up there is a brief flash of faint BL then dark screen.

I cannot find any fuses to check except main power fuses and of course they are fine. I believe the BL lamps are CCFL TYPE. Need to test inverter or seeking advice on isolating BL fault.

Much thanks

[dick_barton]

Re: Samsung LNT4053H BL ISSUR

Can you post sharp clear pictures of your boards and the interconnections which will help. Add them as attachments.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Indeed please standby and thanks for replying!!

[jkb242]

Re: Samsung LNT4053H BL ISSUR

please advise if pictures need to be labeled.

Thanks

[ReeceyBurger123]

Re: Samsung LNT4053H BL ISSUR

Remove the psu and get us images of the bottom side please, common issue with these supplies is cold solder joints on the inverter side of things.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Indeed I will and thank yo for your input. Will clean and reflow and examine under microscope I use for iPhone logic board repair. Don't have scope camera but can get close enough with magnifying lamp to get some informative pictures.

Thanks again!!

[jkb242]

Re: Samsung LNT4053H BL ISSUR

I will get the picture of the board, but I did remove and examine it. It appears that perhaps silver bearning solder was used in manufacturing. Took longer than normal at 480c to get to reflow even with flux. I did not find any suspicious cold or poor solder connections but reflowed the caps in the inverter part of the power board. That did not produce any change in the BL issue. When I powered it up I noticed the BL came on for about 1 second then immediately off again. I believe this was what it was doing originally but because I was looking at the Rea of the screen in a dark room. The BL was easily noticed for the brief moment it was on. I remember seeing the same thing from the front of the screen but it was much easier to see this from the rear.

It's beginning to appear to me that something is breaking down or flashing over which kills the BL rail. Again have sound and power cycle on is normal with exception of BL.

Thanks, and I welcome any additional input.

[budm]

Re: Samsung LNT4053H BL ISSUR

What is the P/N of that power supply/invreter board? BN44-?????

[jkb242]

Re: Samsung LNT4053H BL ISSUR

The power/inverter board number is BN4400167.

Thanks very much for your reply and additional information to follow.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Will be posting pictures of the solder side of this board this AM.

Thanks

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Power/inverter board detail:

Note that I have reflowed some of the solder connections that looked suspicious to me. Reflowing at 480c was quite slow making me think that solder on board is silver bearing.

Looking forward to your continued support and feedback

Thanks

[budm]

Re: Samsung LNT4053H BL ISSUR

The power/inverter board number is BN4400167.

Thanks very much for your reply and additional information to follow.

Which version? A, B, C, or D?
http://www.shopjimmy.com/catalogsear.../?q=BN44-00167

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Thanks for the power board schematic that's great.

I discovered missing 13vdc at pin 19 on the 24 pin connector to the system board but noted from your schematic it's merely jumper to pin 20 and 21 so if it's on the other two pins which it is its a non issue.

Can I use an 12 watt black light CCFL tube to test the BL output instead of the standard screw in CCFL you modified to access the pins.

Thanks I'll keep you posted.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Noticed on the schematic that shows the inverter feed that there is a 16 pin DIP shown below the two switching transistors connected to the 385vdc coil feed. I do not have this cup on my board do assuming it was part of the rev1.1.

All voltages check out so now will confirm if the transistors are switching. I don't see how they could be since there is only one other winding that connects to the BL's.

Thanks again for the help thus far!

[jkb242]

Re: Samsung LNT4053H BL ISSUR

TESTING HIGH VOLTAGE CONNECTING A LOW WATTAGE CCFL TEST BULB

This method is described and introduced by Budm and offers a handy way to test the BL drive from the power supply board.

My test lamp has two leads on each end of the helix shaped lamp. I am looking for clarification as to the proper connection the two pairs of lead for the BL test. The test lamp Budm used seems to only one lead coming from each end of the heliax test lamp.

Thanks picture attached.

[budm]

Re: Samsung LNT4053H BL ISSUR

I just twisted those two wires that come out from the lamp's end together, that is why it looks like one wire.
So which revision of the board you have? If it is not A or B then the diagram may not match what you have on the board.
You may not be able to use this lamp for testing, the power supply/inverter board high Voltage output is fed into the Balancer board.
There is a small connector from the Balancer board to the Power supply/Inverter board, you need to take the DCV readings on the 12V pin and the LD pin.
We know we have high Voltage because the backlights did flash on for seconds, but the circuit may have gone into protection shutdown.

[jkb242]

Re: Samsung LNT4053H BL ISSUR

Need additional help please.

Was attempting to measure switching of q1801 at the gate and being very careful but in probing the gate hears the relay de-energize. Now have loss of standby from system board. I need the the schematic for t
System to find where std by originates.

Please help, thanks very much.

[vinceroger69]

Re: Samsung LNT4053H BL ISSUR

just looked at picture 2 the A version box on the pcb board printing is ticked so should be the A version he has if the op cant find the details.

[budm]

Re: Samsung LNT4053H BL ISSUR

OK, I see the board number on the barcode sticker now.

[vinceroger69]

Re: Samsung LNT4053H BL ISSUR

I just noticed you had asked for the version number a couple of times, its hard to help someone without the proper details.