Troubleshooting a BN44-00440B power supply

[TheBigBen76]

Hi Folks,

I'm new here, name's Ben. Trying to fix a TV my neighbor threw out. Neighbor told me his TV repair guy "couldn't find the part". So I'm like "I got dis!"

to the project:

When plugged in the TV turns on, plays the power on tune, screen comes on, then it turns itself totally off. Assuming this is a power supply issue I removed the board from the TV and examine the boards various parts. No obvious blown components.

I have a UTL33T multi-meter that I've only used one other time. So anyone willing tell me how to test the board's components I'll follow the instructions.

TV is a LN40E550F7FXZA CH01. Power Supply is a BN44-00440B board.

I've got all the tools to diagnose the issue. Only tool I don't have for repair is a soldering tool, which I wouldn't be opposed to getting/learning to use.

Pic attached of board.

Thanks in advance!

[budm]

Re: Troubleshooting a BN44-00440B power supply

You need to Check the dc Voltage on the power supply board connector that goes to the main board, you need to check the Voltage when TV is OFF and when TV power switch is activated.
You MUST put down the pin names and follow by the Voltage reading for EACH pin (Pin names are printed on the board)

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

Little hazy.. But I'm proceeding this morning.

Plugged the board back up and going to let it shut itself off after the hitting the power switch then get readings.

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

So in the process of trying to test I fumbled the board, touching the TV, and creating a large spark.

Now the TV won't turn on at all. Replace whole board or did I blow one of those tiny fuses?

The fuse at 8025 is reading as no circuit now. I'm guessing a fuse should read as a circuit when tested.

[budm]

Re: Troubleshooting a BN44-00440B power supply

Good fuse should show the about the same resistance when you touch the two meter probes together.
Right now it can be just blown fuse or you may have damaged other component, I.E. bridge rectifier, MOSFET, etc., on the board so you need to test them, or just buy a new board.

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

Thinking it's just buy a new board now. Going to price them

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Try replacing the fuse then "carefully" test the board again if you got 2 seconds to black it may not be a powerboard issue.

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

Just seeing this. Already bought a board, will update next week when it arrives.

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

New Board came in, back to the same problem. After research it looks like the CM40t_chs "backlight inverter" is the issue.

This part seems to be very difficult to obtain, but not very expensive. Found a Mexican site that appears to have it, but not knowing Spanish I'm unsure. Haven't had time to look it back up from the desktop.

Any leads anyone knows of would be appreciated.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Shine a flashlight at the screen, try pushing menu on the tv or remote, see if you see any text or image at all.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Not sure why its not in english, went straight to electroparts warehouse don't appear to be there but its listed here. https://www.cafr.ebay.ca/itm/Samsung...-/171576904005

[TheBigBen76]

Re: Troubleshooting a BN44-00440B power supply

I'll try playing with the menus. Thanks for that link, I'm going to contact the seller to see if they still have it, the original sale is over.

[budm]

Re: Troubleshooting a BN44-00440B power supply

So now you have replacement power supply, you then you need to test the Voltages as I suggested in post 2 to find out if the main board is sending the control signals or not to the power supply board.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

I'll try playing with the menus. Thanks for that link, I'm going to contact the seller to see if they still have it, the original sale is over.

Already sold, bummer, couldnt tell without english.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Yes what bud said, check CN802 voltages, theres a little map/legend of expected voltages near by the connector, check them with all boards hooked up, tv in standby, make note, turn tv on and record any changes from standby, something like this: pin 12 A5v: standby 5 volts, power on 5 volts, check them all theres 2 rows, report all voltages.

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

This looks like your powersupply. https://www.shopjimmy.com/samsung-bn...upply-unit.htm

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Demonstration. https://www.youtube.com/watch?v=4v8DcqCNG4A

[nomoresonys]

Re: Troubleshooting a BN44-00440B power supply

Inverter board here, I would call to try to verify a match. https://atvpartselectronique.com/en/...ter-board.html