Samsung UE48H6270SSXZG black screen after Smart TV logo

[Schule04]

Samsung UE48H6270SSXZG

Power supply is BN44-00709A
Mainboard is BN94-07385J

Got this TV from Ewaste.

Symptoms
The power LED comes on when plugged in. After pressing the power button the backlight lights up and stays lit. The Samsung Smart TV logo fades in and out. After that the display stays black and doesn't react to buttons on the TV or remote. TCON board has 3 blue LEDs which are lit. A small part of the backlight seems to flicker when the TV is powered up. TV shuts off after some minutes.

Attempted troubleshooting

- Disconnected TCON board

- Disconnected backlight from PSU

These didn't seem to make a difference.

My question is, shouldn't the TV power up if it was just a backlight issue and if it was disconnected? Or is this likely also mainboard/firmware issue?

I haven't done any measurements yet and to be honest am not sure which ones I should do.

[CapLeaker]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

I’d say you are on the right path with you firmware issue diagnosis. If you have a flash programmer, check the flash itself if it is still good.

Plug in the backlights to the power supply and disconnect the main board from the power supply, then plug it in to mains. With the main board disconnected, the power supply and the backlight should turn on as soon as you plug the power supply in. There should be no flickering etc. if something flickers, you are into changing backlights as well.

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

I do have an SPI programmer but nothing to read the main eMMC NAND.

I noticed that the full model name of the mainboard is BN41-02156A BN94-07385J. Do you think a BN94-07385 from a UE75H6470SS would work in this TV? Seems like it uses the same firmware but the panel is obviously not the same size.

The panel in my TV is a CY-GH048CSLV1H

[nomoresonys]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

If the connectors and input/outputs are the same I would try it, otherwise it could require some modifications, did one for myself not long ago, had to cut some of the back cover off because the board was sized differently, meaning the inputs didn't match up with the original board and the back cover input holes.

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

Replaced the mainboard with the one from a UE75H6470SS and it works, for the most part. The TV booted right up.

There's a faint blue/violet spot in the middle of the screen so some LEDs there are bad I guess?

The sound output seems to be broken, there is nothing coming out of the speakers. The headphone out on the mainboard works though. Seems like this board is a bit defective.

I changed the panel and TV type in the service menu to the correct model but nothing obvious changed.

[lotas]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

EDID fail, do your hdmi inputs work with this error?

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

Yeah they do work, tried them with a PS3 and a laptop. Is this related to the other issues? I read that apparently the EDID can be reprogrammed from the service menu, should I try that?

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

OK, fixed EDID with this guide: https://www.avsforum.com/threads/how...-work.1748778/

Nothing else seems to have changed though

[nomoresonys]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

wonder if it needs firmware update/pair.

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

Pairing what exactly? I doubt it, the speaker wires directly attach to the mainboard.

The speakers are marked as bn96-30334a

Here are some pics of the "new" mainboard

[Schule04]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

I think I figured out why there is no sound. The mainboard comes out of the 75" model and I realized they have a different power supply.

I compared both mainboards and there are some differences between the two. The 75" one has SMD components fitted near the power connector which are not present on the 48" one. All of these are marked with a _75 on the silkscreen which likely stands for 75" model.

The smaller PSU has those pins marked as not connected, they likely are connected on the 75" one. Maybe that model has bigger speakers and needs extra power or something, no idea.

In conclusion, these 75" mainboards are not suitable for the other size models.

[nomoresonys]

Re: Samsung UE48H6270SSXZG black screen after Smart TV logo

I was commenting on firmware update which is also called pairing or re-pairing but it could just be incompatible.