Samsung LE40A676 dark picture

[PowerAmpFreak]

Hello all.
A Samsung LE40A676 has a very dark picture. It seems the backlight does not operate to its full potential.
It's possible to adjust the backlight intensity between 0 and 10 in the menu, but it's way too dark.
Where should I start?
PSU/Inverterboard or the current transformer board?

[capkid]

Re: Samsung LE40A676 dark picture

First, check PSU output voltages.

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

If you mean the +5V and +12V, they're good.
I can't tell if the HV output of the inverter has proper level.

[budm]

Re: Samsung LE40A676 dark picture

Did you try Mute 182 power (tv is off)
(On some models, Factory Reset is on this menu, on some, you must go into the “Options” submenu.

https://www.badcaps.net/forum/showthread.php?t=24809
I had this same problem and it is corrected by using the factory reset.

[budm]

Re: Samsung LE40A676 dark picture

By the way, the I reset is UN40C7000, so I am not sure if MUTE 182 Power will work with the LE series or not. The UN 40C when I put on DEMO mode, it looks great, but in normal operation, the brightness was really low even when the brightness and Backlights set all the way up.
You can try this one also:
press : Info,
Menu,
Mute,
Power

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Thanks - will try!

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

On this one, there is no "factory reset" or reset option in service menu.

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Maybe I have to replace the main eeprom on mainboard to rewrite the factory data?

[tom66]

Re: Samsung LE40A676 dark picture

http://wiki.samygo.tv/index.php5/UnB...y_EEPROM_Reset

Factory reset on these I thought was hidden in one of the sub menu.

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Do you mean perhaps in the user available menu?

[tom66]

Re: Samsung LE40A676 dark picture

No, factory menu... I'm sure I used it before on the A656...

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Yep, I was inside the factory menu. There are a limited number of functions there.
None of them opens a reset as far as I can see, the screen is so dark so I must sit very close to the TV to see anything at all.
I don't know if this is normal but the checksum is displayed as "0000" , correct?

It's possible to see the backlight flickers, may it be a inverter failure after all?

[tom66]

Re: Samsung LE40A676 dark picture

Through the back of the set does the backlight flicker? Yes inverter failure is possible. Have you played with BACKLIGHT setting in user menu?

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

The BACKLIGHT setting in user menu does change the backlight intensity like it should, except for it's waaaay too dark all of the time.
This set has the high voltage inverter combined in the PSU. Then the HV is fed to a separate board with a lot of small transformers on it.

[tom66]

Re: Samsung LE40A676 dark picture

Check BRI or DIM signal from main board?

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Check BRI or DIM signal from main board?

Will do, but what is most likely being bad. The PSU/inverter board OR the transformer board? Could one faulty transformer affect the entire screen being dark?

[budm]

Re: Samsung LE40A676 dark picture

I just reset another 46" UN series today with low volume and very dark pictures, this one the FACTORY reset is on the second page of the service menu.

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

The screen is so dark .. can't hardly see what I'm doing.
Do anyone of you have an LE series to check the service menu for me ?
And where the reset is to be found.
I can enter the service menu in the normal way, and it's possible to enter "options" and "calibration", but not the "advanced" sub menu. Don't know why..

[tom66]

Re: Samsung LE40A676 dark picture

Will do, but what is most likely being bad. The PSU/inverter board OR the transformer board? Could one faulty transformer affect the entire screen being dark?

If the BRI is low, mainboard. You could disconnect BRI temporarily, force it higher to 5V using 1k resistor, so you can see service menu then locate reset option. If BRI is good, say around 2V and rises with backlight setting in user menu, it will be the IP board or balance board, likely IP board. (IP board is inverter/PSU combo.)

[PowerAmpFreak]

Re: Samsung LE40A676 dark picture

Great advice. Will check this tomorrow!