Samsung BN44-00807E Low Backlight

[Warrensmith]

Symptom is dim backlight - this set came in with almost no backlight.

Samsung UN55JU6500FX2A

1 - Replaced all backlight LED strips (set had lots of hours at level 20 backlight)
2 - Changed out what appeared to be a bad Q9102C on BN44-00807E - not shorted or burned but appeared to be open. I was able to read (with difficulty) the part number - however I may have misread it - Can someone confirm that this is indeed an AOD9N40.

Backlight improved significantly - about like it would be set to a level 3 or 4. Setting all the way to 20 seems to not increase brightness.

If I unplug main board backlight does go to 100% - full brightness.

Backlight voltage to strips - about 75v
Voltage prior to the Q9102C ( measured on any of the 3 3.3uf caps ) 300V

So we have plenty of voltage prior to Q9102C. Q9102C appears to be functioning since when disconnecting main board in goes to full conduction

Did I replace Q9102C with the correct part number - AOD9N40

Thanks in advance for assistance

[nomoresonys]

Re: Samsung BN44-00807E Low Backlight

go into setting and see if eco sensor or something is turned on, I usually turn all that crap off, too distracting.

[Warrensmith]

Re: Samsung BN44-00807E Low Backlight

Update:
Found that is brightness was turned up past 80, the backlight increased to proper levels.

BUT THEN...
Q9102C began smoking and burned.

Replaced q9102C again, retested and lights come on but chip is getting way too hot.

Checked backlight strips with the 'backlight tester from jimmy and they are working fine ( all strings light) . No shorts measured to ground.

I want to measure the current to the lights but need to acquire a clamp on DC tester. an AOD9N40 is good for 9amps continuous.
I am wondering if the current sense in the board has gone bad.

[nomoresonys]

Re: Samsung BN44-00807E Low Backlight

Can you post a picture of that area?

[nomoresonys]

Re: Samsung BN44-00807E Low Backlight

did you get the replacement from a reliable source?

[Warrensmith]

Re: Samsung BN44-00807E Low Backlight

Image of board area and the AOD9n40 in package.

[lotas]

Re: Samsung BN44-00807E Low Backlight

The photo looks like a fake, the original as in this photo.

[nomoresonys]

Re: Samsung BN44-00807E Low Backlight

wondering if it was a d3n40 that went in there?? looks pretty funky might want to take it off clean up that area, can use isopropyl alcohol and a toothbrush, maybe clean up that solder above thats connecting those squares too, maybe check condition of ZD9103, ZD9104, D9103, R9109, R9110.

[Warrensmith]

Re: Samsung BN44-00807E Low Backlight

SOLVED - well the culprit are bad AOD9n40 devices as replacement - yuup ebay. As you suggested probably counterfeit devices from china.

Fortunately I has an original MOD9n40 that I has carefully pulled from another board and installed it into the BN44-00807E that had smoked multiple AOD9n40 devices.

MOD9n40 running cool event with mainboard pulled and pushing full brightness on the LED backlight.

Going to run the new backlights at 12-13 - no higher.

Have on vertical black line on the screen - have reseated all ribbon cables and checked for breaks - can't solve this but its possible the screen had this symptom prior to disassembly. This was a set running in a short term beach rental property so probably has lots of hours.

Its now going to be installed in my workshop - so no need for it to be perfect.

Thanks for those who suggested solutions.

Warren

[nomoresonys]

Re: Samsung BN44-00807E Low Backlight

nice job ok then looks like a damn counterfeit, very nice catch Lotus. maybe you can share the seller so everyone can avoid them. i would report them to ebay, hard to tell if it would do any good, ebay probably dont care as long as they're making money from them.