Samsung LN55A950D1FXZA Black Screen

[Optix]

Ok, I been reading for a week now. I am a little stump with my TV. First the symptoms.

Woke up one day and had some lines on the top of the TV, sound was working. The input button on the TV was blinking non stop. Menu is not viewable.

So I open TV, checked for the usual suspects "caps" power supply. I found a bad cap, replaced the cap but it did not solve my problem. After further reading I decided to replace the TCon board. Replaced the board, the lines on top disappeared, but the picture is still black, menu still not available.

So I am listening to tv and I can hear a little noise from the Back-light Inverter board. So I purchased a new Back-light inverter board and a new power supply, to rule out problems with other caps. No-GO still the same problem.

So I this point there are only two other boards to replace, the Samsung BN94-02103B Main Board or the Samsung BN94-02131A Dimming Board. I do not mind replacing them, but aside from not wanting to waste more money, the main board seems to be out of stock in many places. So my question is, could the Dimming board be the problem or should I keep on looking and replace the Main board?


Thanks for the help.

[selldoor]

Re: Samsung LN55A950D1FXZA Black Screen

Cant say I have heard of a dimming board, but dont do a lot with big tvs.
We could try and troubleshoot your mainboard with a view t repair if you have a multimeter and soldering equipment.

Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

I ordered the Dimming board, if that fails I will take pics tomorrow and post them in order to start troubleshooting.


Thanks for the warm welcome.

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

Well the Dim Board was a bust, Included are pictures of the front and back of the main Board. Please help me Diagnose the board.


Thanks

[selldoor]

Re: Samsung LN55A950D1FXZA Black Screen

Pics are not quite clear enough for trouble shooting - can you try and do them again
-try half a board side at a time. Looks like many regulators. Couple of things - back of the board top right- two components with 2 and half legs look burnt - are they? can you read the part numbers?
Front of the board the component with the Blued label has abrown spot on it - is it burnt?

[budm]

Re: Samsung LN55A950D1FXZA Black Screen

This tv uses LED backlights with one of those localize dimming of the screen so they can claim high contrast ratio.
From SAMSUNG website "1,000,000:1 dynamic contrast ratio with LED SmartLighting"
LOL.

[tom66]

Re: Samsung LN55A950D1FXZA Black Screen

My TV has infinity:1 ratio. Of course you have to turn it off to achieve that. Main board issues could be extensive and usually on Samsung it turns out to be a firmware problem!

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

They do not look burnt to my untrained eye, but how do I test them? Included are more pictures.



Thanks

[budm]

Re: Samsung LN55A950D1FXZA Black Screen

LOL, "infinity:1 ratio" that's a good one, they should put that in the advertisement.

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

Rear Pics.

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

Forgot Two Pics

[selldoor]

Re: Samsung LN55A950D1FXZA Black Screen

Hi - its getting late over here - will examine pics tomorrow - is that a reset switch I see and can you look again at Q105 - still looks burnt to me - can you clean it up with some isopropyl alcohol and see if you can read the part no with a magnifying glass

[Optix]

Re: Samsung LN55A950D1FXZA Black Screen

I cleaned it with alcohol and the part number i beleive is 19P06? Also has a number of T86B. How can I test to see if it is burned? The one corner looks a little funky, but not sure that it looks burnt.

[selldoor]

Re: Samsung LN55A950D1FXZA Black Screen

19P06 is a mosfet
Test as here
Mosfets

If you have a manual range multimeter, set it to 200 ohms (two hundred). This is for 3 pin ICs only. You can test a mosfet (Q, IC designation) "in circuit" by (power off and unplugged)

a) black on pin 1- red on pin 2 - record ohms
b) black on pin 1- red on pin 3 - record ohms
c) black on pin 2- red on pin 3 - record ohms

If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.

Note: a shorted mosfet would likely cause a very brief flash of the backlight or no backlight.
(From Retiredcaps guide)
https://www.badcaps.net/forum/showthread.php?t=10419