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Aric
Aric, Technician
Category: TV
Satisfied Customers: 33198
Experience:  10+ yrs. experience installing and repairing TVs and A/V systems. Owner of A/V installation and repair business.
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Hello, I have a Samsung LCD TV model #LN40A530P1F that intermittently

Resolved Question:

Hello,
I have a Samsung LCD TV model #LN40A530P1F that intermittently looses its picture but still has sound. The problem began a couple months ago & seemed to occur when there was a sudden change to the picture (such as a change to picture source, using some of the interactive cable features). The problem could be corrected by resetting/removing power to TV and trying again. It has now gotten worse & will just loose picture for no apparent reason.

Thanks,
Matt
Submitted: 8 months ago.
Category: TV
Expert:  Aric replied 8 months ago.
Hello, My name is XXXXX XXXXX I will be glad to assist you. Please keep in mind that there may be a few minutes between replies, as I research your problem.

How long have you had the set for and when did the problem occur?
Additionally, what is connected to the TV for devices (DVD, cable box, etc.), and do you have the same issue regardless of which Device you're watching?
If you press MENU on the TV when the problem is occurring, does the MENU display normally on the full screen?
Customer: replied 8 months ago.


I've had the TV for about 5 yrs. The problem started 2 months ago. There is a Blueray player/home theater & a cable box connected. Yes, I have the same issues regardless of what I am watching.


No, there is no menu display.

Expert:  Aric replied 8 months ago.
Okay thank you. So just to make sure I understand correctly, this problem will happen whether you're watching a Blu ray disc, or also from the Cable Box correct?

Also, when the screen goes black, pressing MENU on the Samsung, or specifically the Samsung remote will not produce anything at all on the screen.

When the screen goes black, is it still backlit- meaning slightly lighter than when the set is off?

How often does it go black, and are you at the set right now, and do you have a flashlight handy?
Customer: replied 8 months ago.


Yes, that is correct & there is nothing on the screen when pressing the menu on the Samsung remote.


 


When the set goes black it is not still backlight. Its completely black as if it were off.


 


It started going black everyonce in awhile now its almost every time I go to watch it. Sometimes if I leave it unplugged for a little while it will work but will eventually go black again for no reason.


 


I do have a flashlight handy.

Expert:  Aric replied 8 months ago.
Thank you. When the screen goes black, please shine a flashlight almost directly against the screen, at a 45 degree angle, then look very very closely. Do you see a dim, shadowy image behind the screen?
Customer: replied 8 months ago.


yes, there is a dim image behind the screen.

Expert:  Aric replied 8 months ago.
Okay, this indicates that your Backlight Inverters are shutting down, and it's either due to a faulty Inverter, or the Power Supply board's output to the Inverter is causing the problem. Are you looking to repair yourself? If so, then you'll need a meter capable of measuring DC voltages, and to see if it's the power supply output that's failing, or the Inverter that is. If you're not comfortable with this type of repair, then you're looking at between $200-$250 parts and labor for this type of repair.

If you need further assistance or a link to parts, let me know and I will continue to assist you.


Customer: replied 8 months ago.

 


Looking to repair myself. Do'nt have a multimeter hany right now but will tomorrow. Can you talk me through checking the power supply or inverter?

Expert:  Aric replied 8 months ago.

The first thing you would want to check for in the set, are the capacitors visually, making sure none are bulged, swollen or leaking fluid. The Power Supply is the board inside the TV that power cord directly attaches to.

Any that do not appear cylindrical, or are leaking you would take the rating (In uf), and the voltage off the cap (example: 2200 uf, 50 vdc), and cross reference them at the sites below:

http://www.digikey.com/




http://www.mouser.com/




They each solder into place with two leads, a positive and a negative. Make sure you solder the news ones in the same way, or they will explode when the TV is powered up.

Make sure you are careful not to un-solder any other adjacent circuit traces when removing the old caps, and carefully solder in the new ones allowing the solder to flow into the joint. Replace any and ALL caps that are questionable. Remember- when in doubt, change them out.


Try powering up the TV, and if the set operates normally, then you have solved the issue by replacing the faulty cap(s).


If it does not, then you would need to isolate which board is causing the problem by measuring the Power Supply Voltages.


Please only proceed if you have experience measuring live voltages on a circuit board level.

Use a DVM (Digital Volt Meter) set to DC volts, put the Black probe of the Meter on an RCA jack shield on the back of the TV, then use the Red probe and probe all of the Outputs for voltage (correct voltages will be stamped on the power supply at the outputs). Do this with NOTHING connected to the Power supply but AC power, the Mainboard, and the little board that houses the Power Switch. If a voltage is missing/ fluctuating, then the power board needs to be replaced.

If the power supply outputs its rated voltages, then connect the other boards one at a time until one causes it to shut down. This board would have the short causing the supply to SOS, and would need to be replaced.

A good source to locate replacement boards is http://www.shopjimmy.com/


and http://www.discountmerchant.com/


 


If you need further assistance, let me know.


If this answers your question, please rate the answer accordingly, as it is the only way we Experts get paid for our knowledge on the site. Tips and Bonuses are welcome and appreciated!!

Aric, Technician
Category: TV
Satisfied Customers: 33198
Experience: 10+ yrs. experience installing and repairing TVs and A/V systems. Owner of A/V installation and repair business.
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