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Repair guides and support for your Samsung TV.

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How to make sure Samsung UN55H6203A isn’t overdriving new LEDs

Hello- I just replaced the led strips in my Samsung UN55H6203 which were burnt/blown/bad. I’m afraid the power board may be over driving the LEDs but I’m not sure how exactly to tell. Can anyone help?

I saw some power board repair kits on eBay but would prefer to diagnose the issue myself rather than swap components without knowing what’s bad. I know replacing the resistors is somewhat common in other Samsung’s but would like to be be thorough and understand what resistance would be appropriate.

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Hi @chillin014

Looking at the power board, the voltage to the LEDs should be 268V @ 380mA.

If the voltage and current is correct then this is all that you can go on.

If it is not this value, then you would need the power board schematic (I couldn’t find one online) to find out why or manually measure or test every component in the relevant section of the power board, out of circuit i.e. disconnect one leg from the board, to make sure that it is the value as marked.

Electronics engineers have designed the board and selected the correct component values to suit. This of course doesn’t mean that some components may have drifted in their set values over time thereby affecting the output.

Were the repair kits you found for your specific power board model (including Revision number)? If it was for your board then go with it. Repair kits were generally only issued when a problem became noticeable due to the high number of failures of the TV or the board.

If you’re not sure whether it is OK or not you could always try adjusting the backlight setting down from maximum (if it is there) so that they’re not operating at full current and check if the picture is still acceptable to you. Go to Menu > Picture > Picture Mode (Choose a picture mode e.g. Dynamic, Standard, Natural, Movie) > Backlight

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Thanks a lot Jayeff! Sorry for the slow response. I will see if I can figure out how to measure the output. It seems with the LED harness plugged in there is no voltage but then when plugged in and I place my probe on the harness the LEDs shut off suddenly. (like some kind of safety feature).

The repair kit I saw was a one-off on eBay but it popped up when I searched the board number. This made me think there might be a somewhat common issue. Also I was thinking to another (edge-lit) Samsung I repaired which also over-drove the LEDs and caused a similar issue. On that model the repair kit was available as it was a common issue.

Just trying to play it safe since the old LEDs were so blown out on nearly every strip.

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@chillin014

I find it very strange that connecting a Voltmeter between a +ve LED supply lead (is it CNL802 on the power board?) and an earth point (screwhead on board) would shut down the LEDs. Unless you managed to accidentally short out 2 pins when measuring ;-)

A DMM voltmeter's usually minimum 20KΩ/V resistance value shouldn't drop the load that much to make it shut off, but then again I don't know what safeguards are built into the SMPS.

If using the 1000V DC scale on the meter that would place 20MΩ across the load which would draw minimal current i.e. µA which shouldn't affect the output I wouldn't have thought. After all that's what Voltmeters are designed to do, measure the voltage at different points in a circuit and not disrupt the circuit operation too much if at all.

I realize that it would be difficult to measure the current flowing through each strip as you would have to contrive somehow to place the DMM's Ammeter in series with one leg of each feed.

If you can measure the voltage on a particular +ve LED supply lead at the power board and you know how many LEDs are on the strip(s?) being fed by that one lead (check each +ve LED supply lead) then you can work out the voltage drop across each LED to see if it is too high i.e. divide the voltage by the number of LEDs. Normally for a single, standard white LED it's around 3.3V but it may be different for backlight LEDs I don't know.

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Christopher Hill crwdns2934231:0crwdne2934231:0
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