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The LN46A530 has a 46" display, combined with SRS TruSurround XT. The PC input allows this display to double as a 46" computer monitor

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My Samsung LN46C550J1F TV won't turn on and has no red light, help?

My TV is a Samsung LN46C550J1F. After a power surge and also a move in the same 24 hour span, it stopped turning on. There is no red light. I’ve tried all the power sources and other power cables as well, so ruled those out. I’ve removed the back and looked visually at the fuse and it does not appear to have any damage, whether blown or bulged. Please help further!

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Hi,

Do you have a DMM (digital multimeter) and know how to use it?

It will be necessary to test the fuses (there are two) with an Ohmmeter to make sure that they’re OK. Do this with the power disconnected from the TV.

If they are then next you will have to perform “live” testing to check if the 5V Standby power signal is being sent to the mainboard from the power board on the 5V_Det. lead. (pin 2 on the cable connector to the mainboard)

Be safety aware as there is exposed lethal AC voltage on the power board when performing live testing. If you don’t know how to test safely when this voltage is present, then don’t do it! Call a reputable, professional TV repair service and ask for a quote.

If there is no 5V standby voltage then there is a problem with the power board.

If there is 5V standby voltage, then check that it is appearing at the ,mainboard at the connector at the end of the cable between the two boards. If it is there also then you have a mainboard problem. It is the mainboard that turns on the Standby power light when the power is connected to the TV.

If you don’t have a DMM then try the following:

Disconnect the power from the Tv and then disconnect the mainboard cable from the power board. make sure that the other power board cables are connected.

Reconnect the power to the TV.

The screen backlight should turn on and stay on. There will be no picture because the mainboard is disconnected.

If they turn on this proves that the power board is mostly OK (not total proof though) and that is may be a mainboard problem. If they don’t turn on it is a power board problem

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Jayeff, I tested the fuses and they're both fine. I wasn't entirely sure how to test the standby voltage at the mainboard as I couldn't get the lead into the connector. However, I did disconnect the mainboard from the power board and the backlight did turn on and stay on. Seems it's likely to be a mainboard problem. What do I do next?

@Ross Sacharow

Check that the standby voltage and all the other voltages as shown on the power board are there at the power board connector to the mainboard, with the cable disconnected to the mainboard. The power board is turned fullon when the cable is disconnected so they all should be there.

Since you can't get into the connector on the mainboard, check that the Standby voltage is getting to the end of the cable from the power board to the mainboard at the mainboard end, just to prove the cable is OK. Alternatively disconnect the power from the TV and use an Ohmmeter to make sure that it is OK - safer as it doesn't matter if you slip with the meter test leads ;-)

mainboard schematics are very hard to find online if they are there at all.

It may be best to source a replacement mainboard from a supplier who accepts returns for a minimal cost to you if it is not the problem.

Search for the mainboard's "Board number' (printed on the mainboard) to get suppliers as sometimes searching for the "make and model number of the TV mainboard" may result in the wrong mainboard for the location of the TV as it may have different firmware loaded into the eeprom on the mainboard and won't work.

If you find a board then verify that it is OK for your TV model number

Thanks for the help Jayeff. I did confirm all the voltages are working at the power board connector. Wasn't quite sure how to check the standby voltage at the end of the cable, but either way seems that a new mainboard is needed. Can't seem to find my BN96-14769A main board (or other suitable replacements) in stock anywhere, so may have to wait or call it a lost cause.

@Ross Sacharow

The way to prove the cable is to either disconnect it from both boards and then use an Ohmmeter and check each wire from end to end for continuity or note which pin the Standby voltage leaves the power board on and it will arrive at the mainboard on the same pin number if it is a flat ribbon cable. If they're individual wires making up a harness cable then note the colour of the Standby voltage wire where it leaves the power board and then find the same colour wire at the mainboard connector and test the voltage on the pin that it is connected to.

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