Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

[beedoola]

I have a 32'' Samsung. The power supply voltages test fine and when I connect the PS board to the Backlight inverted and plug give it all power, the backlight comes on.

When I hook up the main board back up with the PS and Inverter, I get nothing.

Blinking red light on the front panel.

Is the Main board just toast, or is there anything I can do to troubleshoot it?

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

anyone?

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

You can do some real good visual inspection and check some voltage readings on the voltage regulator IC and that's about it.
Did you try heating and cooling of the main board yet?

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

You can do some real good visual inspection and check some voltage readings on the voltage regulator IC and that's about it.
Did you try heating and cooling of the main board yet?

Heating it how?

Notice how the large heatseek is titled slightly? I'm wondering if that chip heated up too much.

I have a heat gun.

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

Can someone tell me the Pinout of this connector on the main board?

When the power board is connected, something from the main board shorts all power - measure the voltage on the PS board and I get nothing (with the MBoard connected), unplug the main board and the voltage on the PS board reads 24v, as it should.

I need to know the Pinout for the main board so I can see if I can track down the short.

[tom66]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

The pin out is just right of it.
Please upload photos to this site or to IMGUR as I cannot view full image on photobucket.

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

The pin out is just right of it.
Please upload photos to this site or to IMGUR as I cannot view full image on photobucket.

Yes, I see the legend on the PCB, but there aren't any numbers near the pins to say which is Pin 1, etc.

I'm not sure if they go: 1, 2
3, 4

or

1
2
3
4

etc.

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

"When the power board is connected, something from the main board shorts all power - measure the voltage on the PS board and I get nothing (with the MBoard connected), unplug the main board and the voltage on the PS board reads 24v, as it should." That is because the main board is forcing the PS_ON to go low and not allow the power supply to turn on.
I use hair dryer to heat up the board.

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

"When the power board is connected, something from the main board shorts all power - measure the voltage on the PS board and I get nothing (with the MBoard connected), unplug the main board and the voltage on the PS board reads 24v, as it should." That is because the main board is forcing the PS_ON to go low and not allow the power supply to turn on.
I use hair dryer to heat up the board.

Should I heat up the board by itself or plugged in to the PS board?

Do I heat up the whole board or sections?

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

boards are all connected, no power to the TV then use hair dryer (heat gun will be to hot and may melt the plastic) to heat up the whole main board for 2~3 minutes then apply the power to see if it will come on.

[steves7839]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

The legend follows the pinout. You can confirm this by checking the connector socket. Pin 1 is usually marked with a triangle or circle molded into the connector, and with silkscreen on the component side of the board.

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

See the picture attached.

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

I heated up the board and that did not get it to power.

Pin 2 - Switch Power and Pin 16 - SW Inverter both are shorted to ground when the PS is hooked up.

When measuring the Main board without the PS connected, or anything else, those pins to do read as shorted to ground.

[myfastgti]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

I had Samsung with similar problem and it turned out to be SDRAM was defective.

First heat the SDRAM with heatsink (Big red circle)chip for 30sec and see if the TV turns on if not check the 4 pin mosfet besides the RAM, sometimes it short.

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

I heated up the board and that did not get it to power.

Pin 2 - Switch Power and Pin 16 - SW Inverter both are shorted to ground when the PS is hooked up.

When measuring the Main board without the PS connected, or anything else, those pins to do read as shorted to ground.

Do the resistance show as <1 Ohm? No Tv is not plugged in, right?

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

I had Samsung with similar problem and it turned out to be SDRAM was defective.

First heat the SDRAM with heatsink (Big red circle)chip for 30sec and see if the TV turns on if not check the 4 pin mosfet besides the RAM, sometimes it short.

Tried that and nothing happened, no shorts, as far as I can tell.

Do the resistance show as <1 Ohm? No Tv is not plugged in, right?

plugged in, Pin 2 is 54R, Pin 16 is 25R

unplugged they drop in resistance, after powering pin 2 is around 10M and drops, Pin 16 was less and drops over time.

[budm]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

Quote:
Originally Posted by budm View Post
Do the resistance show as <1 Ohm? No Tv is not plugged in, right?
plugged in, Pin 2 is 54R, Pin 16 is 25R

unplugged they drop in resistance, after powering pin 2 is around 10M and drops, Pin 16 was less and drops over time."

When you do the resistance testing, DO NOT have power applied to the unit, you can also damage the meter if the unit has power.

[Ltank]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

Sometimes when Main Board Silkscreen does not show pinout. Simply go to P.S. connection to main board. P.S. is labeled and trace it to the main board wire by wire. A royal pain but you can see what is supposed to be on that pin

[beedoola]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

I had Samsung with similar problem and it turned out to be SDRAM was defective.

First heat the SDRAM with heatsink (Big red circle)chip for 30sec and see if the TV turns on if not check the 4 pin mosfet besides the RAM, sometimes it short.

4 Pin Mosfet or the 8 Pin IC you have circled?

I tested the pins on that IC and I can't tell if they're supposed to be but pins 5 and 6 are connected. I can't tell on the PCB if they're supposed to be.

pin 7 and 8 are also connected (i.e. show continuity test on my DMM) but I can clearly see they share trace.

[myfastgti]

Re: Samsung LN32C540F2DXZA: Won't turn on, PS and Inverter OK

Yes its a 8 pin dual n-channel mosfet from Alpha and omega number AO4800BL or AO4801. There should be 12 v or 11.8 v at pins 5,6,7 and 8 when the power button is pressed. If not check if you have any voltage at pin 2 and 4.

Usually these fet's don't fail but so far I've only seen one failure