Samsung Main Board - BN41-01800B

[sean0118]

Hi everyone,

I'm fixing a Samsung TV which was apparently damaged by lightening (along with a PS3 plugged into it). I don't have the tv here and I've forgotten the model number.

But anyway, the power supply board was shutting down due to over current protection. But runs fine with everything unplugged.

The main board (Echo P Unique BN41-01800B) has a short to ground on the output of the 1.8V regulator IC201 (UTC LD1117AG 18A01PDS6). Anyone have a schematic for this board?

I can't see any obvious damage, but there's a large shorted bypass capacitor next to some custom Samsung BGA called SDP1101. I *think* this may interface to the HDMI so may have been damaged through the PS3 which was plugged in.


So does anyone have a schematic for the BN41-01800B or a datasheet for the SDP1101? Or have any advice what to do next?

(attached images are not the actual board but same part number from shopjimmy)

[R_J]

Re: Samsung Main Board - BN41-01800B

Shopjimmy lists the models this board is used in,
UN46ES7500FXZA
UN46ES8000FXZA
UN55ES7500FXZA
UN55ES7550FXZA
UN55ES8000FXZA
UN60ES7500FXZA
UN60ES8000FXZA
UN65ES8000FXZA
UN75ES9000FXZA
I found a service manual but it does not have a schematic
The best I can suggest is use a bench power supply (1-1.5 v) or 1.5 volt battery and look for a component that gets hot.
You can put some ipa on the board and when you apply the voltage to the short, the ipa will evaporate really fast on the hot component, (only connect the voltage for a second or two, don't leave it connected)

[sean0118]

Re: Samsung Main Board - BN41-01800B

Shopjimmy lists the models this board is used in,
The best I can suggest is use a bench power supply (1-1.5 v) or 1.5 volt battery and look for a component that gets hot.
You can put some ipa on the board and when you apply the voltage to the short, the ipa will evaporate really fast on the hot component, (only connect the voltage for a second or two, don't leave it connected)

Seems like a decent idea, I'll give it a go.

[sean0118]

Re: Samsung Main Board - BN41-01800B

How much current would you expect to need?

My lab supply only goes up to 2A, nothing heats up at all.

[R_J]

Re: Samsung Main Board - BN41-01800B

2 amps should be lots, you said it the 1.8 volts is shorted to ground, Does the 1.5 volts from the supply drop to zero when you connect it to the 1.8 volt line? If there is a shorted cap, it will get very hot if it is shorted, the ic should also get hot if it is shorted.
It could be your supply is shuting down and not supplying any voltage, try an ordinary 1.5 volt battery

The LD1117AG can only supply about 800 miliamps, are you sure you have a short? , Does the input voltage to the regulator ic drop when the tv is turend on? If there was a short on the regulator's output, I would think the regulator ic would at least get hot but I can't see it shutting down the power supply.

[sean0118]

Re: Samsung Main Board - BN41-01800B

I thought 2A would be heaps too, but I left it on for ~ 1 minute and nothing heated up at all.

There's definitely a short somewhere on the rail. The lab supply goes into constant current mode and limits to 2A. The voltage is about 0.3V measured on the Samsung board. So ~0.15ohm, all the other regulator outputs are in the megaohm range.


"The LD1117AG can only supply about 800 miliamps, are you sure you have a short? , Does the input voltage to the regulator ic drop when the tv is turend on? If there was a short on the regulator's output, I would think the regulator ic would at least get hot but I can't see it shutting down the power supply."

That's a good point, but I don't have the TV here so can't easily test that. There could be more than one fault as well.

I think the short must be somewhere with very good heat sinking. Hopefully not the main IC.

[sean0118]

Re: Samsung Main Board - BN41-01800B

Ops I was misunderstanding the datasheet. The regulator is pin code A: GOI.

The short is on pin 3, so actually it's input rail, not the 1.8V output.


I did make some progress though, there's a Realtek RTL8201F ethernet driver which heats up about 5C above everything else. Turns out it's 3.3V inputs are shorted to GND. I guess the 1.8V regulator is powered from the 3.3V too.

[sean0118]

Re: Samsung Main Board - BN41-01800B

Good news, I removed the Realtek RTL8201F chip, the short is gone, now about 400ohms from the 3.3V rail to GND.


400 ohms seems a little low, but maybe it's normal, will put a new chip on and see what happens.


edit: That Realtek chip was horrible to remove, lead free solder and a centre gnd pad.