Samsung LNS3251DA won’t power on, no sound, no standby light-power board problems

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

I got this resistor removed from the board and it definitely reads 00.0 and I put the meter on diode test and it beeps for a short. I understand the reasoning, it should be open circuit but it is shorted for sure.

[dick_barton]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

RM803 is given as 0.2 Ohms, 5 Watts in the schematic budm provided in post #13

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

I got this resistor removed from the board and it definitely reads 00.0 and I put the meter on diode test and it beeps for a short. I understand the reasoning, it should be open circuit but it is shorted for sure.

When it is blown it will go open circuit, if it is good then it show really Low Ohm, that resistor (RM803) is fine.
So it is not showing as open circuit (high resistance), right?
But RM801 is shown as open circuit, right?

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

I understand what you are saying but this resistor has a reading of 00.0 and not a point higher. I have some other ones and I tested them just to be sure and my others test fine. This resistor is shorted and NOT an open circuit.

My resistor at RM803 is printed 2K 5W, doesn't that mean it is 2,000 Ohms?

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Are you using 200 Ohm scale on your meter? And what resistance does the meter show when you touch the two meter probe together? I will doubt that your meter can show 0 Ohms for the probe resistance unless it has 0 Ohm adj.

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

My meter is auto range and when I touch the probes together it reads 00.0 as shown in this picture.

So does R2K mean? 2K Ohms or 0.2 Ohms?

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Man your probe wires has no resistance at all? Hard to believe. So it is on the lowest Ohm scale range?
But any way, the marking on the resistor that has 'R' in the marking for example
1RJ = 1 Ohm, J = 5%
1RK = 1 Ohm, K = 10%
R47J = 0.47 Ohm, J = 5%
R2K = 0.2 Ohm, K = 10%

For example, 0.22 Ohm resistor 5W 5%: SSR5W-R22J
https://www.tedss.com/2021011601

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

OK, so my resistor is a 0.2 Ohm 10% Tolerance. Great, thanks for the help. And I am assuming you are agreeing that the one I have is defective? I will look through my stuff for one before I buy.

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

OK, so my resistor is a 0.2 Ohm 10% Tolerance. Great, thanks for the help. And I am assuming you are agreeing that the one I have is defective? I will look through my stuff for one before I buy.

You are talking about the 0.2 Ohm resistor? I never have those type of resistor shorted out before and I do not think your probe's wire resistance is also 0 Ohm, if it fused shorts then you definitely have shorted parts in that IC. You can replace the resistor just to reduce the doubt.
You still need to check the IC that I mention earlier to see if it is shorted or not.

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

I did check all the ICs on the board. I even looked up the Data sheets for them so I would know where the ground was. And as far as I could tell there was no shorts anywhere except the RM803 resistor.

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

OK, I hope you are correct that IC IC801S is OK.

[Shane711]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

OK, well I got good news. The TV is alive and working good.

My friend had RM801 so I put that in.
As far as RM803 well I guess I made a mistake, apparently my meter is not dependable enough on it own. You guys were right. I took my meter out of Auto Range and set it to the lowest setting and the 0.2 Ohms resistor was reading 0.1 Ohms. I decided to test it out. And yes, I was correct about the IC not being shorted. The Power Board was up and running. But then the backlights would turn on for 2 seconds and turn off. I'm like "NO, What now?" So I was testing the voltages going to the inverter board and they were good and holding steady. So I figured a problem with the inverter board or the lamps. Looking over the inverter board I found a broken solder connection on one of the transformers, I resoldered that and touched up some others. Now the TV is working 100%

The final verdict is 4 bad caps, 1 bad resistor at RM801 and a broken solder connection on the inverter board.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Hi,
many years later... same problem here.
RM801 is burned.

I don't know how to check if ICM801S is OK.

I'll try to replace RM801 for now.

[R_J]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

It is very likely the ic is also shorted, RM801 acts like a fuse for the supply voltage for the ic, if the ic (internal mosfet) shorts, RM801 opens.
Check the internal (Q2 and Q1) fets they may or may not be shorted

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

How can I check it without desoldering it, and without external interference ?

[R_J]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Get a multimeter and with the meter in diode test or use the lowest resistance range, check between the pins of the ic. I gave you a pinout of the ic. If the internal fets are shorted they will show shorted.
If you can't tell, replace the resistor and power it up, if the resistor blows again the ic is bad.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Just checked. Seems to be shorted !

I have already ordered resistor, so I'll try the easy way first.
Then, I will order the IC and change it. I'm pretty sure I'll have to.

Thanks.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Hi again.
Waiting for replacing parts, I have checked all capacitors on the board.
Two of them are bulged : CM858 and CM860.
I plan to replace them too.

Do you think it's appropriate to replace the other capacitors, as a precaution?
I read somewhere that CapXon capacitor are low quality.
However, television has worked well for almost 15 years.

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Sure replace all the round electrolytic caps, 15 years is a pretty good run.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Hi,

Today, I've replaced all electrolytic caps, and upgraded them :
100V instead of 63V
63V instead of 50V
50V instead of 25V
25V instead of 10V, and so on.

You can see attached picture :
bulged CM858 and CM860
small leak on CP803

And 3 others pictures :
with original caps
electrolytic caps, RM801 and ICM801S removed
with all components replaced

After that, I've replaced fuse and reinstalled the board on TV.
But... fuse fused again !
After more checks, I realized that I had used the wrong fuse : reading too fast, I installed a 3A instead of a 6.3A !

I plan to order right one, but I have a question :
Do I have to use time delay fuse, or fast acting one ?

Thanks.