Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

[ALR]

I purchased a Samsung un55b8000fxza from someone today for a good price in hopes it would be an easy repair so I can just upgrade my 52" but it's looking like a Mainboard issue.

http://www.shopjimmy.com/samsung-bn9...b8000xfxza.htm

No standby light, just relay clicking on/off. Removed Mainboard from power supply and I got backlight. I've removed everything on the mainboard and left the mainboard to PSU cable connected and still same results so I'm pretty sure it's the main board that's the only issue. Just not sure what usually goes out on Mainboards.

What they told me was lightning took out their entire electronics in the home due to a strike but the TV worked fine for about until a month after. Since then, it won't power on.

I can't really find these boards available and the ones I do find are at least $200-$300. I paid $40 for this thing, I'm hoping someone can help me track down the issue on the mainboard so I can try swapping out some components!!

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

I have found a free repair manual for this model.

http://www.wiringdiagrammanual.com/e...id=659885#ecms

I have checked the CNM802 pins on the power supply

1--pwr on/off---
3--standby 5.2v----5.2v
5--GND
7--18v---17v
9--GND
11--GND
13--5.3v--5.1v
15--5.3v--5.1v
17--GND
19--12v---12.7v
21--12v---12.7v
23--BL on/off----000's out/clicks/jumps to 13mV
25--P DIM----3.3v
27--120vsens---n/a
29--N.C-----n/a


I followed the troubleshooting schematic for the mainboard and tested a few IC's. I posted a SS of the repair manual





When it got to the IC205, IC208 & IC210, I had one IC that didn't read what it should have. IC210, it 000'd out when there should have been 3.3v on PIN 1.

At this point, is it safe to assume replacing this IC should fix the problem and should I do what it says and replace all 3?

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

It looks like it's a 3.3v 1A LDO voltage regulator. I can't seem to find a replacement one anywhere. Would this voltage regulator being possibly bad, cause the standby voltage to not show and the relay clicking/not fully powering on?

Seems to be Seiko
S-1172B 33-VJ3 6015

I found this and it looks like what I need and it's a 3.3v but the ending numbers are off and no one has stock it seems.

S-1172B33-E6T1G

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

No Vout, but what do you have at Vin? IC210 picture is not big enough to tell what it looks like, it may be the same 1117 series regulator. Also check if the output has shorted to ground.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Vin is showing 5.1v

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Check the resistance between output pin and ground. Do you have the picture of this LDO?

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Is it like this? There is an ON/OFF control pin.
http://www.mouser.com/ProductDetail/...vqFrGwBkcKI%3d

https://cdn.badcaps-static.com/pdfs/...0c7d1441c1.pdf

You have 'B' type: LO = OFF, HI = ON.
ON/OFF pin
This pin starts and stops the regulator.

When the ON/OFF pin is set to OFF level, the entire internal circuit stops operating, and the built-in P-channel MOS
FET output transistor between the VIN pin and the VOUT pin is turned off, reducing current consumption
significantly. The VOUT pin is set to the VSS level by the internal dividing resistor of several hundred kΩ between
the VOUT pin and the VSS pin.
Note that the current consumption increases when a voltage of 0.3 V to 1.0 V is applied to the ON/OFF pin.
The ON/OFF pin is configured as shown in Figure 14. Since the ON/OFF pin is neither pulled down nor pulled up
internally, do not use it in the floating status. When not using the ON/OFF pin, connect it to the VSS pin in the
product A type, and connect it to the VIN pin in B type.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Yes, it looks like that on/off pin and when I saw that, made me wonder if this is the root cause of it not fully turning on. Let me check the resistance real quick

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

You have 'B' type: LO = OFF, HI = ON.
ON/OFF pin
This pin starts and stops the regulator.

When the ON/OFF pin is set to OFF level, the entire internal circuit stops operating, and the built-in P-channel MOS
FET output transistor between the VIN pin and the VOUT pin is turned off, reducing current consumption
significantly. The VOUT pin is set to the VSS level by the internal dividing resistor of several hundred kΩ between
the VOUT pin and the VSS pin.
Note that the current consumption increases when a voltage of 0.3 V to 1.0 V is applied to the ON/OFF pin.
The ON/OFF pin is configured as shown in Figure 14. Since the ON/OFF pin is neither pulled down nor pulled up
internally, do not use it in the floating status. When not using the ON/OFF pin, connect it to the VSS pin in the
product A type, and connect it to the VIN pin in B type.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Starts out about .001 or something like that and slowly goes up to .005, relay clicks, OL then 4. ohms

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Kind of confusing but I think I got it. What does it mean when it says when not using the on/off pin 3, connect it to the Vin pin 6?

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

IF you do not want to have ON/OFF function, the tie the ON/OFF pin to the Vin pin so the regulated output will always be present.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

So basically you would have to unplug the set but if I solder a wire to the two pins, if this one IC is my problem and it turns on, replacing this would fix the issues all together?

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

You have to find out if that ON/OFF pin is being used or not, if it shows 0V then the circuit some where else is not sending the signal to turn on this regulator, so it is not the regulator fault if it does not get the signal.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Okay, got ya. I just checked Pin 3 for the ON/OFF and when the relay clicked, it jumped to 1.3v

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Then it drops down? Per spec sheet, the minimum for on is 1V.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Yes, it starts at 000.5 or so mV and when it clicks, it goes to 1.3v and then back down to mV

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Then you should be able to see the output spike up for second also, but it sounds like the controller problem.

[ALR]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

Yeah, it spikes up to 385. mV from 000.1 when the relay clicks. Which one is the controller? Is there a way to test that?

[budm]

Re: Samsung UN55B8000F Mainboard Issue(Relay Clicking Issue)-Help!!

You need to trace out the ON/OFF pin to see where it goes. Does the service manual have the main board diagram? It may have gone into shutdown due the error some where in the circuit.
Main board repair down to component level is not going to be easy, especially when damaged is done by surge/lighting.