Samsung UN50RU7100fxza No Picture

[whiz62]

A buddy gave me this TV because it wouldn't come on. He had it mounted on his patio wall under the covered part but left it plugged in and the surge protector got filled with water and shorted out. It blew the cable box and then TV would only flash back lights from dim to full on repeatedly.

Power board fuse was good and all the SMD fuses I could find were also good.

Unplugging the the main board would fire up the back lights as normal. I have replaced the main board twice with ones off ebay and all works, sound, remote, etc. but no picture.

There are several versions of this TV. I have version DA01 and have matched the main board to correct version. I removed the bottom cover where the ribbon cables go down to the panel connections and see no evidence of water intrusion. There is no way to replace the two small boards in there as they are tab bonded to the panel and can find no fuses on them.

If anyone has any thoughts on this I would greatly appreciate it.

[neilc6]

Re: Samsung UN50RU7100fxza No Picture

Doesnt look like that model has a tcon. Normally if it does, the next test is to power up the the tv with only one side connected at a time. If you get picture on one side, then there is a panel fault on the bad side. Looks like you have panel with integrated tcon and the fault is in the panel or the attached boards. You can check if the fuse on the panel boards is blown and also check for shorted chip caps. You will need to remove the speakers, wifi module and covers to access.

[budwich]

Re: Samsung UN50RU7100fxza No Picture

check any / all labelled voltage points on the main board... hopefully at the connector between the power and main. Pictures are not clear enough to see the labelling.

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Thanks for the reply Budwich. Not much info that I can decipher on this main board. The bottom of power board does state pins 1 thru six grounds and voltages. 1and six should be grounds and 2,3,4,5 should be 12.35 v according to the power board. Here is what I have with readings of main.

power off: power on:
1= 0v 7= 0v
2= 12.94v 8= 2.587v
3= 12.92v 9= 3.245v
4= 12.92v 10= 3.298v
5= 12.92v 11= 0v
6= 0v 12= 0v

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Here are pics of connector top and bottom.

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Doesnt look like that model has a tcon. Normally if it does, the next test is to power up the the tv with only one side connected at a time. If you get picture on one side, then there is a panel fault on the bad side. Looks like you have panel with integrated tcon and the fault is in the panel or the attached boards. You can check if the fuse on the panel boards is blown and also check for shorted chip caps. You will need to remove the speakers, wifi module and covers to access.

Thanks for the reply. Removed cover to recheck the panel boards and cannot find anything that is labeled fuse. Will check the caps.

[budwich]

Re: Samsung UN50RU7100fxza No Picture

Thanks for the reply Budwich. Not much info that I can decipher on this main board. The bottom of power board does state pins 1 thru six grounds and voltages. 1and six should be grounds and 2,3,4,5 should be 12.35 v according to the power board. Here is what I have with readings of main.

power off: power on:
1= 0v 7= 0v
2= 12.94v 8= 2.587v
3= 12.92v 9= 3.245v
4= 12.92v 10= 3.298v
5= 12.92v 11= 0v
6= 0v 12= 0v

not sure I understand what your are showing with the table... "power off: power on" I see only one measurement for each pin???

some times you have to "follow" the pins to other boards for labels there... but also sometimes the darn manufacturers are just "lazy" in providing the "paint"... :-(

[budm]

Re: Samsung UN50RU7100fxza No Picture

Lets see the pictures of the tab bonding boards.

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

not sure I understand what your are showing with the table... "power off: power on" I see only one measurement for each pin???

some times you have to "follow" the pins to other boards for labels there... but also sometimes the darn manufacturers are just "lazy" in providing the "paint"... :-(

Well heck! Sorry, in a hurry. Here is pic of back of board. did not make any sense to me.

With tv plugged in and not turned on: taken from Main board connector.
pin 1=0v
pin 2=12.92v
pin3=12.92
pin4=12.92v
pin5=12.92v
pin6=0v
pin7=3.218
pin8=0v
pin9=0v
pin10=0.138v
pin11=0v
pin12=0v
With tv turned on:
pin1=0v
pin2=12.92v
pin3=12.92v
pin4=12.92v
pin5=12.92v
pin6=0v
pin7=2.587v
pin8=3.245v
pin9=3.298v
pin10=3.261v
pin11=0v
pin12=0v

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Lets see the pictures of the tab bonding boards.

Thanks Budm. You may need to tell this old man what area you need to see on these long puppies.

[budm]

Re: Samsung UN50RU7100fxza No Picture

https://www.badcaps.net/forum/attach...0&d=1579481627
There are many Voltage test points on the tab bonding boards, I.E. VDD, VDDAML, VGH, VGL, .....etc.

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Thank you sir!

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

I went back and removed the power board this time and it actually had a foot print of the 12 pin connector on the bottom and I screwed up big time on my readings previously. So sorry Budwich! I took budm's advise and looked for test points on the panel boards. Only one that I could positively identify was VDD and it read 3.273v.

Plugged in and power
off: on:
pin1 gnd=0v pin1=0v
pin2 ana-dim=0v pin2=2.587v
pin3 A13v=12.94v pin3=12.94v
pin4 D-on/off=0v pin4=3.245v
pin5 A13v=12.94v pin5=12.94v
pin6 blu-pwm=0v pin6=3.298v
pin7 A13v=12.94v pin7=12.94v
pin8 pwr on/off=0.138 pin8=3.261v
pin9 A13v=12.94v pin9=12.94v
pin10 gnd=0v pin10=0v
pin11 gnd=0v pin11=0v
pin12 gnd=0v pin12=0v

[nomoresonys]

Re: Samsung UN50RU7100fxza No Picture

Those readings look ok to me, looks like a mainboard issue.

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

Thanks for the reply nomoresonys!

[budwich]

Re: Samsung UN50RU7100fxza No Picture

Those readings look ok to me, looks like a mainboard issue.

not so fast.... op, you said that you replaced the main board twice... right? Do you still have the boards in hand? If so, try do the same measurements with another board to check results.
having said that, bad boards off ebay is a possibility all the time.

[budwich]

Re: Samsung UN50RU7100fxza No Picture

I went back and removed the power board this time and it actually had a foot print of the 12 pin connector on the bottom and I screwed up big time on my readings previously. So sorry Budwich! I took budm's advise and looked for test points on the panel boards. Only one that I could positively identify was VDD and it read 3.273v.

Plugged in and power
off: on:
pin1 gnd=0v pin1=0v
pin2 ana-dim=0v pin2=2.587v
pin3 A13v=12.94v pin3=12.94v
pin4 D-on/off=0v pin4=3.245v
pin5 A13v=12.94v pin5=12.94v
pin6 blu-pwm=0v pin6=3.298v
pin7 A13v=12.94v pin7=12.94v
pin8 pwr on/off=0.138 pin8=3.261v
pin9 A13v=12.94v pin9=12.94v
pin10 gnd=0v pin10=0v
pin11 gnd=0v pin11=0v
pin12 gnd=0v pin12=0v

there are some other voltages somewhere either at the main board or at the panel board (ie. labeling) as you need some panel drive voltages to make a picture... I think that the VDD only drives some of the board devices. At best check the areas around some of the "12v stuff" and try follow the traces towards the cabling going to the panel. Note: you don't need to do this under power as that could be dangerous for the board. You have identified the 12v stuff, use a resistance measurement to trace tracks following continuity along the way.

[nomoresonys]

Re: Samsung UN50RU7100fxza No Picture

NOT so fast budwich, OP DID you do test in post #2 ??

[whiz62]

Re: Samsung UN50RU7100fxza No Picture

I had already sent the first board back before I got this one but I did do the test on board #1 from the second post.

Just now did the test on #2 and got same results as #1, no change in panel.