Samsung 60" LED blank screen and WILL NOT STAY OFF

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Both disconnected. Readings are with ONLY AC power cord plugged in.

1. B13V = 11.9v
2. PWM DIM = 4.01v
3. B13V = 12.2v
4. B14V = 12.1v
5. Vamp =12.1v
6. BLU ON = 3.52v
7. Vamp = 11.9v
8. GND
9. GND
10. GND
11. B5V = 5.6v
12. A5V = 5.6v
13. B5V = 5.55v
14. PS ON = 3.76v

I checked resistance again on the backlight cable to chassis while applying pressure all over the back of the chassis. Still found no change in resistance.

Also, because it's now a few pages back, I would like to reiterate that a boxelder bug was wrapped around two legs of the transformer when I first opened the TV (for this issue). I attached a picture to that post. No one said a word about it though, and I assumed it wasn't really an issue. I'm starting to wonder if maybe that was the real cause of this very strange problem. Could it have shorted the transformer, or something in circuit after it?

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Try with BOTH the backlight connector and cable to mainboard unhooked, plug the power cord into the powerboard, test voltage of pins on CNM803 compare them to the map/legend there printed on the board if that's all good it might be time to VERY carefully dig down to the backlights. The panel is VERY flimsy and easy to break, maybe check several youtube videos before hand, not exactly sure if backlights are the issue but these models are very prone to backlight failure.

I've replaced the backlights on this TV twice. First time was when I acquired it (they were bad), and the second time was because of the light spreaders falling off the new set. Shopjimmy RMAd them for me.

I'll check those voltages and report them back to you.

[nomoresonys]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Try with BOTH the backlight connector and cable to mainboard unhooked, plug the power cord into the powerboard, test voltage of pins on CNM803 compare them to the map/legend there printed on the board if that's all good it might be time to VERY carefully dig down to the backlights. The panel is VERY flimsy and easy to break, maybe check several youtube videos before hand, not exactly sure if backlights are the issue but these models are very prone to backlight failure.

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

With reference to the chassis?
They should all show NO resistance, also did you test when you move the panel around?

When you'd like me to check for alternate scenarios, it's easiest to know ahead of time so I can have that information ready. But no, I didn't move the panel around during this test. The meter I'm using (forcefully at this point) apparently isn't too trustworthy. For some reason it had an ambient resistance reading that bounced around heavily between 14ohms and 20ohms... Touching the two probes together brought it down to a more consistent 4ohms. Checking resistance of the plug did not vary at all from the 'ambient' readings. This i'd conclude, for the sake of this meter, that there is no resistance on the LED plug, at least at the time of measurement.

[budm]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Ok, well lesson learned.... Because I checked completely opposite of everything you said.

So, the meter I was using is toast now. The very-strange looking fuse that it DOES have inside looks fine/filament-unbroken.. so I reverted to the earlier questionable meter. However, checking resistance from each of the four wired pins of the LED connector, none had any change in resistance.

With reference to the chassis?
They should all show NO resistance, also did you test when you move the panel around?

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

How can you blow the meter fuse when the LCD connector is not in place? Are you testing the LED CONNECTOR that goes to the panel and that connector is NOT connected to the power supply board. There is NO Voltage on that LED connector when it is not connected to the power supply board.
Also do not test the resistance when the device is powered up.
https://www.badcaps.net/forum/attach...7&d=1578707669
Pull that LED connector with wires that go to the panel and then check the resistance of that connector with them wires on it, NOT the connector on the power supply board.

Ok, well lesson learned.... Because I checked completely opposite of everything you said.

So, the meter I was using is toast now. The very-strange looking fuse that it DOES have inside looks fine/filament-unbroken.. so I reverted to the earlier questionable meter. However, checking resistance from each of the four wired pins of the LED connector, none had any change in resistance.

[budm]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

How can you blow the meter fuse when the LCD connector is not in place? Are you testing the LED CONNECTOR that goes to the panel and that connector is NOT connected to the power supply board. There is NO Voltage on that LED connector when it is not connected to the power supply board.
Also do not test the resistance when the device is powered up.
https://www.badcaps.net/forum/attach...7&d=1578707669
Pull that LED connector with wires that go to the panel and then check the resistance of that connector with them wires on it, NOT the connector on the power supply board.

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

BTW, disconnect connector from the power supply board then check the resistance between chassis and each pin of the LED connector that goes to the LCD panel to see if any one of the pin shows resistance to the chassis or not.

I just attempted that and the very first pin I touched blew the multimeter (fuse?). The TV is fine however. I undoubtedly believe at this point that there is a short occurring somewhere within one of the LED strips. TV face down, power on, I reconnected the backlights.. Raised the set to a 30° angle and watched for about 10 seconds and it was working perfectly. Raised it upright to 45° and it went haywire again. This makes me think that one of the connections between LED strips is somehow arcing on the chassis.

[budm]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

BTW, disconnect connector from the power supply board then check the resistance between chassis and each pin of the LED connector that goes to the LCD panel to see if any one of the pin shows resistance to the chassis or not.

[budm]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

No, backlights were unplugged. Voltage jumps all over regardless of Standby when they are connected

That LED power supply boosted Voltage should not be there if the TV is in standby due to there will be no BL-ON to turn on the Boost converter. Something is not adding up.

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

402V with LED connector in place?

No, backlights were unplugged. Voltage jumps all over regardless of Standby when they are connected

[budm]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

"Old meter" = 123v
"New meter" = 94v

Guess I'm forced to revert back to the old one. I just don't want it to spark and blow the fuse again.

EDIT:
I just rechecked with the old meter and the voltages look correct now.

CP806 = 398v
CM861 = 402v
CM853 = 12.5v

I did not recheck with it in standby. I'm having trouble jumping PS_ON and working the multimeter at the same time. If it's necessary then I'll keep trying.

402V with LED connector in place?

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

probably more of a dumb question... But what function are you using on your meter... Ac or dc voltage?

dc

[budwich]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

"Old meter" = 123v
"New meter" = 94v

Guess I'm forced to revert back to the old one. I just don't want it to spark and blow the fuse again.

EDIT:
I just rechecked with the old meter and the voltages look correct now.

CP806 = 398v
CM861 = 402v
CM853 = 12.5v

I did not recheck with it in standby. I'm having trouble jumping PS_ON and working the multimeter at the same time. If it's necessary then I'll keep trying.

probably more of a dumb question... but what function are you using on your meter... AC or DC voltage?

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Based on your original post I would suspect the fault is with your main board. If the main board WAS working, it would issue the logic low and turn off the power supply, but it is not.
As for how the backlights operate without the main board connected, could be due to no PWM signal from the main board to properly control the led control ic.

Is there any diagnostic/repairs to be made to the main board or is it simply a replace-it scenario?

I'm not by any means an expert, but I really don't feel there anything wrong with the main board. I say this because of the following:

- With backlights unplugged, plugging in the TV it's in Standby

- Powering On (w/o BL), the TV operates normally ie I can change channels/inputs, volume, settings, everything works.

- Powers on and plays chime just fine, and also Powers off into Standby and stays as it should.

- I was able to even get into the Service Menu and Factory Reset as well as finish setup.

- Plugging in backlights INSTANTLY locks up the TV. Any menu that may have been on the screen disappears and every time it will display the No Signal message box. Even the 'snow' freezes on an analog channel.

Unless the main is trying to do something in regards to the backlights but can't?

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

you can do some simple tests of the meter using the wall plug as a "check". What do you read on the dc scale of your "new meter" when measuring the ac wall plug... that should indicate appropriately.

"Old meter" = 123v
"New meter" = 94v

Guess I'm forced to revert back to the old one. I just don't want it to spark and blow the fuse again.

EDIT:
I just rechecked with the old meter and the voltages look correct now.

CP806 = 398v
CM861 = 402v
CM853 = 12.5v

I did not recheck with it in standby. I'm having trouble jumping PS_ON and working the multimeter at the same time. If it's necessary then I'll keep trying.

[R_J]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Based on your original post I would suspect the fault is with your main board. If the main board WAS working, it would issue the logic low and turn off the power supply, but it is not.
As for how the backlights operate without the main board connected, could be due to no PWM signal from the main board to properly control the led control ic.

[budwich]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

you can do some simple tests of the meter using the wall plug as a "check". What do you read on the dc scale of your "new meter" when measuring the ac wall plug... that should indicate appropriately.

[x_orange90_x]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

Thats how it works. There is a pullup resistor on the PS_ON pin that turns ON the power supply when the main board is not connected. The only way to turn the power supply OFF is to have the PS_ON pin at a logic LOW. When the PS_ON is no longer grounded (Logic LOW) the pullup resistor, the pullup resistor on the power supply board, takes the PS_ON pin to 5volts (logic high) which turns the powersupply back ON.

Ok that makes sense. Thanks for clarifying that.

So what do you make of this scenario now? I've never seen an issue like this before. I was reading about other model Samsung that the backlights would flash or strobe, and people simply had to cut a jumper on the power supply and the flashing stopped. I think it was JP852 for one range of sizes and JP854 for another range. My power supply has neither, but I also don't think that would be the issue here anyway.

[R_J]

Re: Samsung 60" LED blank screen and WILL NOT STAY OFF

If I remove the jump it is instantly on again

Thats how it works. There is a pullup resistor on the PS_ON pin that turns ON the power supply when the main board is not connected. The only way to turn the power supply OFF is to have the PS_ON pin at a logic LOW. When the PS_ON is no longer grounded (Logic LOW), the pullup resistor on the power supply board, takes the PS_ON pin to 5volts (logic high) which turns the powersupply back ON.
As for the voltages measured by the meter, you better hope the reading is wrong or those capacitors are going to explode. CP806 is only rated for 450VDC. having 460~480vdc across them will cause them to fail