Samsung UN55D7000 clicks but does not turn on

[stephentw]

Hello BADCAPers,

We came back from being on vacation for a week, and our TV, a Samsung UN55D7000LF, would not turn on. It just clicks every 10 seconds or so. I had a similar issue with my previous Samsung and just had to replace the caps, but on this TV I'm having no luck determining the root cause. Here's is what I have tried:

Model Info:

• All caps look fine
• Disconnected the main board from the SMPS board, all LED strips power on, no clicking in the power relay.
• Reconnected and disconnected the T-Con board, still clicking
• Replaced the SMPS board (no luck)
• Replaced the main board (no luck - returned it)
• Disconnected the speakers, wifi module, bluetooth module and touch sensitive control buttons. (no luck, still clicks)
• Replaced the IR module (no luck still clicks)

Red power light is illuminated when off, when I turn on with the remote the light double blinks 5 times and the relay above where the power plugs in clicks every ~10 seconds and the backlights never light and TV does not come on.

Any help anyone can provide is greatly appreciated.

[CapLeaker]

Re: Samsung UN55D7000 clicks but does not turn on

A set of hi res pictures of your main board and the PSU would be nice, also voltage measurement on all pins on the connector that goes from the PSU to the main board (on/off with pinout).
What does STBY voltage, PSon and BLon do?
What you can also do is to unplug the main board from the PSU and force the PSU on with a 1k resistor from STBY to PSon. See if the PSU comes up normally or not.

[stephentw]

Re: Samsung UN55D7000 clicks but does not turn on

Hello,

Attached are pics of the SMPS, Main and T-Con board. The pinout for the cable between the SMPS and the main board can be found on the 2nd page of this document:


I'll try to get voltages and power the SMPS board on as suggested as soon as I find the PSon points.

Thanks,
Stephen

[CapLeaker]

Re: Samsung UN55D7000 clicks but does not turn on

Measure all voltages in the 22 pin connector on the left in the first picture with pin out.

[budm]

Re: Samsung UN55D7000 clicks but does not turn on

Measure all voltages in the 22 pin connector on the left in the first picture with pin out.

+1, please make sure to put each Voltage reading after each pin number and pin names so we will know what is missing.

[tibimakai]

Re: Samsung UN55D7000 clicks but does not turn on

I had and still have one with this kind of issue and always ended up being the main board. PS_ON is not present or to low.
Usually, I remove the PS_ON wire and measure it, to see if it is present.

[stephentw]

Re: Samsung UN55D7000 clicks but does not turn on

Thank you all for your support, I have a few n00b questions:

1. I can't get contacts with my volt meter on the either the SMPS or the main board side while the cable is connected. If I unscrew the main board to make the measurements across the bottom, will it affect the pin-out readings, meaning will it affect the grounding?

2. What is the PS_ON wire, I don't see a wire with this label in the 22 wire pin-out. Ref.: pg2:

[budm]

Re: Samsung UN55D7000 clicks but does not turn on

So per info from the the service manual, when you disconnect the CN201 wire harness per service manual, do you get the backlights to come on and stay on? That will tell you if you have main board or power supply board problem which you have already done that.
Pin 2 on the CN201 is the PS-ON pin, but do the test by disconnecting the cable.
To me that new main board you got may be defective or it is not the correct one.

[CapLeaker]

Re: Samsung UN55D7000 clicks but does not turn on

What is PSon? That is the voltage needed coming from the main board to turn all of the PSU on. So 5V STBY comes from the PSU and that is always there. When you turn on the TV, the main board returns PSon and BLon to the PSU and all the voltage rails and back light are on.
So that's why we ask a lot: What does PSon and BLon do and if the STBY voltage is present.

[stephentw]

Re: Samsung UN55D7000 clicks but does not turn on

Yes, all the backlights work when the SMPS board is disconnected from the main. Attached is a list of all voltages measured while ground the black lead to the tv. The bottom two pins correspond to pins 1 and 2 on the SMPS board.

Which pins are STBY and BLon? ...I don't see them labeled this way on the pin-out in the above link.

Thanks...

[budm]

Re: Samsung UN55D7000 clicks but does not turn on

Look at the power supply board CNM803 Pin 20 (POWER_ON/OFF), PIN 12 is the BL-ON (BLU_ON/OFF) as shown on the connector of the power supply.

[CapLeaker]

Re: Samsung UN55D7000 clicks but does not turn on

Yes, all the backlights work when the SMPS board is disconnected from the main. Attached is a list of all voltages measured while ground the black lead to the tv. The bottom two pins correspond to pins 1 and 2 on the SMPS board.

Which pins are STBY and BLon? ...I don't see them labeled this way on the pin-out in the above link.

Thanks...

Everything is there...
How come the connector is damaged? Does the damaged pin make contact with the board?

[budm]

Re: Samsung UN55D7000 clicks but does not turn on

I thought he marked it with the black marker, if not it looks burnt.

[CapLeaker]

Re: Samsung UN55D7000 clicks but does not turn on

I thought he marked it with the black marker, if not it looks burnt.

I can't tell if it's burnt or just marked.

[stephentw]

Re: Samsung UN55D7000 clicks but does not turn on

No, it's not burnt, it's sharpie. It was there when I disassembled.

[stephentw]

Re: Samsung UN55D7000 clicks but does not turn on

Hello All,

Thanks for your help thus far. i'm still trying to isolate what the problem is so I can order replacement parts. It seems the first SMPS board I ordered was in fact bad, because the backlights would not come on when there was no connection to the main board. My original SMPS board does however power on the back lights, so I have no indication that it is faulty as of yet.

I was trying to make sense of CapLeaker's remark about the 1k resistor. Please help to get me on track.

• Is my assumption about the pinout correct on the attached connector going to the main board? (Pin 1 is on top row toward the bottom of the tv, pin 2 directly beneath on bottom?)
• Should I connect Pin 2 and 4 with the 1k resistor before plugging in power or after? And what am I expecting to see different since the back light will come on with the cable disconnected?

Thanks!

[budm]

Re: Samsung UN55D7000 clicks but does not turn on

"My original SMPS board does however power on the back lights, so I have no indication that it is faulty as of yet" so there is no need to try to force on the SMPS.

[Uzrnaim]

Re: Samsung UN55D7000 clicks but does not turn on

Sorry to dig this up, but I've got a very similar situation and felt this is a good place to start.

I've got the same unit right now, and I'm getting the relays clicking on and off every few seconds. I unplug the connector which leads to the main board from the power supply, and the clicking stops. From what I read above my LED backlight should light at this point, but I'm getting no light at all. I already replaced all of the electrolytic capacitors, but I'm still getting no backlight when the main board isn't connected and still getting the relay clicks when I do plug in the main board again.
Do you think it's more likely a bad panel or another part of the power supply has failed?

[michael dranfield]

Re: Samsung UN55D7000 clicks but does not turn on

Sorry to dig this up, but I've got a very similar situation and felt this is a good place to start.

I've got the same unit right now, and I'm getting the relays clicking on and off every few seconds. I unplug the connector which leads to the main board from the power supply, and the clicking stops. From what I read above my LED backlight should light at this point, but I'm getting no light at all. I already replaced all of the electrolytic capacitors, but I'm still getting no backlight when the main board isn't connected and still getting the relay clicks when I do plug in the main board again.
Do you think it's more likely a bad panel or another part of the power supply has failed?

Just above where the mains goes into the power board there is a black relay lying on its side, I have had this cause exatcley the problem you have , it had burnt contacts.

[Uzrnaim]

Re: Samsung UN55D7000 clicks but does not turn on

Sorry to dig this up, but I've got a very similar situation and felt this is a good place to start.

I've got the same unit right now, and I'm getting the relays clicking on and off every few seconds. I unplug the connector which leads to the main board from the power supply, and the clicking stops. From what I read above my LED backlight should light at this point, but I'm getting no light at all. I already replaced all of the electrolytic capacitors, but I'm still getting no backlight when the main board isn't connected and still getting the relay clicks when I do plug in the main board again.
Do you think it's more likely a bad panel or another part of the power supply has failed?

Let me clarify what I've done.
TV came to me, clicking relay no life other than that.
I measured voltages on outputs, everything was close to the spec
I disconnected the line to the main board, no clicking any more, but no backlight
Disconnect panel connections and connect main board, I get clicking
I re-capped all of the electrolytics, same exact symptoms as before.

Relay connects for ~2 seconds, then remains disconnected for ~7 seconds, and repeats indefinitely.