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Old 11-27-2021, 02:20 PM   #1
rgla
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Default Samsung UN65MU8000FXZA Dead NO power NO standby light won't turn on

Hi. First time post. I've scoured the previous forums looking for info - there isn't much for my model
UN65MU8000FXZA

We had a power outage. Everything plugged into the Monster surge protector seems to be fine except my Samsung TV. It was dead when the power came back to the house.

Here's what I've looked at:
Unplugged main board from power supply - BACKLIGHTS COME ON.

Ordered new main board - still didn't work. Not sure if used MB was DOA

MAIN BOARD = BN94-12295K
PSB= BN44-00912 L65E8NR_MHS

There doesn't seem to be a pin for Standby like on other boards
The value on pin 16. power on/off seems high but what do I know.

Please help me diagnose - is the power supply board done?

Here are the values I tested for VOLTS. I didn't have the needle tips for multimeter so made my own but here are the values
WITH = with MB connected
WO = without MB connected

CNM803 WITH WO
1. GND 0 0
2. GND 0 0
3. GND 0 0
4. GND 0 0
5. VAMP 9 12.85
6. GND 0 0
7. VAMP 9 12.85
8. OD_LEVL 0 3.2
9. VAMP 9 12.85
10 FAIL COUNT 0 13
11 A13V 9 12.85
12 OD ON OFF 0 3.2
13 A13V 9 12.85
14 BLU 0 3.2
15 A13V 9 12.5
16 POWER ON/OFF 96 4.5
17 A13V 9 12.85
18 GND 0 0
19 GND 0 0
20 GND 0 0

Last edited by SMDFlea; 12-01-2021 at 05:22 AM.. Reason: UN65MU8000FXZA
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Old 11-27-2021, 04:34 PM   #2
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

16 POWER ON/OFF 96 4.5? 96vdc?
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Old 11-28-2021, 07:28 AM   #3
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Maybe 96mV?
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Old 11-28-2021, 10:57 AM   #4
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

What voltages does the old mainboard have? Seems the mainboard is pulling down your 13v line.
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Old 11-28-2021, 11:04 PM   #5
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Yes the 96 is VDC. I didn't move the Meter to another setting.
It seemed high to me. This was only when the cable from PB to MB was disconnected. There's actually 2 cables running from PB to MB.

I got another mainboard today but it was one letter off
BN94-12295K (original board) BN94-12295J - new board. The backlights started flashing and I think the standby light was flashing. The repair shop said it must be the MB but I'm not convinced. He wasted to solder a part from the J board to my K board and said it would probably work.

I don't want to buy a new MB and have the PB fry it.
This did happen after a power outage so maybe it was a one time surge?

Thanks for the help
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Old 11-28-2021, 11:10 PM   #6
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

I'm pretty new to this so excuse this question.
I did find a "pin" in the middle of the power board that says "stndby" 7.5 ON 11
Not sure what this is called - a pin? it looks almost like a staple that's about an inch long. How do I test this? set meter to VDC, Ground the black meter probe to the body of the TV and touch the red probe to the staple/pin (it's in the middle of the board and doesn't have a cable or anything near it.
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Old 11-29-2021, 10:23 AM   #7
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Need some pictures of connectors and boards.
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Old 11-29-2021, 10:39 AM   #8
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Here are the images.
Thanks for the help.
Attached Images
File Type: png Screen Shot 2021-11-29 at 8.32.31 AM.png (469.3 KB, 17 views)
File Type: jpg bn94-12295k MB.jpg (953.9 KB, 23 views)
File Type: jpg IMG_0641 2.jpg (742.4 KB, 19 views)
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Old 11-29-2021, 01:07 PM   #9
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

You can measure the voltage on that link and see if it is at 7.V volts when in standby and 11.8V when out of standby. Meter set to dc voltage and can use the chassis as ground.
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Old 11-30-2021, 10:50 AM   #10
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Thanks for the follow up help. Here are the voltages I got on the standby link (jumper?) (HOT side of board)
The TV was not ON. It was just plugged in. It won't turn on so I'm not sure how to assess the info from the board:
According to the board it should be 7.5 standby and 11.8 on.

With the main board connected the voltage was 9v
Withe the main board DISCONNECTED the voltage was 12.85

somewhat similar to what I was getting at the cable connection pins.
Still not sure if the power on/off connection cable pin is supposed to be 96 and then down to 4.5
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Old 11-30-2021, 11:15 AM   #11
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

That does not appear to be hot side. All voltages on that side taken from cold side ground as on pads for screw holes.
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Old 11-30-2021, 11:24 AM   #12
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

This maybe worth a read
https://masterelectronicsrepair.blog...amsung_98.html
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Old 11-30-2021, 11:44 AM   #13
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Sorry. You are correct. This is on the COLD side.
I put the black probe in a screw hole on the chassis of the tv.
Does any of that matter for the reading?
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Old 11-30-2021, 11:55 AM   #14
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Hot side ground and cold side ground are 2 different things. Your voltage readings are odd. As in 96v doesn't seem valid. Are your batteries good in your voltmeter?
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Old 11-30-2021, 08:21 PM   #15
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

All the voltage readings I took were on the cold side. I grounded to a screw hole / chassis in the back of the TV.
New batteries, new multimeter.

It seems like the other readings were fine so I suspect the 96 is a correct reading. As soon as I disconnect the main board it goes down to 4.5

Why would the standby jumper pin not measure 7.5 or 11.8?
With the main board connected the voltage was 9v
Withe the main board DISCONNECTED the voltage was 12.85
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Old 11-30-2021, 10:16 PM   #16
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Are those voltages with old mainboard or new? Are you sure pin 16 was not .96vdc.
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Old 11-30-2021, 10:18 PM   #17
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Old mainboard. I don't have the new one yet. Hard to find and even harder to find someone who wants to look into the problem with the board and fix it.
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Old 11-30-2021, 10:37 PM   #18
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Seems you have a bad mainboard.
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Old 12-01-2021, 03:07 AM   #19
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Quote:
Originally Posted by rgla View Post
Old mainboard. I don't have the new one yet. Hard to find and even harder to find someone who wants to look into the problem with the board and fix it.
This is the only site i can see who has any in stock not cheap though
https://www.tvpartstoday.com/BN94-12...n94-12295k.htm
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Old 12-01-2021, 04:16 AM   #20
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Default Re: Samsung 65 Dead NO power NO standby light won't turn on

Most likely, the firmware of the standby mode IC1604 25Q40 flew off, as always in the "MU" series. Do you have main BN41-02570B?
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