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Old 10-15-2020, 07:15 AM   #1
Ukdigger
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Default Samsung LE40B620R3W shuts down

Samsung LE40B620R3WQXU
I'm thinking that the main board may be faulty, I would appreciate any help to test and fix it.
The TV works for about 2 minutes and then shuts down with no standby light. When the main board is disconnected the back lights come on and the TV stays on until powered off.

Voltages on power board

Main board disconnected
4.88
4.88
2.74
12.07
12.07
0
5.01
5.01
0
0
12.07
0
5.01
0.76

Main board connected
4.88
4.88
2.74
12.23
12.23
0
4.95
4.95
0
0
12.23
0
4.95
0.75
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Old 10-15-2020, 07:57 AM   #2
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Default Re: Samsung LE40B620R3W shuts down

Is there a legend/label on the board describing the pins and the number of the pin?, you put the voltage but we have no way of knowing what it is, so you want to do like, pin 1: ps on 3.3 volts, pin 2 etc. etc.
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Old 10-15-2020, 08:39 AM   #3
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Default Re: Samsung LE40B620R3W shuts down

Post pictures of your power supply board and of the legend as nomoresonys suggests, What is the part number of the power supply BN44-xxxxxx?
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Old 10-15-2020, 09:03 AM   #4
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Default Re: Samsung LE40B620R3W shuts down



Voltages on power board

Main board disconnected
pin 29 0
pin 27 4.88
pin 25 4.88
pin 23 2.74
pin 21 12.07
pin 19 12.07
pin 17 0
pin 15 5.01
pin 13 5.01
pin 11 0
pin 9 0
pin 7 12.07
pin 5 0
pin 3 5.01
pin 1 0.76

Main board connected
pin 29 0
pin 27 2.68
pin 25 1.79
pin 23 2.74
pin 21 12.23
pin 19 12.23
pin 17 0
pin 15 4.95
pin 13 4.95
pin 11 0
pin 9 0
pin 7 12.23
pin 5 0
pin 3 4.95
pin 1 0.76

[IMG]file:///C:/Users/Mick/Desktop/WP_20201015_15_11_11_Pro[1].jpg[/IMG]
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File Type: jpg WP_20201015_15_11_11_Pro[1].jpg (211.1 KB, 73 views)
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Old 10-15-2020, 09:12 AM   #5
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Default Re: Samsung LE40B620R3W shuts down

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Old 10-15-2020, 09:13 AM   #6
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Default Re: Samsung LE40B620R3W shuts down

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Old 10-15-2020, 12:33 PM   #7
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Default Re: Samsung LE40B620R3W shuts down

Your photo is difficult to read. It would make easier reading to list them similar to below. Where are all the even number listings.ie pins 2, 4, 6 ....28
Also what is the board number.
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Last edited by dick_barton; 10-15-2020 at 12:38 PM..
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Old 10-15-2020, 09:47 PM   #8
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Default Re: Samsung LE40B620R3W shuts down

I think the mainboard isn't sending the proper signal/s.
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Old 10-16-2020, 01:05 AM   #9
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Default Re: Samsung LE40B620R3W shuts down

https://www.badcaps.net/forum/attach...1&d=1602832478
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Last edited by Ukdigger; 10-16-2020 at 01:21 AM..
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Old 10-16-2020, 01:19 AM   #10
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Default Re: Samsung LE40B620R3W shuts down

The board number is BN44-00264A. I only tested the pins that had wires coming from them.
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Old 10-16-2020, 01:25 AM   #11
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Default Re: Samsung LE40B620R3W shuts down

Quote:
Originally Posted by Ukdigger View Post
The board number is BN44-00264A. I only tested the pins that had wires coming from them.
psu schematic
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Old 10-16-2020, 04:36 AM   #12
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Default Re: Samsung LE40B620R3W shuts down

Recheck pin 1, check it with everything hooked up, all boards connected, check in standby which is tv plugged into power but not turned on, which looks like you have .76 v, keeping probes in place hit power button on tv, see if that voltage changes, usually it should be around 3.3 steady v, when tv on and working properly.
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Old 10-16-2020, 04:57 AM   #13
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Default Re: Samsung LE40B620R3W shuts down

I did what you said and I get 0 volts in standby and when the power button is pressed it shoots up to 0.76 volts
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Old 10-16-2020, 07:22 AM   #14
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Default Re: Samsung LE40B620R3W shuts down

The ON/OFF is connected to the 5.3V Standby rail via RM882 so should be several volts when the mainboard is diconnected from the power supply.
I would measure the dc voltage on the 3 pins of QM802.
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Old 10-16-2020, 09:28 AM   #15
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Default Re: Samsung LE40B620R3W shuts down




As you look at my photo, I'm getting 0.06 volts of the left pin, 0 volts top right pin and 0.67 volts on the bottom right pin
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Old 10-16-2020, 09:51 AM   #16
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Default Re: Samsung LE40B620R3W shuts down

I think this is an always on power supply. If with the power supply disconnected from the mainboard you jumper a 1K resistor from ON/OFF to ground can you check that only the +5V stanby is running and the other supplies are off.

If this is the case then you probably do have a mainboard fault.

Last edited by dick_barton; 10-16-2020 at 09:52 AM..
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Old 10-16-2020, 02:31 PM   #17
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Default Re: Samsung LE40B620R3W shuts down

PS-ON of 0.76V is fine since the Base resistor RM864 is only 200 Ohms and RM882 pull-up is 10K.
The circuit is working otherwise you will not have switched 13V right now.
So the question is what are the Voltages at the connector when TV goes into shutdown after 2 minutes?
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Old 10-16-2020, 03:33 PM   #18
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Default Re: Samsung LE40B620R3W shuts down

Quote:
Originally Posted by budm View Post
PS-ON of 0.76V is fine since the Base resistor RM864 is only 200 Ohms and RM882 pull-up is 10K.
The circuit is working otherwise you will not have switched 13V right now.
So the question is what are the Voltages at the connector when TV goes into shutdown after 2 minutes?
Ok then, my bad.
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Old 10-17-2020, 02:34 AM   #19
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Default Re: Samsung LE40B620R3W shuts down

When using 1K resistor from ON/OFF to ground all other voltages were 0 volts, only +5V standby was on. The TV has been working normally now for about 30 minutes. When it goes off again I will test all the voltages and report back.
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Old 10-19-2020, 03:31 AM   #20
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Default Re: Samsung LE40B620R3W shuts down

TV was working normally until this morning and then went off with no standby light. Here are the voltages.

https://www.badcaps.net/forum/attach...1&d=1603099828
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File Type: jpg TV pins 2.jpg (32.4 KB, 9 views)
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