Samsung LE40B620R3W shuts down

Ukdigger · 10-15-2020, 07:15 AM

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

**nomoresonys** · 10-15-2020, 07:57 AM

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.

**dick_barton** · 10-15-2020, 08:39 AM

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?

Ukdigger · 10-15-2020, 09:03 AM

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]

Ukdigger · 10-15-2020, 09:12 AM

Ukdigger · 10-15-2020, 09:13 AM

**dick_barton** · 10-15-2020, 12:33 PM

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.

**nomoresonys** · 10-15-2020, 09:47 PM

I think the mainboard isn't sending the proper signal/s.

Ukdigger · 10-16-2020, 01:05 AM

https://www.badcaps.net/forum/attach...1&d=1602832478

Ukdigger · 10-16-2020, 01:19 AM

The board number is BN44-00264A. I only tested the pins that had wires coming from them.

**vinceroger69** · 10-16-2020, 01:25 AM

Quote:

Originally Posted by Ukdigger

The board number is BN44-00264A. I only tested the pins that had wires coming from them.

psu schematic

**nomoresonys** · 10-16-2020, 04:36 AM

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.

Ukdigger · 10-16-2020, 04:57 AM

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

**dick_barton** · 10-16-2020, 07:22 AM

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.

Ukdigger · 10-16-2020, 09:28 AM

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

**dick_barton** · 10-16-2020, 09:51 AM

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.

**budm** · 10-16-2020, 02:31 PM

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?

**nomoresonys** · 10-16-2020, 03:33 PM

Quote:

Originally Posted by budm

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.

Ukdigger · 10-17-2020, 02:34 AM

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.

Ukdigger · 10-19-2020, 03:31 AM

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

10-15-2020, 07:15 AM	#1
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	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

10-15-2020, 07:57 AM	#2
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 7,868	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.

10-15-2020, 08:39 AM	#3
dick_barton Badcaps Veteran Join Date: Aug 2015 City & State: Cardiff My Country: Wales Line Voltage: 230V AC, 50Hz I'm a: Hobbyist Tech Posts: 6,544	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? __________________ Willing to help but I'm no expert.

10-15-2020, 09:12 AM	#5
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	Re: Samsung LE40B620R3W shuts down

10-15-2020, 09:13 AM	#6
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	Re: Samsung LE40B620R3W shuts down

10-15-2020, 09:47 PM	#8
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 7,868	Re: Samsung LE40B620R3W shuts down I think the mainboard isn't sending the proper signal/s.

10-16-2020, 01:19 AM	#10
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	Re: Samsung LE40B620R3W shuts down The board number is BN44-00264A. I only tested the pins that had wires coming from them.

10-16-2020, 04:36 AM	#12
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 7,868	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. __________________ (Signature) One of the first and least expensive things you can do when you have an issue is take the powerboard out of the tv, flip it over and look the solder joints over with a magnifying glass if needed, add a little flux to make the solder flow well and add solder to any joints that look even a little suspect. You can practice on a scrap pcb board if needed, careful not to bridge any joints, and always let the board sit for quite a while or discharge the big caps with an appropriate resister before working on it (safety first) to try to keep from getting shocked, it doesn't take 1000 volts to KILL, a lot less can kill, so be careful, it's only a tv.

10-16-2020, 04:57 AM	#13
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	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

10-16-2020, 07:22 AM	#14
dick_barton Badcaps Veteran Join Date: Aug 2015 City & State: Cardiff My Country: Wales Line Voltage: 230V AC, 50Hz I'm a: Hobbyist Tech Posts: 6,544	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.

10-16-2020, 09:51 AM	#16
dick_barton Badcaps Veteran Join Date: Aug 2015 City & State: Cardiff My Country: Wales Line Voltage: 230V AC, 50Hz I'm a: Hobbyist Tech Posts: 6,544	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..

10-16-2020, 02:31 PM	#17
budm Badcaps Veteran Join Date: Feb 2010 City & State: S.F. Bay area My Country: USA Line Voltage: 120V 60Hz I'm a: Knowledge Seeker Posts: 39,206	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? __________________ Never stop learning Basic LCD TV and Monitor troubleshooting guides. http://www.badcaps.net/forum/showthr...956#post305956 Voltage Regulator (LDO) testing: http://www.badcaps.net/forum/showthr...999#post300999 Inverter testing using old CFL: http://www.badcaps.net/forum/showthr...er+testing+cfl Tear down pictures : Hit the ">" Show Albums and stories" on the left side http://s807.photobucket.com/user/budm/library/ TV Factory reset codes listing: http://www.badcaps.net/forum/showthread.php?t=24809

10-17-2020, 02:34 AM	#19
Ukdigger Member Join Date: May 2020 City & State: Lincolnshire My Country: England I'm a: Knowledge Seeker Posts: 61	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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