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Old 10-13-2010, 09:01 AM   #1
1978Mustang
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Default Sony KDL-40s4100 No Picture/Sound/Backlight

Hi Guys:

I just acquired a used Sony KDL-40s4100 LCD TV with no picture, sound or backlight. The power light IS on and can be controlled with the remote.

I've checked all the voltages from the G (power supply) board and they are all OK. From what I've researched, everything points to the A (Main) board, but I have one question. Wouldn't the backlight (inverter) come on even if the A board was faulty, or does it control the backlight as well?

I've even gone to point of checking all the regulators on the A board, and
they all show what they are suppose to show (1.2v, 1.8v, etc). Of course the A board is the most expensive to replace, so I just want to make sure before
I replace it.

Is there any way to get the backlight inverter to turn on manually?

Thanks!
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Old 10-13-2010, 10:17 AM   #2
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Please post some pictures of the boards in question so we can give you ideas of what to check next. Make sure that you use the "Manage Attatchments" on the posting page.
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Old 10-13-2010, 10:46 AM   #3
1978Mustang
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

This is weird, and I have no way of explaining it! Looking through the schematic, I found CN2502 on the A board, and it contained most of the back light signals. I unplugged it and the back light came on. Of course, I checked for video and of course there was nothing.

I power cycled the TV with the connector back on, and low and behold, the tv powered up with picture and sound

I'm so confused
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Old 10-13-2010, 12:16 PM   #4
1978Mustang
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Just as an update:

I reassembled the TV, attached an antenna and powered it up. Perfect picture and sound! Was it a bad cable? I don't know as I couldn't get it to quit again. It's been on for about an hour and a half with no issues.

Being a technician, I worry about repairs that I don't know what fixed it I think I'll use it as a shop TV for a few weeks before giving it to my son.....
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Old 10-13-2010, 12:30 PM   #5
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

I hear ya. As you know, it may just have been re-seating a connector. Well done, lol. If there is anything else, it will happen agian. But for now, enjoy.
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Old 10-13-2010, 01:08 PM   #6
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Rule # 1. A problem that goes away by itself will come back by itself.

$.02 diagnosis. Bad solder joint, either on the connector or on one of the nearby ICs. When you unplugged the connector the board flexed slightly, the two surfaces rubbed together, and broke through the oxide that was preventing contact.

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Old 10-19-2010, 09:49 AM   #7
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Since *repairing* the TV, one problem has raised it's head. Now, whenever the TV is switched off, the TV forgets all it's channel information. I would think that info is stored in RAM? If so, I wonder if both problems were related?

Isn't this fun

Thanks for the input guys....
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Old 11-01-2010, 10:59 AM   #8
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

I had a sanyo and reseated all the connectors and it's still working after a year. For the channel memory problem, check to make sure the stby power is correct.
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Old 09-22-2011, 06:53 PM   #9
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

I have the same problem with my Sony KDL- 40s4100. There is no picture, sound, or backlight. So I have decided to try your solution to your problem by disconnecting CN2502 on the A board. When i unplugged it the backlight came on,I was glad. Then I plugged the connector back on and power cycled the tv. Sadly the tv didnt power up with picture and sound like yours. So does this mean that the A board is damaged?
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Old 09-22-2011, 08:56 PM   #10
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

I have the same problem with a sony kdl-46s4100 and change the A-board and the t-con board and no solution, the tv is with no picture and no sound.
The power supply have voltage 3.3v, 6.5v, 15v. only the 12v is in 11.7v. I don't know were is the problem.
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Old 09-23-2011, 12:47 AM   #11
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Quote:
Originally Posted by 1978Mustang View Post
Since *repairing* the TV, one problem has raised it's head. Now, whenever the TV is switched off, the TV forgets all it's channel information. I would think that info is stored in RAM? If so, I wonder if both problems were related?

Isn't this fun

Thanks for the input guys....
Had this problem with a Samsung I repaired, it would forget all picture settings i.e. brightness if power goes. The fix was to go into the plug and play install, and when it asks if you want it in shop mode or home mode, put it in home mode.
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Old 03-21-2012, 11:40 PM   #12
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Hi! Having the same problem, but trick with that connector did not resurrect my TV. Was anybody able to fix it by replacing A board? Thanks!
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Old 03-22-2012, 08:58 AM   #13
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Here are the service manuals:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

Are you getting any blinking error light?
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Old 05-14-2012, 09:37 PM   #14
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Suddenly, my KDL-40S4100 developed the same problem. It was working fine one day, and not the next. No picture, no sound, no backlight - just the green power LED.

I checked for loose connections and found one or two, but the problem persists. I removed CN2502 and powered up. The backlight came on and the panel cycled green, blue, red, stripes. I powered down and reconnected CN2502, but the problem persists.

I have also checked for loose ground screws.

This is my first time trying to fix a TV, so any advice would be greatly appreciated.
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Old 06-02-2012, 05:32 PM   #15
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Smile Re: Sony KDL-40s4100 No Picture/Sound/Backlight

I alos came across one of those Sony tv and have also the same issues, no pictures, so sound and no backlight.

powering the tv up, the Green led is lit and steady.

i have taken the tv apart and took the power supply out and put it back in and reconnect all the harnesses and the problem was still there.

took my voltmeter and took some voltage around the T301 area. at the output? 0V. at the input? over 70 Volt
Could it a bad Relay?

CN501 also had no power
Cn503 have all the power and proper signal

i don't think the T-con is the issue as i am looking more towards a bad power supply unless i am wrong.

any feedback or ideas will be greatly appreciated.

Thank you
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Old 06-03-2012, 03:31 AM   #16
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Based on your description we know the main fuse is ok and that is about all.

We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
http://www.badcaps.net/forum/attachm...1&d=1290283049

http://www.badcaps.net/forum/attachm...7&d=1280167246

It will be useful if you can say a bit about yourself - skills tools etc.
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Old 06-03-2012, 11:10 AM   #17
aquaangel
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Smile Re: Sony KDL-40s4100 No Picture/Sound/Backlight

this is the Power supply off the tv



i don't have the botom side of it, but i did inspect all the welds and look good so far, no Extra flux laying on the board.

As for my experience:
well i graduated in Audio video repairs like over 13 years ago, so technology sort of got over me, but i still grasp the concept on how they work as i usually try to keep myself up to date with new machines.

i do have the basic tools for repair like the soldering iron, flux and etc. i usually buy new equipment whenever i need them to complete the job.

Been rebuilding Xbox, Xbox 360, Ps3 and Apple computers for quite some time as i can repair them with my eyes closed now.
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Old 06-03-2012, 01:28 PM   #18
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Picture is not really sharp enough for trouble shooting - I also asked that you did not post inline or host offsite and you have managed to do both. I asked this as some of our members wont look at threads with pictures posted like that.
You need to give us more detail about what you are doing - we dont know
CN1 from CN3 Please retest and post as follows
CN1
Pin 1 12v actual 12.1v
Pin 2 5v actual 4.2v
and so on for each connector. Use a corner ground screw near the connectors for the black probe.

On the primary side there are 3 small capacitors can you say what values they have and the board numbers - One will be a startup cap perhaps 47uf or 68uf 50v.

Please can you also post a picture of the main board and try for a sharper pic of the
PS so we can see the board numbers.

Last edited by selldoor; 06-03-2012 at 01:30 PM..
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Old 06-03-2012, 02:18 PM   #19
aquaangel
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

Will do my best to post a clearer picture as i took it with my iphone and will do more testing with voltage readings and will also try to post the pic here instead of my facebook account.



Quote:
Originally Posted by selldoor View Post
Picture is not really sharp enough for trouble shooting - I also asked that you did not post inline or host offsite and you have managed to do both. I asked this as some of our members wont look at threads with pictures posted like that.
You need to give us more detail about what you are doing - we dont know
CN1 from CN3 Please retest and post as follows
CN1
Pin 1 12v actual 12.1v
Pin 2 5v actual 4.2v
and so on for each connector. Use a corner ground screw near the connectors for the black probe.

On the primary side there are 3 small capacitors can you say what values they have and the board numbers - One will be a startup cap perhaps 47uf or 68uf 50v.

Please can you also post a picture of the main board and try for a sharper pic of the
PS so we can see the board numbers.
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Old 06-03-2012, 03:06 PM   #20
aquaangel
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Default Re: Sony KDL-40s4100 No Picture/Sound/Backlight

k here it goes
on the primary side

There are 2 capacitors of the same size at 100uf at 50Volt, locations
C609-C909

there is also a smaller one at 22uf at 50Volt location c905
all of them from the Primary area.

As of CN1 is the main power source reading more or less 114-120 volt ac.
Cn3 not found and couldn't found even in the schematic manual that you guys provided as a PDF file for that model.

Here are some clearer pic directly to this site

Now some reading at Cn503
pin 1 "12V" reading 11.5 V
pin 6 "n/a" reading 10.2
pin 7 "n/a" reading 10.2

cn301:
pin 1 "15V" reading 15.6v
pin 5 "6.5v" reading 7.1
pin 7 "3.3v" Reading 3.3v
pin 8 "3.3v" Reading 3.3v
pin 9 "3.3v" Reading 3.3v
pin 13 "12v" reading 11.5

Cn302
pin 3 "3.3v" reading 3.2v
pin 4 "3.3v" reading 3.2v

CN303
pin 4 "n/a" reading 3.3v

Now also found something weird. i disconnected cn 303 and the backlight is flickering like a strobe light. If i reconnect it? i am back to black.

All readings were done with the unit Powered ON, not on stand by
Attached Images
File Type: jpg DSCN4289.JPG (93.6 KB, 43 views)
File Type: jpg DSCN4295.JPG (110.3 KB, 35 views)
File Type: jpg DSCN4287.jpg (387.8 KB, 46 views)

Last edited by aquaangel; 06-03-2012 at 03:57 PM..
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