TV back light repair help Philips 50put6400/12

phillyd1981

Well-known Member
I've got a Philips 50put6400/12 TV with a black screen and I think the issue is with the backlight.
If I turn the TV on after leaving it plugged in for 5 mins I get the logo display for 2 seconds then the back light goes out.
If I plug the TV straight in then power on I get just a black screen with the backlight not coming on at all.
If I shine a torch on the screen I can just about see a image and use the menus.
Looking at the power board that the led panel cables plug into I can not see any blown capicators or any visible damage.

Does anyone have any advice on anything I could check or test.

Thanks.
 
Last edited:

phillyd1981

Well-known Member
Power board photos
IMG_20210122_131156.jpg
IMG_20210122_131216.jpg
IMG_20210122_131202.jpg
IMG_20210122_131105.jpg
IMG_20210122_131100.jpg
IMG_20210122_131220.jpg
IMG_20210122_131116.jpg
IMG_20210122_131125.jpg
IMG_20210122_131120.jpg
IMG_20210122_131136.jpg
IMG_20210122_131128.jpg
 

aVdub

Distinguished Member
Had a similar issue with a Sony that turned out to be dry joints.

I'm no expert on TV repair but may be worth adding that to a search online.
 

brunation

Well-known Member
IIRC from monitors:

PS-ON should be low in standby and high when you come out.

I would expect BL_OFF/ON to go high then too.
If I turn the TV on after leaving it plugged in for 5 mins I get the logo display for 2 seconds then the back light goes out.
So your happy the back light works?

If I plug the TV straight in then power on I get just a black screen with the backlight not coming on at all.

So everything else functional.

So if you faked PS_ON then BL_OFF/ON should remain high.

BL_OFF/ON acting as a switch?
So what voltage after 5min+switch on +_5v or +12v ???

Something on the video PCB on the right might be signalling it off.

Edit:

Trace ... trace ... trace
 

phillyd1981

Well-known Member
Thanks. The back light is not faulty to my knowledge and I can see and use the menus if I shine a torch under the screen.
I will have to look at the BL_Of tonight.
 

maxwell

Distinguished Member
Had similar on a Samsung was a dry joint on the power board and an easy repair just remove the power board, turn it over and go over all solder points with a soldering iron.
 

nvingo

Distinguished Member
Had a similar issue with a Sony that turned out to be dry joints.

I'm no expert on TV repair but may be worth adding that to a search online.

Had similar on a Samsung was a dry joint on the power board and an easy repair just remove the power board, turn it over and go over all solder points with a soldering iron.
Philips were reknowned for dry solder joints during the 1980s-1990s, when their TVs were manufactured Western Europe and UK.
Surprised it's still an issue now they're sourced from areas of cheaper labour - they've had years to fix it.
 

brunation

Well-known Member
Add Philips 50put6400 to the thread title.

Modelchassispanelmainpower
40put6400QM15.2E LATPT400UA-DJ1QS5N715G7030-M0H-000-005T WK.1516715G6677-P01-003-002S
50put6400QM15.2E LATPT500DK-QS1715G7030-M0G-000-005K715G6973-P02-002-002H
55put6400QM15.2E LATPT550J1-QVN03715G7030-M0G-000-005K WK:1504
715G6973-P01-002-002H

Schematics look to be available on Russian site.

@maxwell suggestion seems easiest route.
 

phillyd1981

Well-known Member
Add Philips 50put6400 to the thread title.

Modelchassispanelmainpower
40put6400QM15.2E LATPT400UA-DJ1QS5N715G7030-M0H-000-005T WK.1516715G6677-P01-003-002S
50put6400QM15.2E LATPT500DK-QS1715G7030-M0G-000-005K715G6973-P02-002-002H
55put6400QM15.2E LATPT550J1-QVN03715G7030-M0G-000-005K WK:1504715G6973-P01-002-002H

Schematics look to be available on Russian site.

@maxwell suggestion seems easiest route.
Thanks would you happen to have a link please to the site you mentioned.
Did not get around to looking at it last night kids had a late night.
 

brunation

Well-known Member
I don't read Russian which is why I didn't link.

bing '715G7030-M0G-000-005K WK:1504 ru'

7th link down for me.
 

phillyd1981

Well-known Member
@brunation BL_OUT is was giving out 3.5v then 4v when retested later on. the back light came on briefly when i was poking the multimeter around the solder join. I've not had anymore time to look further into it.
 

brunation

Well-known Member
When backlight on everything ok? No evidence of dimming?

Youtube stuff so far is people having actual LED failures.

Identifying backlight invertor board is going to help.

Test BL_ON with TV in standby too but having no idea what it should be doesn't help.
 

phillyd1981

Well-known Member
Update- I removed the front/screen panel to get at the LEDs and at boot up the 2 top rows light up only with the lower 4 showing no signs of life.
So I then tried the 4 dead strips in the upper 2 connectors and they all do light up and looking at the power board it is bowed with the heat over time.

Was all set to order a power board when I noticed that I stressed the display screen to much and it's ruined now.
Any how I did quite enjoy taking the TV apart and playing around with it.
 

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