LE37R88BD Backlight Turns Off After 2 - 3 Seconds

[Easky15]

Hi all, I have here a Samsung le37r88bd tv and when turned on its fine but 2 or 3 seconds later the backlight goes off, I still get sound and can see the image using a torch, I replaced 2 bulged 1000uf 35v caps on the power board and also tried a new inverter board but neither helped, Would anyone know what else might cause this fault?? All voltages from the power board are as they should be when the set is on so i dont think its that.....

[vinceroger69]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

do any of the voltages drop out on the psu when this happens after the one or two seconds whilst its working?

[ivoh]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

like he said check the voltages, also make sure that the inverters signal to turn on is not disappearing. you might also have a fault or protect pin, measure that too if you have one.

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

All voltages remain constant when the backlight is on and when its off, Also when it's off the inverter is still receiving the 5v power on signal and the 24v supply, The main board is a BN41-00813B and i tested a BN41-00813E in it, only thing different was the t-con lvds cable connection, again i got the same fault with the backlight, went out after 2 seconds so i think its not the main board,

[budm]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

How about the dim signa (see if it use PWM for dimming or Analog dimming)l? Also is there a cable between the T-CON and the inverter board?

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

Sorry still learning budm.. ;-) How do i test the dim signal and how do i check if it's PWM or analog dimming??

[budm]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

Let me see the pictures of connector so I can see the labels. Pictures of the whole back side of the TV and the whole boards.

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

Hope these help...

http://tinypic.com/r/9zwn7s/8
http://tinypic.com/r/fx3tj5/8
http://tinypic.com/r/favu6d/8
http://tinypic.com/r/11w356p/8
http://tinypic.com/r/334uf0z/8
http://tinypic.com/r/1znbsbs/8

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

???

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

Would anyone have anymore ideas what could be wrong with this set??

[budm]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

OK, here is the SCH provided by TOM.
Check the DC voltage on CNM804 BL_ON, ADIM, PWM, 24DET. Also check the 24VDC PIN.

[bammbammfran]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

FIRST : Please post your pictures on this site instead of a site that shoves ads down your throat !!

Your inverter board is probably having issues. one of the seven transformers may be bad or a transistor on it may have gone.
Pictures of that board with the cover off of it would help

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

FIRST : Please post your pictures on this site instead of a site that shoves ads down your throat !!

Your inverter board is probably having issues. one of the seven transformers may be bad or a transistor on it may have gone.
Pictures of that board with the cover off of it would help

Was not able to upload here due to crappy file size restrictions so thought it was easier just to upload it there rather than piss about reducing the resolution, Also if you read my first post i have already bought another inverter from ebay and it does the exact same thing, (whats the chance both have the exact same fault) prety unlikely i think so the only board i think it can be is the power board,

[Easky15]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

OK, here is the SCH provided by TOM.
Check the DC voltage on CNM804 BL_ON, ADIM, PWM, 24DET. Also check the 24VDC PIN.

Thanks BUDM, trying this now

[bammbammfran]

Re: LE37R88BD Backlight Turns Off After 2 - 3 Seconds

I missed where you said you tried a different inverter.
It is possible that they do have common issues especially with those style transformers, but I do not know for sure.

What you can do is try to see if one bulb might be totally cooked by trying to turn it on with one bulb plugged in at a time
Changing your desktop background to all white may help you see each bulbs brightness a little better

if for some reason one does not light or looks really dark, loosen the inverter so that you can slide the board a little and try that same bulb in another transformer plug and/or another bulb into the transformer that showed dark

this can sometimes show an issue if a transformer or bulb is really bad