samsung lcd, new inverter board, has sound but no picture

[dbook07]

The original problem with my TV was that it would occasionally power itself off. To get it to power on again I would have to unplug it first. The TV is only 4 years old. It thought this might cause a problem in the long run so I decided to order a new (refurbished) PSU/Inverter board - it's a model where both PSU & Inverter are on the same board.

Had no luck with the new board as the TV now has a new symptom. Picture would come on for only 1 second, then it will go off but sound remains on. I thought there might be a problem with this new inverter board so I returned it. I plugged the original board back in, TV works fine, although now I'm back to the old problem with the TV occasionally switching itself off.

The store has now sent me another board to try out - but again I get picture for 1 second then only sound remains on. Surely this board can't be another faulty board? The fact that my original board gives me picture makes me believe the fault might have actually been with the T-CON board? Would this be consitent with the story so far and should I go ahead and order a new T-Con board? Last thing I want to do is start replacing all the boards and ended up having to buy a new TV anyways!

Thanks a lot for your help in advance.

[budm]

Re: samsung lcd, new inverter board, has sound but no picture

When you say you do not get pictures, can you still see the backlights staying on? If backlights are on but no pictures, then next place to look will be the main board and the T-CON board.

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Thank you for your reply budm.

I believe the backlight is on - faint picture when shining a torch at the screen.

Does this mean there is no problem with my new PSU/Inverter board? How does this explain the fact that I still get picture with my original PSU/Inverter board?

Seems like a similar problem to this guy: https://www.badcaps.net/forum/showthread.php?t=30654 although my model is Samsung LE40B650, and he fixed it by replacing the T-CON board. Are you suggesting I should look to replace the mainboard before the T-CON board?

[budm]

Re: samsung lcd, new inverter board, has sound but no picture

So you can see screen glowing if you look at it in he dark room? If that is the case I do not understand about fainted pictures when shining the flash light on the screen if the backlights are working, the power supply-inverter combo board is for supplying high voltage for the CCFL backlights, and low voltages to run the main board.

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

the screen is pitch dark in a dark room - no glowing. i can only see fainted pictures when shining flash light onto the screen.

[budm]

Re: samsung lcd, new inverter board, has sound but no picture

If that is the case, the backlights are not on. Post good clear pictures of your power board so we can look for BL_ON (INV_ON) pin to check to see if the signal is present or not.

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Split them into four images, hope quality is clear enough

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

DMM set to DC, counting down from the top left of the black connector C801, 4th pin down on left(red probe).... black probe to chassis.... watch the reading when turning the set on. Post results

[budm]

Re: samsung lcd, new inverter board, has sound but no picture

Here is the diagram from TOM66 website

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Thanks guys for the replies. I'm a newbie at this hence I decided to replace an entire board rather than inspect individual components. Now I wish I had found this forum before forking out on a new, possibly faulty board!

Will have to go out & purchase a multimeter tomorrow and post back results. Thanks again.

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

I'm getting around 4.0 on the 200m scale, when turning tv on. What's next?

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

Set your meter to 20 V dc.. follow my instructions in post 8.

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

I'm getting around 4.0 on the 200m scale, when turning tv on. What's next?

Wrong setting.

Look for V with a symbol that is a line with a dotted line underneath

This means Volts DC

V~ is Volts AC

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Thanks for bearing with me newtothis. I've switched the tv on, turn the multimeter to 20v, even got a spark off some other pin accidentally, but I'm getting 0 on that 4th pin.

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

When u said black to chassis do you mean ground?

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

Yes, Chassis works as a ground

Do you have all the cables connected?

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Yes all the cable are connected, apart from the socket I'm meant to be measuring from. I'm getting a spark on a different pin but I got nothing on this pin.

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

Plug it back in then test it by putting the probe into the top at the pin you are testing... make sure set is off at this point... once ready watch the meter and turn the set on. post back results of what you see

[dbook07]

Re: samsung lcd, new inverter board, has sound but no picture

Sorry what I meant is that the power board is already connected to the power supply, but I've taken the cable (which connects this board to the main board) off off this socket in order to access the pin. Is this the correct settings, should I be expecting a reading, I'm not getting anything on any of the pins, only some sparks.

[newtothis]

Re: samsung lcd, new inverter board, has sound but no picture

You need to plug all the connectors back in... just push the red probe into the top of the connector at the location the pin is... so just where the wire goes into the connector.

The mainboard sends the signal to the Power Supply to turn on, so without the mainboard plugged in the PSU wont start up hence we cannot see if you have a voltage or not