Samsung LE27T51B volume increases or decreases automatically

[LuisV]

Hi guys.

I have a situation with a Samsung LE27T51B with a volume issue.

The volume increases automatically or sometimes it decreases.

If I disconnect the button module, it doesn't do that, but the IR receiver is in the same board so we have no control over the TV.

I've already tested with the multi-meter all the buttons, and they are in open state. Even when the TV is increasing the volume they are all in open state.

I've measured all resistors of the board and all seams to be OK. I couldn't measure the capacitors because I don't know his values.

I'm attaching some picture of the boards and issue.

Any clue?

Thank you in advance.

Best regards,
LuisV

[CapLeaker]

Re: Samsung LE27T51B volume increases or decreases automatically

Did you try covering the IR on the TV with black tape or something? Maybe take the IR off the board and plug the button board back in. Also you could swap a button, maybe the problem shifts? Or take the offending volume button out and retest. See what happens and report back.

[LuisV]

Re: Samsung LE27T51B volume increases or decreases automatically

Did you try covering the IR on the TV with black tape or something? Maybe take the IR off the board and plug the button board back in. Also you could swap a button, maybe the problem shifts? Or take the offending volume button out and retest. See what happens and report back.

Thank you CapLeaker for your reply!

Well, I've took out the batteries of the remote, so it couldn't be the remote. I forgot to mention, but I even desolder the 2 volume buttons and the issue persists.

I'll try to desolder the IR of the board and see what happens.

Best regards!

[nomoresonys]

Re: Samsung LE27T51B volume increases or decreases automatically

Could be sticky buttons, did you try cleaning them with ISA alcohol?

[CapLeaker]

Re: Samsung LE27T51B volume increases or decreases automatically

The problem does go away when the button board is unplugged, right? Maybe upload again some high resolution, straight shot pictures of the button board top and bottom. Maybe clean the whole board with 99% alcohol or acetone. Don't use the 70% stuff, as it leaves water after the alcohol evaporates. By any chance there isn't any brown glue on that board?

[R_J]

Re: Samsung LE27T51B volume increases or decreases automatically

The fault could be caused by one of the other buttons, there will be likely +(5) volts on one end of the resistor ladder and ground and then there is the line that goes to main with the selected voltage for the command. Once the voltage reaches the threshold of the command it activates (ie:2.0v vol-up, 2.5v vol-dn, menu 3v) If menu button becomes leaky and starts to conduct, the voltage will slowly rise and if it hits 2v when the key input line is read, the vol goes up if it is at 2.5v when the line is read, vol goes dn.

They sometimes use clock & data lines for the button commands but the same situation can happen