Buttons not working on Samsung LE37S71B

[Dannyx]

Good day folks. I've got this Samsung TV with a seemingly trivial yet slightly annoying issue: the buttons on the side don't respond AT ALL, not ever erratically like it usually happens when buttons on TVs go bad. Interestingly, I thought the TV was dead when I first got it, because it didn't come with a remote, so I naturally tried the buttons first, which of course got me nowhere. Then just out of curiosity, I grabbed a Sammy remote and the thing fired up perfectly.
Initially I thought the microswitches were busted, so I replaced one of them just to check but it didn't change anything. Looking at the service manual on page 122 we have the FUNCTION block (see below), but the only thing to check there would be the A5V voltage which appears to be OK (slightly lower than I'd like it, at only 4.8v from what I recall, but considering the remote works, I assume the power section for the buttons is running fine. Doubt it's a software issue, like something becoming corrupt, though I'm not eliminating that theory entirely just yet. Has anyone ever dealt with unresponsive side keys on Sammies before ? If so, what could be the issue, besides the microswitches ? Cheers.

[vinceroger69]

Re: Buttons not working on Samsung LE37S71B

tv stuck in hotel mode?
With the TV switched on press MUTE - 1 - 1 - 9 - ENTER this takes you direct to hotel mode i think

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

tv stuck in hotel mode?
With the TV switched on press MUTE - 1 - 1 - 9 - ENTER this takes you direct to hotel mode i think

I've already accessed the service menu and hotel mode appears to be off, albeit I went INFO-MENU-MUTE-POWER, so maybe that takes me to a different menu. I'll try your method as well

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

tv stuck in hotel mode?
With the TV switched on press MUTE - 1 - 1 - 9 - ENTER this takes you direct to hotel mode i think

I tried that, but it doesn't seem to do anything, despite reading somewhere else that that IS indeed the code for accessing hotel mode.

[dick_barton]

Re: Buttons not working on Samsung LE37S71B

I once picked up a set where the side button panel ribbon cable had become detached from the IR board. Possibly someone had already tried to repair the set and didn't put it back into place.
Have you checked that the cable has not been damaged. Perhaps one of the screws cutting through it.

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

I once picked up a set where the side button panel ribbon cable had become detached from the IR board. Possibly someone had already tried to repair the set and didn't put it back into place.
Have you checked that the cable has not been damaged. Perhaps one of the screws cutting through it.

Forgot to mention that I DID open up the TV but nothing looks out of the ordinary, at least not visibly. Highly unlikely a cable got busted, because the side buttons and IR are connected to the large power button in the middle, which THEN goes to the main board, so considering the remote works, I doubt something's wrong with the connections.

[culcuhain]

Re: Buttons not working on Samsung LE37S71B

You might have a stuck button. I picked up a TV where the volume was maxed due to a stuck button. No other buttons would work. Using the remote you have increase the volume and see if it drops on its own. Decrease the volume and see if it increases on its own. Check each microswitch. You IR board where it goes to the main maybe labeled. Check the voltages for each button there.

[vinceroger69]

Re: Buttons not working on Samsung LE37S71B

eeprom re set like on the older samsungs where you short two pins and the tv re writes the data back Not sure if it will work on this model or sort the issue out though

[dskall]

Re: Buttons not working on Samsung LE37S71B

You have several key inputs. Do they change voltages when you push buttons?

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

eeprom re set like on the older samsungs where you short two pins and the tv re writes the data back Not sure if it will work on this model or sort the issue out though

No need to "improvise" like that, as I have an EEPROM programmer, so I can take the chip off, read it, back it up and THEN wipe it. I did find a bulged cap on the 5Vsb bus and although the TV worked OK, I read somewhere while working on another TV, that bad filtering can lead to corruption of EEPROMs. Don't know if it's the case here though...

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

You have several key inputs. Do they change voltages when you push buttons?

Yes they do: I get various readings in the range of 1-3v, all of which drop to 0 or thereabouts when I press the keys, so I'd say the keys function normally - it's the main board that's busted. Resetting it via the service menu didn't help. I might try pulling the EEPROM out and wiping it, provided I have the required patience, since it's a "test" TV and doesn't actually require fixing

[maxvalutech]

Re: Buttons not working on Samsung LE37S71B

In the small number of voltage checks I have done with control buttons the only one to go to zero was off which went from 3.3v to zero - others changed voltage within a small varied range. ???

[attainteddragon]

Re: Buttons not working on Samsung LE37S71B

each input has a different voltage so that the microprocessor can understand the input value. resistive ladder array. so that isn't right.

[Dannyx]

Re: Buttons not working on Samsung LE37S71B

each input has a different voltage so that the microprocessor can understand the input value. resistive ladder array. so that isn't right.

I must admit I haven't been too thorough in checking, mainly because the schematic was not too easy to interpret...might dig into it further.

[maxvalutech]

Re: Buttons not working on Samsung LE37S71B

[QUOTE=attainteddragon;754045]each input has a different voltage so that the microprocessor can understand the input value. resistive ladder array. so that isn't right.[/QUOTE)

That's what I'm getting at on the set I just checked again input voltage to buttons pcb is 3.3 and as a button is pressed that voltages drops by a varied amount to say 2.08. 1.65. 0.86. etc. The poster says all his go down to zero so to me seems like button pcb could be shorting.

[attainteddragon]

Re: Buttons not working on Samsung LE37S71B

some of these button pcb's have ceramic caps that fail and drag the voltage down.

that is where i would be looking first.