Samsung LED TV driving me crazy

[Rossputin]

Hello all,

We had an electrical storm which damaged some equipment including Samsung UN46C8000.

I bought replacement (used) power board.

TV would just click (soft click, short pause, loud click, long pause, repeat) at what I assume is a relay on the power board.

I then bought a new (used) main board.

TV worked for 5 minutes, then returned to the behavior described above.

At one point, I think disconnecting ribbon cable to T-CON made the clicking stop (but obviously the TV didn't otherwise work). Now, disconnecting that cable has no effect.

Disconnecting larger connector between power and main does stop clicking. (Labeled CNM801 on power board.)

I was wondering if anyone with some experience with this stuff has any thoughts on what the most likely problem is.

I have replaced 2 of the three boards, but the replacements were used boards.

I'm reasonably certain the main board was good when it arrived. Not sure if something else has now caused it to fail since it worked for 5 minutes.

I've been trying to fix this for two months and it's driving me nuts!

Two small fuses on TCON test good (not more than 1 ohm resistance).

Any help much appreciated!!!

[Ltank]

Re: Samsung LED TV driving me crazy

I have one in the shop now. I am not able to find a Service Manual for it. It is dead. I bought a New P.S. and it still did not work. I tried to force the PS on by connecting the A side 5vdc
to PS_On pin and the B side 5vdc cycled on/off. Did you measure any voltages? Were they as labeled near the connectors? I think I had a bad New P.S. No tech info is a drag. No freestuff out there for this model.

[Rossputin]

Re: Samsung LED TV driving me crazy

I really don't know where to measure voltages...but it sounds like this clicking power supply is a fairly common problem. it's just weird that I got a bad power supply to replace a bad power supply.

[Ltank]

Re: Samsung LED TV driving me crazy

There is a cable from the main board to the P.S. that is labeled. Put your Dvm black lead to chassis metal ground and the read positive lead to the labeled connector. Put meter on dcv

[Rossputin]

Re: Samsung LED TV driving me crazy

I should add that there is a small button on the main board and that after the first short quieter click, if I push that button, it makes the loud click happen immediately, and then the cycle continues.

[Rossputin]

Re: Samsung LED TV driving me crazy

There is a cable from the main board to the P.S. that is labeled. Put your Dvm black lead to chassis metal ground and the read positive lead to the labeled connector. Put meter on dcv

I'll check it...there are two cables from main to p.s. I'll look for 5v label.

Is it possible for boards to short to chassis???

[Rossputin]

Re: Samsung LED TV driving me crazy

OK, now this is really crazy but makes me think that I might not be too far from a solution, if any of you electronics experts can help me:

The larger of the two connectors between the power supply and the main board appears to have two rows of 9 pins each.

When I test the voltage between ANY of the accessible pins that come off the power board and into the bottom of the connector, with pos lead on pin and neg lead on chassis of TV, the TV turns on!!!!

I hope I'm describing this well enough...let me elaborate just in case:

There are 9 metal pins which come out of the power board, then bend at a right angle to go into the bottom of the connector which is labeled CNM801 and CNM802 (I think one label for each row of pins).

If I test the voltage between any of those pins as they come out of the power board (with positive lead) and chassis (with negative lead) the TV turns on. TV is not connected to any input but the "check signal" message comes on the TV as does the little box in upper left corner saying what input the TV is set to.

I took out the cable between ps and main and checked every connection with ohm meter, and the cable is fine.

I'm not nearly expert enough in electronics to figure this out...grateful for any help! I have a feeling I might be one weird ground connection away from a fix!!!

[Rossputin]

Re: Samsung LED TV driving me crazy

(This was an error...deleted)

[Rossputin]

Re: Samsung LED TV driving me crazy

I just tried same voltage test on pins on main board and they do not see the voltage, nor does TV turn on, even though cable shows 0 resistance between two ends of the cable.

In other words checking voltage at pin on power board will turn on TV but checking voltage at pin on main board which is connected to same pin on power board will not turn on TV.

What does this mean??? Help!!!

[Rossputin]

Re: Samsung LED TV driving me crazy

And I've also just discovered that I can make the TV turn on by simply touching one of my meter's test leads to any pin on the connector on the power supply side but it makes no difference if I touch the same lead to the pin on the main board that's connected to that power board pin! I don't even have to have the other lead touching the chassis to make the TV turn on!

Is this starting to sound like a bad power board, or a bad ground somewhere???

Any advice on what to check now would be much appreciated!

[selldoor]

Re: Samsung LED TV driving me crazy

Without pictures it is very difficult for us to guess what is going on- even with a good description. If it works when you touch a pin with your probe have you tried just pressing on the connector with a non conductive rod.

As you say may be a bad ground - slacken and retighten all the board screws and remove and replace all connectors.

[Rossputin]

Re: Samsung LED TV driving me crazy

Wow, you are a genius!

I pushed on the connector with a pencil eraser and the TV came on. And then I pushed on the edge of the board near the connector and the TV came on.

Amazing.

So, does this imply a loose connection between board and connector? Should I remove board and look at the back side of it?

The more specific the instructions, the better for this relative novice... I'm reasonably comfortable doing my own soldering if that becomes necessary.

[selldoor]

Re: Samsung LED TV driving me crazy

It may be just the pins are not connecting inside the socket or a wire not connecting to a pin. or a pin not soldered to the board.
If you can try and establish which pin is not connecting properly.
Examine the pin and socket with a magnifying glass to see if the problem is visible.
Try pulling on just that wire - see if it pulls out.
Take the board off and examine the back to see if you can see if the pin is unsoldered.

If it has it may be difficult to solder due to the proximity of other pins but you can try.

[Rossputin]

Re: Samsung LED TV driving me crazy

I can only easily access half the pins, because the other half are concealed under the connector.

the half that I can access are working in the sense that there is zero resistance between the pins on the ps board and the matching pins on the main board. but that's just half of the pins, and it still doesn't prove that the connector on the ps board is actually connected to the board.

in fact, since giving it a little push makes the TV come on, I'm thinking that there's a bad connection between the ps board and the connector on the board.

i've tested the continuity of the connector cable and it's good on all 18 pins, i.e. taking out cable and measuring about 0 ohms in each of the 18 runs.

Does that make sense?

I'm thinking I need to take the board off and look at the back of it.

But I have a 5-yr old son and we're about to head out to one of his friend's birthday parties right now! So I'll try in a few hours.

[truep]

Re: Samsung LED TV driving me crazy

I've had a couple of sets with bad solder joints on the connectors. Try re-soldering all the pins on the connector. I usually use the solder sucker (after applying a little lead-tin solder) to remove the crappy no lead solder and re-solder all the connections. Sometimes just heating and melting the existing solder will work. You can get to the other pins from the back of the board.

[Rossputin]

Re: Samsung LED TV driving me crazy

I'll give it a try...need to make sure I have small enough tip for soldering iron and make sure I don't end up shorting stuff out!!!

[Glitcher]

Re: Samsung LED TV driving me crazy

From reading the first post, it does sound like a cold solder joint somewhere since the tv will turn on intermittently. I had a tv before where if I tested one of the pins on the PSU while relative to ground, the turn would turn on. Turned out to be a bad solder joint on a grounding pin i think

[Rossputin]

Re: Samsung LED TV driving me crazy

One of the pins on the connector on the back of the board has no solder on it.

I tried to solder it myself, but I could not get the solder to stick to the pin or run down the pin to the board, and I'm afraid to mess it up so I'm going to take it to a local tech repair guy who's reasonably priced.

[truep]

Re: Samsung LED TV driving me crazy

What kind of solder are you using? You need 60/40 rosin core for this.

[Rossputin]

Re: Samsung LED TV driving me crazy

It just says rosin core.

But it's in such a tight spot that I almost messed up the solder on the next pin, so I'm just going to take it to a guy I know who will take care of it for no more than $20, and maybe less!

Isn't it funny how long it can take, and how many headaches, to find such a small problem?