Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

[timleferink]

Hello to everyone here!

I've learnt a lot while searching this forum for a few devices before, but unfortunately I've now got a problem I really can't find any info on.

Recently, I got a Samsung UE40D6530 that has an interesting issue:

After being turned off for an hour or so, it turns on, displays a picture properly for between 5-20 minutes. Then the picture becomes distorted, starts flickering, turns to black and then the infamous relay clicking starts. Power cycling the device leads to more black screen and relay clicking.

To clarify: see here: Youtube video

I've checked the voltages from the power supply and they all seem good and stable (checked with a proper oscilloscope). This seems to make sense considering how long the TV continuous functioning. The caps don't look buldged or anything.

As the picture becomes distorted before the real problem starts, I suspect either the mainboard or the TCon board. Disconnecting the TCon board does not stop the relay switching on and off.

Can I now assume that the problem lies in the mainboard?

If so, are there some pointers to what voltages/caps etc to check?

For reference I included a picture of the Mainboard (BN94-05035G) and the PSU (BN44-00427A).
(note the black spot on the PSU was from when I connected my ground clip to this pin, apparently it's not floating as I expected :P . My 6A breaker blew, all fuses stayed intact and the functionality of the device was not affected).

I'm afraid that because it works for multiple minutes, and then not for an hour, it might be heat related, and off course the main processing chips get the most hot.

Also, I'm not afraid of soldering SMD components, but reballing a CPU/DSP is a stretch. If all else fails I'm willing to give it a try though .

Thanks in advance,

Tim Leferink

[zomi]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Disconnect mainboard
and see if backlights come on and stay on

[timleferink]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Disconnect mainboard
and see if backlights come on and stay on

Forgot to mention this, sorry! The backlight turns on and stays on.

[sordids999]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

I think I've seen this before in a previous post where the legend connections at the power supply and is suspect but I may be wrong but check each wire connection
Also what's the black area around the bridge rectifier ?

[freakaftr8]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

This is similar to the problem that the A series had with a bad C102. It's probably a dad capacitor somewhere on the main board that runs nvram. I would take a can of freeze spray in start hitting the board in various areas when it develops the problem and see if the TV comes right back on.

[timleferink]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

I think I've seen this before in a previous post where the legend connections at the power supply and is suspect but I may be wrong but check each wire connection
Also what's the black area around the bridge rectifier ?

I'll do a double check, though the device seems very clean (no dust etc), I've also reconnected all cables.
The black area is where I mentioned I connected my ground probe on my oscilloscope .

This is similar to the problem that the A series had with a bad C102. It's probably a dad capacitor somewhere on the main board that runs nvram. I would take a can of freeze spray in start hitting the board in various areas when it develops the problem and see if the TV comes right back on.

Thanks for the info! I've ordered some freeze spray and will try this tomorrow, I'll keep you posted.

[timleferink]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Got the freeze spray in today. After some testing the tv indeed turns on again!

After a while we found that the problem seems to arise in the spot attached below, or at least in close proximity. A little spray: backlight, then it turns off after a few seconds (up to 10s). Checked all the caps closeby, but no shorts.

To make sure it wasn't a bad connection I resolderded the crystal, caps and resistor. After this the tv turned on for 30 minutes, weird!

Then the audio stopped intermittently, then in its entirety, fuzzy image, clicking relay. I didn't have the speaker on before, so this might shed a clue for someone.

Sprayed some more freeze spray, image. I touch the crystal, tv turns off instantly!

Could the crystal be faulty?? Or should I look at the caps that run the crystal?

Thanks!

Tim

[freakaftr8]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

When you freeze the crystal if it goes out of frequency it's coming back into frequency or somewhere close. I would say either a bag crystal or some resistance change within the crystal. Swap it out 1st get the specs on the top of the cap of the crystal.

Looks to be a 24.000MHZ

[timleferink]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Got a new 24MHz crystal in today, and indeed, everything works!

Thanks to everyone for helping out! The freeze spray tip was new to me, this is great when you can't easily take the board out and use alcohol, and also, in this case it probably wouldn't have worked.

Soldering the crystal with a regular soldering iron was a bit difficult as shown in the picture, should have used my hot air gun (would have saved the pads under the crystal... ).

Tim

[nomoresonys]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Well done Freakaftr8, you named that tune (solved the case) in 2 posts.

[freakaftr8]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

Good to hear!

[Andrew F. Ali]

Re: Samsung UE40D6530, fuzzy image after a few minutes, then relay switching

good to hear!

+1000