EEVblog #780 - Samsung LCD TV Dumpster Dive Teardown

[Ampere]

Another great video, Dave. I always learn something from your videos. Especially the ones where you repair or design something.

I do have a question. What is the freeze spray meant to do? How would cooling a component make it work (assuming it wasn't above its rated temperature beforehand)?

[AF6LJ]

Good video and good troubleshooting..

I am thinking bad conductors on the glass itself.
This TV could have been struck or have fallen over for all we know, damaging the on glass conductors.

[ultranalog]

Regarding the slow fading in of the bars: that looks like an analogue problem.

Remember this is a TV from 2009 or so. The 'PC' input is 100% a VGA input. Have you tried selecting the HDMI?

[N2IXK]

Cooling a component causes it to shrink and possibly deform enough to make/break a cracked solder connection.  Cooling a semiconductor junction can help spot leakage currents, noise, voltage offsets, etc.  that vary with temperature. 

In the case of BGAs, it can help find a cracked solder ball or poor joint under the package.

My next step on troubleshooting this beast would be to scope all the power supplies for noise (bad caps) and then try a reflow of the main PCB. I really don't think this is a panel issue.

Finding a used board on eBay is always an option. Have to decide if the monitor is worth the $80-$100 gamble, or find a seller who accepts returns. If you were able to troubleshoot the boards to component level, it would likely be one of the big custom ASICs anyway, which would be nearly impossible to get replacements for. 

[retrolefty]

Lots of guesses (too many really) on what the symptom cause might be, but to be honest I don't think it can be determined without using complete schematic(s), maintenance manual(s) and of course a good O-scope. The things tried (freezing chips, wiggling cable connectors, etc are only useful when not having the needed documentation, test equipment, and experience, and in that case it's as much luck as skill of being able to determine root problem.

 Still the tear down was very entertaining in seeing what all is included in a large LCD TV, pretty impressive tech on even this somewhat 'older' TV. I wonder now that prices have come down so much on this size what 'cost factor' changes have been made in more recent TVs?  It sure is a large volume, low margin, consumer market. It's amazing how such a competitive market can keep giving us more and more for less and less. NASA could not design and build the same product to the same price point. 
 

[Ampere]

Cooling a component causes it to shrink and possibly deform enough to make/break a cracked solder connection.  Cooling a semiconductor junction can help spot leakage currents, noise, voltage offsets, etc.  that vary with temperature. 

In the case of BGAs, it can help find a cracked solder ball or poor joint under the package.

Thank you for the explanation. I get what you mean. It's a way to tell whether there's a fault in an IC or its connections.

I happen to have a bottle of duster spray so I might give this a try next time I'm trying to fix something.

[Stonent]

If you're going to toss out the TV anyway, I guess you have nothing to lose by baking one or more board that have BGA chips to get some of that cruddy lead free solder to reflow.
When I had a Tcon board issue with a Westinghouse TV the issue wouldn't show up until the TV had been on for a little bit.

[adcurtin]

If you don't get a remote and go to the service menus and stuff, you should at least put an external signal into the thing. You can much better control what's displayed and help narrow down the problem.

As others have said though, it makes a lot of sense for it to be a problem with one of the horizontal drivers.

[pickle9000]

Dave seems to get 100% working stuff or items destined for "silicon hell".

[sean0118]

I'm not sure if it has been mentioned, but could a failed crystal oscillator circuit cause this? I'm not sure how often it happens, but surely a crystal oscillator that has drifted out of spec would cause weird issues? 

[tom66]

This is a defective LCD panel. I have heard some people soldering very thin wires to pads on the drivers on the side of the screen to reconnect an internally failed connection. But usually it cannot be fixed without replacing the screen, making the TV scrap.

A temporary fix is to go into the service menu (TV in standby then press Mute 1 8 2 Power, or Info Menu Mute Power depending on the region) and adjust the "SUB BRIGHTNESS" or "SUB CONTRAST" figures, these can reduce the brightness to the point at which the pixels do not bleed.

Sadly this is extremely common with large screen (32" or above) Samsung LCD TVs and as such I can never recommend anyone buy one.

[Rasz]

This is a defective LCD panel. I have heard some people soldering very thin wires to pads on the drivers on the side of the screen to reconnect an internally failed connection.

I had a link somewhere to a .ro forum with a thread full of 'solutions' (pinout of tcon and tab test pads+what usually breaks for particular panels) for this very type of repair, sadly I cant seem to find it now

[G7PSK]

My pennies worth, try a hair dryer on the screen this sometimes either proves the fault with the lcd and on occasions even cures it and I have no idea why it does.

[Rasz]

This is a defective LCD panel. I have heard some people soldering very thin wires to pads on the drivers on the side of the screen to reconnect an internally failed connection.

I had a link somewhere to a .ro forum with a thread full of 'solutions' (pinout of tcon and tab test pads+what usually breaks for particular panels) for this very type of repair, sadly I cant seem to find it now

FOUND IT !
https://www.eevblog.com/forum/repair/panasonic-lcd-tv-images-are-sluggish-and-go-into-each-other/msg657801/#msg657801
http://monitor.net.ru/forum/topic375748-96.html

It would be epic if Dave managed to fix restoring individual tab connections, thats drunken russian level of hardware hacking right there.

[JoeMuc2013]

Hi Dave(s),

why don't you get your Flir E8 out and check if anything heats up beyond reason? The fact that the bars are fading in feels for me like something might be becoming red hot during the first few seconds after powerup.

Good luck anyway. This is very entertaining and makes up for a good troubleshooting guide.

Regards,
Joe

[PA0PBZ]

why don't you get your Flir E8 out and check if anything heats up beyond reason?

I think Dave already heated up enough stuff for now 

_{Hint: did you watch #782?}

[JoeMuc2013]

_{Hint: did you watch #782?}

Well, I did... after posting. Bummer! 

[qwertz]

Hi Dave,

I think I know what cause this issue, because I already repaired a tv with exactly the same problem.

The problem is located on the mainboard. There is a Samsung bga chip with some cracked solder balls. It is one of the two chips with a heatsink (the one which is closer to the t-con ribbon cable connector)  . Just try to knock with a screwdriver on the heatsink, or bend the board a little bit.

Regards,
Benjamin

Edit: O.Ops: Just saw that you destroyed the pcb in the next video ... so my post is obsolete

[bills]

Benjamin
Thanks for the tip I have one doing the same thing.
I opened it up and reseated all the t-con cables and it worked until I turned it off than same problem.
Now if i tap on the back it works until it cools off.
I will check and re flow that chip.
I  will report results.
This was a freebie that I use at my vacation home, may be a few weeks before I get back there.