EEVblog #1154 - Surprising 4K Dumpster TV Fault

A surprising fault in the 4K LG Dumpster TV.
Using the block diagram and schematic to track down the likely culprit and reflowing the BGA's in an attempt to fix the fault.

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[rossmanngroup]

I'm going to send you some flux. You clearly do not have enough. :'(

[oriole]

Amateur mistake, but no worries, I've done it too. Never poke huge BGAs like that when heated. The pin pitch is very small, and you're almost guaranteed to form solder bridges. Watch out for the board warping temporarily from heat too. That in itself can cause solder bridges to form, or it can cause other BGA chips to lose connections. The board needs to be supported so that it remains flat when heated. Flux will NOT "undo" solder bridges. The surface tension will keep them together due to the small pitch. As long as you didn't short power to data, no damage should be done. This is generally unlikely anyways since power and data pins tend to be far apart for integrity purposes.

It will have to be reballed. It's not difficult to do, unless the ball pattern is something particularly weird. Since you've killed it already, just heat+lift the chip and take a look at the underside (you can take tweezers with L-shaped ends, bend the tips slightly so that they grab onto the chip's edges, and this way you can lift evenly/vertically). Make sure you do so with minimum "pulling", since otherwise you can rip out pads. Measure pin pitch (since that's difficult, you can just measure the distance between 10 balls and divide - less error that way), order a cheap stencil from eBay along with some solder balls, get some proper BGA flux (I use Kingbo RMA-218 which works very well and doesn't stink) and watch some tutorials. :) Do this not because you need to or because it's financially sensible, but just to have the experience so that future situations become simpler to deal with. How can you be the #1 electronics blogger without at least some successful experience reballing chips. Come on Dave! :) :)

[arthurvin]

Don't give up, try reballing yourself, audience wanna see continuation Dave.

[pirobotbeta]

When I worked at Nintendo at Kirkland, we had all the kit; Mantis microscopes, fancy Hakko soldering stations, air-pencils, vacuum rigs...you name it!
One bit of training they did was to allow folks to bring in dead consumer electronics with an eye at fixing them in the shop.
Get in a lot of practice working on other peoples mistakes!
A buddy brought in an LG TV, and over the course of 3 months every dang IC and transistor had been flowed off the PCB, cleaned, examined, put back on wrong, removed, broken, replaced, put back on right, you name it!
In the end it was a partly shorted by-pass capacitor...swollen electrolytic, nobody saw it!
Check yer basics first!

[mycosys]

IT'S THE DECODE ENGINE RAM!!! It HAS to be either that or the decode engine in the main chip itself - thats where the signal is being blocked. The signal is fed from there to the [B] Engine block which handles the OSD etc and clearly is working fine. The decode engine and the [B] Engine have separate DDR3 controllers, so the ram fault isnt affecting it. The display output looks like classic VRAM issues. A RAM fault is also vastly more likely than a processor fault

[draakevil]

I think the issue is quite obvious: You didn't use enough flux! Check out Louis Rossman to see what an adequate amount of flux is.

[JohnAudioTech]

Service flow chart: Abnormal display ----> place in dumpster.

[gamerpaddy]

phones without ir blaster work just fine.
get the IR code as a pcm wav / audio file, hook up a ir or even red led to the 3.5mm jack (if you got one lol) and play the file. i entered my lg tv service menu this way many times.

[__dm__]

for those who don't know, chris gammell is his co-host for The Amp Hour, a podcast about electronics

[MrAwyork]

COM port is for interfacing with an component controller. (Home automation type stuff.)

[Harindra]

Dave, would you like to go for another round, may be re-balling the chip. Don't give up

[peekpt]

It's the decoder RAM, because you have image movement, it's communicating but reading/writing wrong bits. But I think you toasted it, these operations must be temperature controlled

[aurthorthing]

I don't see ads because ad blockers.

[DedmenMiller]

Well reflowing that chip, changed the output... So either you fixed something partly, or you just broke it completely and the error was actually before that chip, and because you broke it you didn't even get far enough to encounter the original problem.

[bryandepaepe]

Some initial tests for BGA would be applying pressure with your finger while TV is on and looking for any change in picture, cooling and or heating chip when TV is on looking for a change in picture. When attempting reflow look at near by soldered components for any solder melt which would indicate that the BGA is also melted instead of touching chip for movement.

[cavemanization]

Good to see Dave come a gutser every now and then. Makes me feel a little bit better.

[gavincurtis]

Reball it! You can listen to Tom Petty's "Re-balling" to pass the time while doing it.

[BenHeckHacks]

I'll cast another vote for a Dave Jones Loius Rossman shared universe! But yeah shipping between these countries is either super slow or super expensive.

[idlegandalf]

I think you meant the video decoder. The encoder would be for recording stuff, decoding is what was to be done to view video encoded in codec x.

[ReNeyer]

Let me shed some light as to why the RS232 Codes are listed in the consumer manual. This is a former top of the line, home cinema TV. Most professional and home made installs for home cinemas work with universal remotes who send RS 232 codes via wire to devices such as the amplifier, tv, screen and sometimes even curtains and such. Hence these are included because the consumer really does need them. I worked in a small scale cinema (1 screen) for about 5 years and we used this system.