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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

03-04-2019, 10:53 AM
Re: lg 60ld550

I watched that video and I read, and read, and read, and I watched some more videos. A lot more. I now know more about BGA chips and BGA "Flip Chips" than I ever thought I would - or would want to.

While I doubt that these chips were initially designed as "planned obsolescence" for the components that they are used in, they have certainly become that. This design, combined with lead free solder, really has no alternative but to fail. Just poor design all the way around. Just terrible. Cheap and fast to manufacture...

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Last edited by BCM_OC; 03-04-2019, 11:56 AM.
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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-27-2019, 02:44 PM
Re: lg 60ld550

Well, I would be very interested in seeing that. Let me know if you find it.

Planning to do this re-flow experiment this Saturday. Hoping that the flux doesn't cause the existing solder to flow or "pool" to one area under the chip, but I guess if that were the case then it would occur during manufacture and re-balling type repairs. I can't really see why it wouldn't work with some flux added in for good flow and wetting. A hot air station is how they heat up the chip for re-balling anyway, so this is essentially the same thing....

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-27-2019, 11:50 AM
Re: lg 60ld550

Failure how? What happened?

Here's what I'm (now) thinking - Tape the components on the underside of the board (under the BGA chip) with polyimide tape. Support the board under the area to be re-flowed with a polyurethane foam block, and place an aluminum foil "heat shield" in between the foam block and the taped underside of the board. This way, even (and isolated) pressure will be maintained on the underside of the board in the area that is to be heated - in order to keep the components on the underside from dislocating as...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-27-2019, 10:32 AM
Re: lg 60ld550

I agree with you. Honestly, I'm very surprised that if the solder is hot enough to "reflow" anything, that components don't fall off the back side of the board during this whole board "baking" process. I understand that there is some surface tension at play, but that's not holding anything more than SMD's. Given that, (like you) I'm of the mindset that local heating is actually "healthier" for the board than having the entire board get baked - despite the "shock" from temperature differential as some claim. Maybe...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-27-2019, 07:28 AM
Re: lg 60ld550

Well, I ended up taking your advice, and [B]it worked!![/B] When it came on I was like, "Son of a ..." Then I was like

Last night I ended up going over the power supply schematics, board traces, and my earlier test results. I realized that the mosfet on the power supply board that I thought was "shorted", would actually require removal for proper testing, and that it might be OK after all.

So, this morning I decided to give your idea a try. I kind of figured that I really didn't have all that...

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Last edited by BCM_OC; 02-27-2019, 08:03 AM.
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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 04:49 PM
Re: lg 60ld550

I was really hoping to avoid that "repair" if possible. Need to see what I have here, though. At this point I'm not sure what's good and what isn't....

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 04:47 PM
Re: lg 60ld550

Yes.

Something funky is going on with that power supply though. I got a little tingle when I brushed up against one of the heat sinks. Stuck a meter on them and one is over 60 volts and the other is around 32 volts. (see pics) One of the outside legs on one of the mosfets is shorted to ground. Time to freshen it up I guess.

Somebody must make component kits for these, right? Any suggestions?...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 01:11 PM
Re: lg 60ld550

Here is a pic I found on Ebay of the same board. It is in the listing for a board repair service, and if you look closely at that IC (top, just left of center) you can see that it [B]does not[/B] have any solder bridge between the terminals.

It's here; [url]https://www.ebay.com/itm/Mail-in-Repair-Service-For-LG-60LD550-Main-Board-1-YEAR-WARRANTY/232391789934?hash=item361ba14d6e:g:QZIAAOSw~XpZVY-p:rk:26:pf:0[/url]Re: lg 60ld550

Here is a pic I found on Ebay of the same board. It is in the listing for a...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 01:05 PM
Re: lg 60ld550

I did. I just may not have explained it well enough.

Here is that 4th picture of the power supply connector again. If you look at at the three [B]12V[/B] terminals on the right side, I have 12v (11.7) there. However, on the opposing terminals on the left side of that connector I [U]do not[/U] have any voltage.Re: lg 60ld550

I did. I just may not have explained it well enough.

Here is that 4th picture of the power supply connector again. If you look at at the three [B]12V[/B] terminals on...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 12:40 PM
Re: lg 60ld550

Well that's on pin 18 (INV-ON) on [B][I]one[/I][/B] side of the connector.

What I [B]don't[/B] seem to have is 12v on 17, 19, and 21, which would correspond to "INV-ON" (17), "A-DIM" (19), and "P-DIM #1" (21)

I don't know which side on the mainboard connector is input and which side is output.Re: lg 60ld550

Well that's on pin 18 (INV-ON) on [B][I]one[/I][/B] side of the connector.

What I [B]don't[/B] seem to have is 12v on 17, 19, and 21, which would correspond...

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Last edited by BCM_OC; 02-26-2019, 12:42 PM.
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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 12:31 PM
Re: lg 60ld550

Good catch. After posting the pics and schematics earlier, I just kept looking at the board and the schematic. I ended up taking that solder bridge off - as it didn't seem necessary for legs 1 and 2 (already going to ground) and leg 3 is connected to a 3.5v trace with a 47.5 k resistor.

My thought was that maybe it was a repaired board and that was done in error and it was maybe pulling down the 3.5 v trace. Either way, it made no difference to the current issues. Hopefully it (IC) didn't get damaged if it was incorrect before. Wish...

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 12:16 PM
Re: lg 60ld550

Thank you.

When I test as you asked, I get a little over 4 volts on that terminal (18) on power up, but then it drops off rapidly to just over zero.

Here's a schematic for the power supply and the P8000 connector on the main board, and pictures of each. The harness connects these two connectors pin to pin....

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BCM_OC replied to lg 60ld550

in Troubleshooting TVs and Video Sources

02-26-2019, 07:27 AM
Re: lg 60ld550

Long time listener, first time caller.

Was going to start a new thread, (and will if that's what the Mod's want me to do) but I seem to be having the same problem with the same LG model 60LD550 TV, so I thought this might be the best place for it. Hopefully you guys can help me out.

So, here's the story - This TV went out on the previous owner, and they attempted their own repairs before finally giving up. Previous owner stated that they replaced the main board, but that didn't fix it. I first thought that this meant...

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