Baking HDMI board to repair TV

[---k---]

I have a less than 2 year old LG 4K tv that has decided to stop accepting HDMI input. I get no signal error. The internal Netflix etc. works fine. Searching the net I found a site that claims if you remove the HDMI board and bake it at 385* for 10 minutes it will fix the bad solder joints and good to go. http://zedic.com/lg-42dl550-fix-repair/

Does this make any sense or sound reasonable? I can sort of see how it'd work.
I'm told a repair shop is $100 to look at and final repair likely 400 for a new board. It was a $900 tv when I got it. I'm thinking $400 is too much for this set. So trying the baking is intriguing. But since Netflix and Amazon work for now I'd hate to do something that'd kill it completely.

Thoughts? Is this a hoax like drilling a hole in you're iPhone or legit option.

[Kevin P]

If it's a solder joint causing the problem, it just may work. They assemble the boards in the factory by running them through a soldering oven so it's similar conditions baking it in your own. You just have to make sure it's completely cooled down before reinstalling it of course, and make sure to remove any plastic pieces that may melt at such temperatures.

Reading the article, they mention tin/lead solder. Nowadays most electronics uses lead-free solder, which requires a higher temperature to melt and reflow (it's this lead free solder that leads to many failures due to failing solder joints). You might try 400F instead of 385.

I own a hot air soldering station so I can fix issues like this more precisely, at least if I know which joint is bad, I can direct hot air into just that spot on the board.

[Alaric]

It works-sometimes-sort of. I've done it with the PCB from a flash drive and some computer graphics cards. The PCB is quickly placed on a piece of aluminum foil on the oven rack after pre heating and the oven door closed. Watching through the door window, with the light on, watch for the solder to turn shiny. It isn't a slow process, it all turns bright at the same time. As soon as you see that you must open the oven and remove the PCB immediately. The "oven trick" may work on some components. This is definitely a try at your own risk deal. It frequently doesn't last long. Here's some fixes and fails, along with how they did it. http://www.overclockers.com/forums/s...ght=oven+trick

Your TV has a warranty period shorter than two years?

[---k---]

Thanks guys. Still seeing if I can get lg to repair it. Also trying to find a better deal on the part. Problem is I have no way to know it is the board for sure until I buy a new one.
Yeah. 1 year warranty is what the website says.

[Alaric]

It's definitely more of a last resort than a go-to procedure. I've had varying levels of success and failure with it over the years. If you end up trying it, use caution. Those metal bodied capacitors take a few minutes to cool down. When/if they fail they can shoot a nice little jet of flame out one end, with a nice little "pop" sound. There is also the risk/certainty of damaging the thermal pads under the heatsinks. The picture in the article in your link shows a sticker on the upper right corner, with a barcode. Google the model and serial numbers, along with the numbers printed on the back of the PCB. You may get lucky and find a cheap source for a replacement part. Or maybe find what other model TVs that board is used in and find one with a broken screen on Craigslist cheap.

[xandresen]

I second Alaric's last post: "last resort".
We are hoping a bad solder joint is the problem, that remelting the solder will fix this (not necessarily so), and not create additional bad solder joints. If the bottom side of the PCB also has surface mount parts, I don't know quite what happens. Be sure they won't get get pushed out of position by the pressure of the oven rack while the solder is molten.

I suggest setting the oven at 450F as the melting point of many lead free solders is about 400. The old lead-based solders melted at lower temps.

400F will destroy electronic parts if their insides are allowed to heat up to it. We have a little time as the PCB heats up a bit sooner. That's where his phrase "remove the PCB immediately" comes from.

So better to have the oven a little too hot than too cold (where the solder doesn't melt and you cook things to death as you wait). I would also suggest not letting the oven heating element come on while the PCB is in there.

Not sure I would try this unless no other alternative but good luck if you do.

[Steve Manning]

Hey Ryan, a trick I've used in the past hunting for bad solder joints ...... if it can be done, power the TV up with the board exposed. With a Non-Conductive item (wooden craft sticks work great) go from joint to joint and gently push down on the connection. If you can get things make contact and start working, power down and just hit the joint with a soldering iron and re-flow the solder. That way you don't need to stick your board in the oven creating all kinds of additional problems.

[---k---]

Thanks again everyone for the tips.

I got a work trip coming up this week. Once I get back, I'm going to have to unmount it and take it apart and see what can be seen. I'll google the part and see if I can order it. But, if I'm ordering the part, I might as well try the oven and destroy the old one first. My biggest concern is that the oven may short something that once I plug the board back in that it damages another part of the tv.

LG has a repair shop listed on their website not far from me. I could probably get the part from them. I've called them and left a message, but they haven't called back.

[BobEllis]

You may have already tried this, but my old JVC has an interlock on the HDMI boards - it shuts off the HDMI inputs if light gets to them (like you're tampering and trying to get video or sound out) they turned off. A pain, because if light came in the "right" way and it was near a window no more HDMI. Some reported random turning off. At any rate there was a reset procedure that could turn them back on. Perhaps your LG has something similar.

[Kevin D]

Pull the back off the TV, get the board model and buy another.

ShopJimmy, tri-state module, and several eBay sellers other returns. If it doesn't fix it, return it. If it fixes it, bake the other one and see. If it works too, you have a spare.

I fixed a Dell motherboard with the oven trick. Lasted about three months, did it again just to easily copy everything over.

Kevin D.

[fbov]

If you do try the oven method... include flux.

There were lots of issues with Onkyo HDMI PWBs. Every reflow procedure included copious flux.

I like the "press on connections" approach, but not for the faint of heart. There are really dangerous voltages back there.

Have fun,
Frank

[---k---]

Ugh. Yes. I'm a victim of the onkyo HDMI problem too. I returned mine twice already like three or four years ago and got free including shipping repairs. But last year before I move it seemed like I was starting to get intermittent bouncing again. I need to get it out and test it and get it repaired. But it was so intermittent I thought I was just crazy. I'm so far from having the basement room ready to hook everything up. Im hoping to be in a place that when I do hook it back up I'll be able to justify a new fancy receiver.

[fbov]

Ugh. Yes. I'm... hoping to be in a place... to justify a new fancy receiver.

+1

Atmos is one justification. In my case, I need a 12v trigger signal to use the XPA5 under the kitchen table. Who includes a full set of pre-outs, and no way to turn on the amp they lead to? The Zone-2 work-around doesn't appeal (Onkyo 707 Zone 2 has a 12v trigger output...).

Then again, neither does the conversation explaining why I need to spend another $1K in order to use what I bought with the first $1K.

HAve fun,
Frank, who only needed it fixed once.

[5th element]

Including flux would be a great idea but would be rather difficult in the more modern LGA/BGA packages. Still, baking is a worthwhile approach, but only as a last resort.

Lead free solder is a lot harder to bake than a nice eutectic lead/tin mix. We're talking 180 degrees Celsius vs 260. Not to mention the fragility of lead free solder itself. The military and aero-space industries still use lead solder for its significantly improved reliability vs that of the newer lead free stuff. Makes you thankful that they do when you consider the rather alarming failure rate of some consumer products based around the lead free process.

Instead of oven baking you could always use a hot air gun, like the kind you use for paint stripping. I use one of these for gross desoldering of SMT boards and quick reworks. If the chips used have external legs then apply flux liberally and heat the board with whatever method you prefer. Plastics parts are designed to survive reflow but they do still soften so you'll have to be careful.

[---k---]

Minor update. Pulled the back off of the tv today. I didn't see any loose connections or flame marks. So I Got the part number and google found one in stock at tvpartstogo.com for $85. The sites Kevin mentioned above were out of stock.

Way cheaper than I expected. Part on order. Should be very easy to swap out. It is used but crossing fingers.

Part looks the same as their photo, except mine has what looks like a ceramic cap over a few of the chips. Thiers doesn't. This is there photo. https://cdn.shopify.com/s/files/1/11...g?v=1471835494

It's not the black heat sink. It is a big white cap that has the feel of a sand cast resistor sitting on top of the chip with XD on it plus a few adjacent. I'm guessing this is something to protect the chip from tapering and copy protection. But that's really a wild guess.