Samsung PN43E440A2F – display turns off after several minutes

[diif]

Re: Samsung PN43E440A2F – display turns off after several minutes

Add some flux around the IC before applying heat to help with the reflowing.

[dick_barton]

Re: Samsung PN43E440A2F – display turns off after several minutes

Flux is really important so if you don't have any best to purchase some before trying. A good amount of flux helps the solder to reflow better under the BGA ic.

[heathloder]

Re: Samsung PN43E440A2F – display turns off after several minutes

Unfortunately, it looks like I was wrong. I tried re-flowing the BGA chip on the logic board after applying some flux, and now the display shows thin white vertical lines, evenly spaced about 1-inch apart all the way across the screen. The TV still shuts itself down after some random amount of time between 5 and 10 minutes if left to run.

I ordered a replacement logic board, since I probably irreversibly damaged this one, but now my attention is on finding the culprit that keeps causing the display to shut down.

I spent much of today re-examining all of the boards again, despite the possibility that the problem could still possibly lay with the logic board. I tried heating different components (lightly) with the heatgun while the TV was running to see if I could accelerate the shutdown, but the shutdowns seemed to happen with no correlation to my heat application.

Finally, I tried running the set with a fan over the X/Y-main and Y-Buffer area, and the set still shut down after about 10 minutes. I then tried pointing the fan over the SMPS/X-Buffer area, and now the set has been running for just over 45 minutes, displaying a Chromecast “screensaver”. This indicates to me that the shutdowns are definitely temperature related, and also definitely related to either the PSU or the X-Buffer board (due to where the air was being directed by my fan).

My thoughts are now back to the PSU. I took the X-Buffer board out earlier today and tested the transistors on the bottom of the board for continuity (in-circuit), and none of them showed any shorts, and the board looks fine otherwise, so I really think this has something to do with the power supply at this point.

If I don't get any suggestions, then I'll start by removing and checking the FETs that are attached to the heatsinks on the SMPS, but I'll be checking back here frequently to see if anybody can provide any advice on where to look.

Thanks again for all the help that's already been provided!

[dick_barton]

Re: Samsung PN43E440A2F – display turns off after several minutes

I would wait for the replacement logic board before looking any deeper into the fault and possibly creating another problem.

[heathloder]

Re: Samsung PN43E440A2F – display turns off after several minutes

So I got the new logic board in. Inserted it and now the vertical lines are gone, but the TV still behaves the same as with the old logic board (display shuts off automatically after anywhere between 5-25 minutes with the logic board LED going into a 5s ON/2s OFF flashing pattern).

In the time I was waiting for the new logic board, I spent a lot of time isolating the temperatures as best as possible on different boards. Regardless of which logic board I have installed, I can keep the TV running indefinitely (I've only been able to actually test for about 4 hours before trying other tests) by keeping a fan directed at the X/Y Main board. The SMPS board and X-buffer board don't seem to be adversely affected by temperature increase, and the Y-buffer board also appears insensitive to temperature.

I can't locate the exact problem area on the X/Y-main board with specificity, but it appears to be the transistors attached to the larger of the two heatsinks, ‘HS5000' (as outlined in the attached photo). Either that, or possibly a component on the underside of the board. I'm fairly positive it's not the transistors attached to the smaller heatsink, as that heatsink doesn't need to be cooled to keep the set running for hours, only the larger one (or at least that side of the board). I verified this by creating paper partitions to direct/prevent airflow to certain areas of the board, and then verifying the temperatures of the heatsinks by hand.

I found a replacement X/Y-main board replacement on Ebay, and Shopjimmy has a X/Y-main board repair kit (https://www.shopjimmy.com/samsung-bn...repair-kit.htm) for sale, but I'd like to at least try to repair the board (or at least fully diagnose the issue) before committing to buying a new one.

Is the best course of action at this point to try removing the components attached to that heatsink (HS5000) and testing them out of circuit? These components are labeled Q5000, D5001, and Q5001, from top to bottom.

[dick_barton]

Re: Samsung PN43E440A2F – display turns off after several minutes

I see that the two mosfets are driven by the 8 pin IC closeby. What's the part number given on it.

[heathloder]

Re: Samsung PN43E440A2F – display turns off after several minutes

The model was difficult to read off of the chip, but after fooling around a bit with a flashlight and magnifying glass, I was able to pull off the following info:

S4427
219P I<symbol>R
H8071

The datasheet for this IC can be found here: https://www.infineon.com/dgdl/Infine...5355d60b491822.

[dick_barton]

Re: Samsung PN43E440A2F – display turns off after several minutes

I wonder if it's this chip which drives those two Mosfets that may be running hot over time and not the Mosfets themselves? Just a thought.

[heathloder]

Re: Samsung PN43E440A2F – display turns off after several minutes

All thoughts are welcome! I appreciate any advice.

I will attempt to check this IC during my tests of the X/Y-main board. As much as I wanted to narrow down the issue, I'm considering just purchasing the repair kit from ShopJimmy, since it seems to come with three of those IC's (along with all the other transistors and diodes that likely cause issues).

I'm a little nervous that my tests at room temperature may not reveal the issue with the problematic component if it requires the higher temperature to actually cause the display to shut down. Any idea if I'll get accurate results if I test that IC in-circuit? I'm far more confident in my ability to remove and test the FETs/diodes than I am that tiny little IC...

[dick_barton]

Re: Samsung PN43E440A2F – display turns off after several minutes

Other than replacement I can't think of anything off the top of my head other than if you know the area it's in, then use a hairdrier to heat up the area of the circuit board it's under and shield the fets from heating up using a barrier ie something like a cardboard sheet.

The kit is probably the best idea at this time.

[heathloder]

Re: Samsung PN43E440A2F – display turns off after several minutes

I managed to find a good deal on the X/Y-main board on Ebay. Put the new board in, fired the set up, and it hasn't shut down in over 20 hours of use over 3 days. I'm a very happy guy right now.

FWIW, I pulled out the two IGBT's that I suspected were faulty (Q5000 and Q5001) from the defective X/Y-main, and they tested fine out of circuit (using a 12V power supply for supplying voltage to the gates), but I suspect that they wouldn't reveal their "imperfection" until their temperature was a bit higher, as in the case where the TV didn't shut down until the components reached a certain temperature.

Regardless, thanks for all the assistance!