Samsung LE40A676 takes several minutes to start

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

Thanks for your advices! I went for the easiest test first, which was just to heat up the main board a bit, using a hair dryer, and then try to start the TV.
That was a success!
After heating up the main board a bit, the TV started up immediately!
Does this brings us back to find the "bad C102" on the main board, or do we suspect something else?

[Davi.p]

Re: Samsung LE40A676 takes several minutes to start

Samsung A500 / A558 series is different from yours so you will not find same cap. Check the ripple on every el.cap. especially those with 3,3v or less on it.

[R_J]

Re: Samsung LE40A676 takes several minutes to start

Try isolating parts of the board with a piece of cardboard when you heat parts of the board.
This does not apply directly to your board, but C102 is a filter capacitor for a MP2363 step-down converter ic. It is possible that one of the caps on a similar ic is the problem.

[Davi.p]

Re: Samsung LE40A676 takes several minutes to start

With the luck he has of owning an oscilloscope the faster better way is to check ripple..

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

By heating the marked area I could make the TV start in a few seconds.
Now I can focus on finding the defective component.
Hope I'll be back soon!

[budm]

Re: Samsung LE40A676 takes several minutes to start

Since that area that you heat up has lytics cap (100uF 16VDC), you can try replacing that Cap (LOW ESR type).
Also, what is the designator and what is printed on that black rectangular component to the left of the IC1110?

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

The 100uF cap seems to be Ok but there is a MP2363DN (IC1110) that I've read from other threads that can be faulty...
At the moment everything points at IC1110. I took my Hot air soldering station and tried to focus the heat on IC1110 only, and when I did that, the TV started.
I can't say by 100% because some air may affec surounding components but there's a big chans that that's the component to replace!
Then I just have to find a place from where I can buy it...

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

My last test by heating with a soldering iron gave me the same result so now I'm as shure as you can get!
I found this one: https://www.digikey.com/en/products/...3DN-LF/5299123
But there's a "LF" at the end. Will this be Ok to use?

[Davi.p]

Re: Samsung LE40A676 takes several minutes to start

The 100uF cap seems to be Ok

Tested how? YOU MUST BE SURE..
Don't buy that chip, it is almost surely the cap, if you have one even higher capacity and voltage, solder it only for test on top of the old one and test the board. I'm wondering why you have the luck of having an o'scope and you don't use it , and i am 15 years repairing making money save without it.. last but not least.. caps improves with the heat, semicon the opposite..

[R_J]

Re: Samsung LE40A676 takes several minutes to start

If you don't have a 100µf to replace it, just parallel about a 10µf ~ 47µf across it to see if that helps.
I should add that this is just to test the operation, if this works, the 100µf would need to be replaced.

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

Thanks you for your commitment, and I'm sorry for not having mension it but I did try to solder a 33uF cap in parallell to the existing 100uF cap, but it was no difference. I've also measured the existing cap and it looks fine.
When I finally tested to heat the just IC1110 with my soldering iron, I'm quite convinced that this is the one!
I agree that it seems a bit strange, and I would not think that this was the the faulty component either, but at the moment, everything points at that direction.

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

And here's for you David.p, just to to satisfy your curiosity
The red line is the charging of Cap 1080 when powering on.

[Davi.p]

Re: Samsung LE40A676 takes several minutes to start

Try to substitute the cap, maybe it can go short and frees short on warming..
i can't see entire wave form..

[Chrille]

Re: Samsung LE40A676 takes several minutes to start

Hi,
I don't know what you mean with "entire wave form". That's the whole charging cycle. The start is when the TV is off and the end when it's powered on. Nothing more exciting happens later on. If the cap had been bad, I guess there would be a lot of ripple.

Anyway, now to the "solution".
I might be wrong here, but I'm quite convinced that the problem lies on IC1110.
Recently I "fixed" a defective graphic card just by heating it in the owen 15 min in 125 deg C.
I know, I didn't repair the card, but I made it work. Don't know for how long, but it's still working after a week. The two images shows before and after. This was NOT a fix for bad solderings and I'm not going to talk more about that here, but the temperature prove my words.
Since IC1110 is quite tricky to replace, and there's also a risk that I might damage the surounding components, I decided to try the same trick here.
The result was a success so far! I heated up IC1110 with my hot air soldering station (a lot more than before), and now is the TV working!
You might beleive that it's because someting else, and that's Ok. I won't argue about that since it works fine now.
The time will show how long it will work and if the problem comes back, I will take the risk to replace the IC.

But for now: The TV is working -> The problem is solved!
Thanks all for your commitment!

[Davi.p]

Re: Samsung LE40A676 takes several minutes to start

i did a mistake.