Hyundai LCD with bad caps - how bad can it be?

[jazen]

Hello, this is my first post in the forum and wow, what a great resource! A few months ago, my friend found a Hyundai LCD that his office chucked into the garbage and gave it to me. Not knowing what the problem was, but always wanting another LCD, I decided to open it up and have a look. The most obvious issue is the power supply board. It shows 2 bulging Samxon 470uF 25v capacitors in a cluster of 5.

Since it doesn't power on at all, I'm wondering if that's the extent of the damage or if there's more. And how can I go about testing the capacitors and any other possible components?




And there's some minor burning on the other side of the board where these 2 chips are (upper portion of last picture)

[Player2]

Re: Hyundai LCD with bad caps - how bad can it be?

Definitely start by replacing all of those caps on the power board. I wouldn't worry about testing them, there aren't that many that the cost is going to be prohibitive. I just did a Gateway last week with a similar board that had those same Samxon 470's. Two were visibly vented. I went ahead and popped off all of the caps- two more that looked ok from the top had blown the rubber bung out the bottom. After recapping it worked like a champ.

[berniedd]

Re: Hyundai LCD with bad caps - how bad can it be?

What series are these failed Samxons?

[Toasty]

Re: Hyundai LCD with bad caps - how bad can it be?

Replace ALL the caps on that board, as stated by Player2. I see 9 so far in your picture. Include any others.

The "burnt" area on top is heat from the transformers. Around the chips below, it appears to be leftover flux from factory soldering. Not to worry. Resolder all the pins on the 2 transformers, as this is a common area of failure from "cold" solder joints.

Toast

[jazen]

Re: Hyundai LCD with bad caps - how bad can it be?

What series are these failed Samxons?

The only numbers I see that aren't temperature or ratings are C8 and U3A and KM(M).

The burn areas coincide with the 2 chips (which turns out to be MOSFETs) in the second photo.


I guess I'll submit a cap request on the site.

[Toasty]

Re: Hyundai LCD with bad caps - how bad can it be?

SamXon KM series datasheet:

The MOSFET's get hot during operation and the bad caps don't help the situation. What you're seeing is discoloration from the heat.

4502C Datasheet:

I don't see the 470uF @ 25v caps on the site charts. Ask and see. You may need to order from Digikey or Mouser.

If there is a height restriction, you'll need to bear that in mind when choosing replacements. Those 470uF KM's list as being 10x12.5mm. If you can go to 16mm tall with no problems, then Panasonic FC's (and others) should fill the bill nicely.

Check the fuse also. Since you said there is no power, that and other components may have failed due to the caps. The inverter may also have a micro-fuse on it, so a top-down shot of the whole board will help.

Make a list of the quantity and values of all the caps along with their dimensions in millimeters. Post back.


Good Hunting!
Toast

[PCBONEZ]

Re: Hyundai LCD with bad caps - how bad can it be?

KM = Series
http://www.manyue.com/upload/product...prodPDF_31.pdf
They aren't even Low ESR caps - but should be...

(M) = uF Tolerance = +/- 20%.
Most electrolytics are +/- 20%.

[Wizard]

Re: Hyundai LCD with bad caps - how bad can it be?

Shouldn't blame the Samxon, especially when makers chose to use not low-ESR capacitors. This is what you will get this problems like this. Ditto to electronic suppliers like globalsemi does. All general caps not low ESR, means more call backs to our repairs.

I even had to resorted to ordering capacitors outside of global's from other reseller.

Cheers, Wizard

[jazen]

Re: Hyundai LCD with bad caps - how bad can it be?

Sorry for not replying sooner, I was out of town for the last couple of days and just got back tonight. Here's a photo of the top of the board. I don't see any visible fuses on it though, however, there is a warning about a fuse printed on the board.



I'm not sure if size is a concern, seeing as the fuses aren't even the tallest components on the board, I think I'll have some room to play with.

[jazen]

Re: Hyundai LCD with bad caps - how bad can it be?

(Tried to add this but ran out of time)

And the capacitors are as follows:

5x 470uF 25v (black) 13x10.2 mm
1x 470uF 25v (green) 13x10.2 mm
1x 470uF 10v (black) 12x8.2 mm
1x 47uF 50v (black) 11x6.5 mm
1x 1uF 50v (purple) 10x5.3 mm
1x 68uF 400v (black) 30x16.1 mm

I also tested the fuse (F101) next to the power cable plug on the left. It seems to test out fine with no resistance.

[Wizard]

Re: Hyundai LCD with bad caps - how bad can it be?

Take a good picture on other side of circuit board. There should be a fuse or two somewhere.

Cheers, Wizard

[jazen]

Re: Hyundai LCD with bad caps - how bad can it be?

Wizard,

Here's the back side of the board.



I think the only fuse is the one on the top side, I had to research it last night to find out the black cylinder between the power plug and the "CAUTION!" label was indeed the fuse. Other than that, there's no other fuses.

[seanc]

Re: Hyundai LCD with bad caps - how bad can it be?

I'm pretty sure the fuse is F101, on the top of the board.

I repaired an AMW monitor's bad capacitor, with a general purpose Jamicon the other week just to see if it works - it does. Before, it didn't turn on at all.