Samsung UN55ES550F Tcon Fuses

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

CO43 Bingo budm.


With CO43 removed, every point previously at 0.7 Ohm and days earlier a wee bit more.... are now at 2.76 kOhms relative to chassis ground point.


The other sides of the caps and resistors we talked about are all still at 0.1 Ohm or maybe lower.

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I'm not really sure what it means, but it looks like we used an ohmmeter to find a badcap ?

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I'm sure there must be vendors docs on devices and components, how do I learn to identify these unmarked bits.

From probing around, I think R J is spot on with the missing resistor, it's probably going to be close to 1 Ohm.

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In this particular removal I switched nozzles, as I'm trying to get the feel for the rework unit. I was planning on pulling the adjacent cap, I thought it's solder shined, and my tweezie, hit CO43, so I cleared it first.


So while the first attempt has changed things, and the other pieces are still there... I blinked.

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Let me know what's happening and what's next?

[budm]

Re: Samsung UN55ES550F Tcon Fuses

Are you sure the C043 is shorted?
"Per your report: CO43 6.3 kOhm.
Can I see closed up pictures so i can see how that shorted cap is connected?
I use Ohm mode, usually 200 Ohms scale to look for low resistance on the suspect bad parts.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Sorry. There is an error in Post 21

It was/is CO46.


I was heating CO45/46 and I moved and then removed CO46.


Now all the larger tan caps and all the previous points tested on that line are now at 2.76 kOhm.


I just tried the resistance across the removed tan cap and after it raises through a transient, it then steady's down to 0.5 Ohm.

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Yes on the pix, my best bet is with natural light; so it'll be several hours.

[budm]

Re: Samsung UN55ES550F Tcon Fuses

CO46 is connected in parallel with C045.
Since the shorts circuit is now gone, the T-CON should now work without that C046 for now so you can do quick test and see if you will get the pictures on the screen now.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Great. I'll need to chase down a wee resistor to finish the rest of the reconnect on this board.

That's my RD03 issue.

In passing, is something like Artic Silver or an Antec paste suitable for reinstalling, well actually installing, the bigger proc's heatsink on the Tcon?

This heatsink was never in contact with the processor. The adhesive in the sink has only a teenie spot were there was less than casual contact.


It's just a bad match between the standoffs and the pushpins.

(Pix will follow.)

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

I'm adding the better resolution Tcon photo to complete the record.

It also shows the CO46 removed and the processor w/o heatsink.

Those little spots are the only bit of heatsink adhesive from where the minor contact occurred.

From the side elevation you could clearly see a half mm air gap between the plate and the processor.

Essentially, it was a thermal umbrella, with a bit of sympathetic convection of the air gap.

The underside of the sink shows the goo in near pristine condition.

Lovely.

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Is it a good way to ID the bad cap, by removing a believed-to-be-good sister, and have that measured at the parts house?

[budm]

Re: Samsung UN55ES550F Tcon Fuses

https://www.badcaps.net/forum/attach...6&d=1569126456
I cannot find RD03 in that picture.

[petehall347]

Re: Samsung UN55ES550F Tcon Fuses

https://www.badcaps.net/forum/attach...6&d=1569126456
I cannot find RD03 in that picture.

far right edge near centre .

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

I'm going to try to get some resistors and replacement cap today.

I looked at other small small resistors in the immediate area to RD03:

I used three meters, and they all reported that the resistance was just about what they each would read if I held both probe tips together. About 0.2 ohm or 0.1 ohm going to zero if I held it.

The resistor over at RD121 is showing 100 Ohms consistently.

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I didn't look closely at the trace but that pair of itty bitty ones RD106/108 I can not get the meter to move. I know it's tight in there, but they show as open ?

Anyway, I'll grab what I can. My choices tend to get decided for me with inventory.

(Guidance on best practice is welcome.)

[budm]

Re: Samsung UN55ES550F Tcon Fuses

I would expect that RD03 will be really LOW Ohms (<10 Ohms), if you look at the application circuit, it does not have any resistor on pin 19 to the output of the Boost converter.
What is the resistance RD10?

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

I omitted the label, sorry.

RD10 and also RD25 (this side of DD1) are both reading about the same as each meter's short output : 0.2 or 0.1 ohm.

With either style meter, ranging or 200 ohm.

Quickly after probe contact they are about an ohm, then steady drop if I stay pressed.

[budm]

Re: Samsung UN55ES550F Tcon Fuses

At this point I do not know why they put that <1 Ohm resistor in place, may be they try are trying to use as Fusible resistor. For testing purpose you can bypass it for now.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

budm,

I did make it to the parts supply. I came to that conclusion after visiting with a fellow there.

While they didn't have smd's that size, there were conventional resistors at 0 or .11 or 1 ohm.

His comment was, something about treating it like a fuse.

Now, if that is probable, and they had a reason for placement, do I need to look harder at the readings I have at RD106 and RD108 ?

They sure seem to be open to me. I can't get a reading on any of the three meters.

At some point, if all goes well, I'll order some smd resistors. Any of those three are probably fine. I think I'll get the .11.
_____

Also, I did remove the sister cap CO45 and took that along.

It's reliably reading 46 picofarad, and 47 is popular, so I grabbed 47 picofarad, 50 volt, same physical size as the existing.

I realize there are other parameters, but I don't have them anyway, so I have these to install at CO46.

I'll get the board back in the set in some fashion in the morning, and continue the tests.

[budm]

Re: Samsung UN55ES550F Tcon Fuses

I think at this point the cause of blown fuse is due to shorted C46. As far as RD03 resistor is concerned, you can use any low Ohms resistor, I.E. 0.47, 1.2 Ohms 1/4 through hole resistor for testing to see if you will get the AVDD Voltage back or not.
You did not find any other shorted caps, correct?
Failure mode of those MLCC is shorted circuit or low resistance, you have handle them carefully since you can crack them easily if you do not handle them properly, always check the resistance after replacing them to make sure you do damage it.
BTW, are you sure the caps only show 47pf? That seems very very low, I expect it to be at least 0.1uF 35V minimum.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Rodger that.
I was on a manufacturer's site trying to understand sizing and I saw all the installation and handling recommends... including no metal tweezers.


Then when I removed the mlcc it stuck to my tweezers like that resistor did.

Anyway, I have a better strategy going forward. And a half dozen 47 picofarad JIC.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Boys... and ladies, I believe we are fixed.


Or at least the big pieces. I have no input signal, or specific remote, and I don't have a support frame, so I just slide a few inches off the edge to peak, but the snow looks damn good..


(Yeah checking a Kuro that way is tricky. It's all black.)

So, what I did.

I replaced the shorted CO46 with the one that seemed right or close from the parts house.

I replaced CO45 to it's original pre-test pads.

I fashioned a divining rod / heart shape legged replacement 1 ohm resistor with the legs being the maybe thirty thousands of an inch apart and then the tiny ends pointing in opposite directions while parallel to the board.

Then I cleaned all the flux off all my tweaked areas with alcohol, and that seems to have done what I hoped.

I then tested all our now favorite points:

1 ohm is now in the trace to pin 19. There is no short at the adapted resistor.

Both CO45 and CO46 are contacting and showing the same 2.7_ kOhm resistance.


And finally with the flux shield removed, both RD106/108 are now showing just over an Ohm.

So, when plugged in, it went through a start dance. Since I never saw one of these start, I'm not sure if it's all according to hoyle, but with it ending at snow, I'm guessing it defaulted to antenna.

I've got plenty of Samsung Plasma Remotes, so after I get the bezel/back all snugged up, we'll go vertical and have a look.

R J, budm, budwich, neilc6 and everyone playing along at home, thank you for your time and help, it is very much appreciated.


PS: For now, and looking at the resistance at RD106 does it seem like a 1 Ohm is the correct smd to order in, or are all of them, down to zero, pretty much a pick 'em, as we've been saying?

[budm]

Re: Samsung UN55ES550F Tcon Fuses

I would put the RD106/108 back in place. Were they damaged?

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Oh well.

The panel has some 'clouding' in both lower quadrants. it's pretty irregular shapes, but you can see the pixel intensity differences, so that's that.

This image quality thing is consistent on all the screen real estate.

There is a bunch of information missing. That's as bright as it gets. And looks better in the photo.

Everything is seems posterized, and looks like whole areas of the color gamut are just gone or real weak.

I'm just begging the question for info purposes, what in the set has control over this, if the input signal itself is fine. (The snow did look good too, if a bit magenta.)

Anyway, have a good weekend.


budm, just saw this. I left the RD106/108 alone, they tested at 1 Ohm apiece after I got all the flux away. I'm not sure the flux was it, just that's when I got good readings.

My point was simply do they being 1 Ohm make sense that RD03 is suppose to be 1 Ohm. (I see I didn't label that in the post above, RD03 is where I made the heart shaped fixit through hole resistor, sorry.

[budm]

Re: Samsung UN55ES550F Tcon Fuses

That is GAMMA issue.

[Renovator]

Re: Samsung UN55ES550F Tcon Fuses

Thanx.

I'm on it.