Y sus test - ebr31650403

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Hi, I have just took delivery of this board and I think it is faulty, can someone just confirm please, it is the Ysus with that stupid IC under the heatsink

I am getting continuity between the +5v to gnd on the chip under the large heatsink and the track on the 18v line looks a bit battered.

[tom66]

Re: Y sus test - ebr31650403

Yeah, that's bad -- it's probably a failed refurb, another example of a dud, untested board from eBay or other sites. Ugh.

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Re: Y sus test - ebr31650403

Yeah, that's bad -- it's probably a failed refurb, another example of a dud, untested board from eBay or other sites. Ugh.

Grrr yep £76 and 1 week later to take delivery of a crock of crap, but then again tom it is my on fault for trying to be clever.

The board that had blown on me was "board b" (pictured) (3 fets had blown) and I know "board A" will fit and work, exactly the same connections across the board.

Tom could I ask if the 3 fets on board b had blown does it normally take more out or do you think changing the 3 fets would get the original board working again

Cheers

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Re: Y sus test - ebr31650403

Attachments...sorry forgot to add the pictures

[tom66]

Re: Y sus test - ebr31650403

The boards are completely different, the control board WILL NOT (should not????) work with a different board due to differing sus/ER waveforms. Discrete board firmware different to IPM board firmware.

Bad FET usually kills gate driver and other associated components.

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Re: Y sus test - ebr31650403

Oh, see I told you it was me trying to be clever, I always thought that when the same connections labelled exactly the same would work, but then thats probably me thinking ahead of myself as I have bodged incorrect PSU's to work in LCD's with no problems

And to top it off I have just found the correct y sus for £28

[tom66]

Re: Y sus test - ebr31650403

Send the old one back, it's bad, buy the new one, sorted?
Power supplies are pretty universal if you can make them fit, most other boards aren't.

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Re: Y sus test - ebr31650403

Bad FET usually kills gate driver and other associated components.

Hi Tom, could you go a little further into this please.

I have found that out of the 4 fets only 2 of them have blown, and at £4.00 each I think it might be worth a punt, I would replace all 4 to play safe, thats if you could give us a couple of pointers what to check and that they aint blown

I have pictured and circled the two fets that had blown

The fet part numbers are RJH 3047 (Silicon N Channel IGBT High speed power switching)

The TV in question is an LG50lc55 and the ysus Pn = ebr39522801

Thanks for any help

[tom66]

Re: Y sus test - ebr31650403

You really need a scope to test it properly.
You should test the 14 pin chip near those IGBTs for shorts to ground (use screw mount etc.)

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Re: Y sus test - ebr31650403

Cheers Tom

The chip on the right is fine, no shorts only pin 7, which is the gnd pin

The chip to the left (IRS21064S) is showing continuity through pins 5 and 6
Pin 5 is vss and pin 6 is com, looking closely at the board it looks like their is a track between them too

Just looked at the Datasheet for the ic again and vss is "logic ground" so I am guessing this ic is ok too

If these two ic's are not showing S/C's would you take the risk of popping 4 new fets in

[tom66]

Re: Y sus test - ebr31650403

They look good... Also check continuity between: HO and Vs, Vb and Vs, Lo and COM. All should be open. If so, you should only need to replace the FETs.

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Re: Y sus test - ebr31650403

Also check continuity between: HO and Vs, Vb and Vs, Lo and COM.

All open :o)

Thank you I will report back to let you know if the tv works upon replacing the 4 fets

[tom66]

Re: Y sus test - ebr31650403

Just noticed Q2/Q3 etc near the 14 pin chips. Do you see any shorts on those either?

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Re: Y sus test - ebr31650403

Just noticed Q2/Q3 etc near the 14 pin chips. Do you see any shorts on those either?

No they are both fine

[tom66]

Re: Y sus test - ebr31650403

And the other two? Just to be sure.

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Re: Y sus test - ebr31650403

Cheers Tom

I am getting s/c to gnd on the pins highlighted on the pic mate

[tom66]

Re: Y sus test - ebr31650403

That's fine, those pins are connected internally for the package type SOT89 (which those are.)

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Re: Y sus test - ebr31650403

That's fine, those pins are connected internally for the package type SOT89 (which those are.)

Thats a shame I was looking to rape the faulty £76 board I was sold of parts before I sent it back ;o)

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Re: Y sus test - ebr31650403

Hi, Well the fets arrived fitted them and TV powered up, no problems, the problem lies in the picture, sorry I didnt get a picture to show you but I will explain as best I can, the horizontal lines are no particular size or uniformed in anyway, 1 line is white about 4inches wide 2 inch black band 3inch white band 2inch black band and at the bottom of the picture a purple speckled haze with a grey looking background, after a couple of minutes being on the tv started shutting down again and rebooting

Can I just add that the TV has been sat in a cold damp garage for 9mths and just took every ounce of our lovely winter.

When the tv started shutting down I thought the fets had blown again but no the board is still fine

Any ideas, is this a buffer fault or the worse case scenario the screen itself

[tom66]

Re: Y sus test - ebr31650403

LEFT to RIGHT lines
or TOP to BOTTOM?

LEFT to RIGHT: Reseat the panel connectors on the Y-buffers, common problem especially with 1080p screens.

TOP to BOTTOM:
More than approximately 2 inches: Reseat panel connectors.
Less than approximately 2 inches: Unrepairable fault due to panel driver failure.

All panel connectors only to be reseated with power OFF.