Blown IC

Stu jaxon

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Apr 1, 2021, 2:04:27 PM4/1/21

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Hi Group, need help identifying a blown IC. it's on Vizio e550-b2, power supply board # DPS-167DP ,.. Board locator # ic901, it has 7 pins, and the top is blown away.??

Adrian Caspersz

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Apr 1, 2021, 2:33:50 PM4/1/21

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On 01/04/2021 19:04, Stu jaxon wrote:
> Hi Group, need help identifying a blown IC. it's on Vizio e550-b2, power supply board # DPS-167DP ,.. Board locator # ic901, it has 7 pins, and the top is blown away.??
>

You missed an 'I'

Googling is remarkably effective with the right input.

e550I-b2 ic901

e.g.

https://www.badcaps.net/forum/showthread.php?t=79046

https://www.badcaps.net/forum/showthread.php?t=70423

Apparently a LD7913JGM6, a PWM controller?

--
Adrian C

Stu jaxon

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Apr 6, 2021, 8:35:31 AM4/6/21

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I have a .068 ohm resistor reading 0.00.. acting like a short, it is a low ohm resistor, is it supposed to read???

Stu jaxon

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Apr 6, 2021, 8:37:54 AM4/6/21

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board part # R804A...

Message has been deleted

ohg...@gmail.com

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Apr 6, 2021, 11:26:35 AM4/6/21

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On Tuesday, April 6, 2021 at 8:35:31 AM UTC-4, Stu jaxon wrote:

Did you zero the meter? Sometimes a low value resistor is shunted by a choke, and sometimes some residual voltage in the circuit will throw off a resistance reading. Try removing one lead of the resistor and checking again, and if it's OK, see if it is paralleled with another low resistance component.

Stu jaxon

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Apr 6, 2021, 11:55:52 AM4/6/21

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I did lift a lead, and it's still reading zero, like a short.??? it doesn't look like it's paralleled with another low resistance component.

Peter W.

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Apr 6, 2021, 1:31:26 PM4/6/21

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> I have a .068 ohm resistor reading 0.00.. acting like a short, it is a low ohm resistor, is it supposed to read???

Lemme see. 0.068 ohms. Really? That would be within the margin-of-error for many cheap VOMs. Does your meter have a range-adjust? If you are in the 0-10.000 range, you will not get a wiggle at 0.068 ohms. Of you are in the 0-1 ohm range, that is entirely something else.

Peter Wieck
Melrose Park, PA

Ralph Mowery

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Apr 6, 2021, 1:40:06 PM4/6/21

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In article <72fa8efb-5541-4ec0...@googlegroups.com>,
peterw...@gmail.com says...

>
> > I have a .068 ohm resistor reading 0.00.. acting like a short, it is a low ohm resistor, is it supposed to read???
>
> Lemme see. 0.068 ohms. Really? That would be within the margin-of-error for many cheap VOMs. Does your meter have a range-adjust? If you are in the 0-10.000 range, you will not get a wiggle at 0.068 ohms. Of you are in the 0-1 ohm range, that is entirely something else.
>
>
>

It would take a very special meter to show a .068 resistor value. That
or measure the voltage across it with a known ammount of current through
it.

For most meters there could be that much contact resistance.

Cydrome Leader

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Apr 6, 2021, 2:26:07 PM4/6/21

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0.068 ohms is basically a short. It's unlikely a resistor will fail
shorted, so leave it alone, it's probably OK.

jurb...@gmail.com

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Apr 9, 2021, 12:16:43 AM4/9/21

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A 0.068 reading zero is not uncommon. Most ohmmeters do not measure that low. Suffice it to say it is not open, and it is very unlikely to short.

Before changing tht IC, you must find and fix any shorts on the secondary side of the transformer and identify the output pin. It will go straight to the transformers and may have either a cutout around it in the board or a coating of white shit on the board.

Whichever it is, if nothing go with the ohmmeter from the top (+ probably) and find a pin that checks pretty much continuity to that gong to the transformer. Now look around, there will be a diode, resistor and a cap Make sure those components are not open and as they are voltage snubbers without them the IC is destroyed fast.