Vizio L30WGU help


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Vizio L30WGU help

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skir0987
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Jun 14, 2012, 8:34 PM

Post #1 of 4 (1602 views)
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Vizio L30WGU help	Can't Post

Hi,
I have a Vizio L30WGU TV that is broken. It turns on and flashes the backlight for about a quarter of a second and then stays on but no backlight. I assumed it was an inverter issue, but replacing the inverter board did not help. I also tried replacing the main board and power board, but nothing has worked. The only board left to replace is the LCD controller board, but I think it's very unlikely to be that board because if I shine a light onto the screen I can still navigate menus and such.

Can anyone help me diagnose my problem? The only thing I can think of at this point is that either the new boards somehow got fried by something else or that the backlight itself is dead (but it still does flash).

Thanks,
Shep

jts1957
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Jun 14, 2012, 9:36 PM

Post #2 of 4 (1598 views)
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Re: [skir0987] Vizio L30WGU help [In reply to]	Can't Post

Substitute the panel (IF you can obtain one).

Bad CCFL probably.

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Location: Far, Far Away

skir0987
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Jun 14, 2012, 10:30 PM

Post #3 of 4 (1590 views)
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Re: [jts1957] Vizio L30WGU help [In reply to]	Can't Post

Alright, thanks for the quick response. I assume this must be the issue too--although there are other funky things going on. I was probing the inverter board with my multimeter and I noticed it's getting 24V in on each rail from the power supply (normal) but nothing is coming out of the transformers. When the display flickers they jump to their normal voltage but then quickly drop back to zero. Does this symptom fit the broken panel diagnostic?

Thanks

jts1957
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Jun 14, 2012, 11:19 PM

Post #4 of 4 (1588 views)
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Re: [skir0987] Vizio L30WGU help [In reply to]	Can't Post

If Inverter board has B-Plus & an "enable" voltage that comes up (and stays up) when the set is turned "on," then it must be one of the following:

Bad solder joint(s) on Inverter board - sometimes will "char" board
Burnt/charred connectors, resistors or capacitors
Drive to transformer is defective - swap Inverter board with a "Known Good" one.
Transformer is defective - compare one to another - primary to primary / secondary to secondary. (Swap board with a "Known Good" one)
one or more CCFL bulbs are defective - They can get "blackened" ends, physically break the wiring or the glass bulb itself - Visual exam - requires disassembly of the panel in most cases.

Remember the inverter is a "balanced" circuit. It monitors the condition of each CCFL bulbs driving circuitry and can shut the whole board down if even only one item is defective.

If you have a scope you can hold probe close to each transformer (one at a time) as you cycle the set on.

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Location: Far, Far Away

(This post was edited by jts1957 on Jun 14, 2012, 11:21 PM)

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