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LCD INVERTER: output voltage?

 
 
toddaway
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      10-09-2005, 04:34 PM
I have a blank screen on my laptop, and assumed it was the inverter o
cable so I replaced both with no change. If I suspect the inverter i
bad, shouldn't I be able to get an AC voltage on the output side?
get an indication of 3 or 4 DC volts on the input side of th
inverter, but when I check the two output leads for AC, I ge
nothing. What am I doing wrong....or is it possible I have 2 ba
inverters

 
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mike
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      10-09-2005, 08:43 PM
toddaway wrote:
> I have a blank screen on my laptop, and assumed it was the inverter or
> cable so I replaced both with no change. If I suspect the inverter is
> bad, shouldn't I be able to get an AC voltage on the output side? I
> get an indication of 3 or 4 DC volts on the input side of the
> inverter, but when I check the two output leads for AC, I get
> nothing. What am I doing wrong....or is it possible I have 2 bad
> inverters?
>


What are you checking it with?
If you have a good inverter, you may have created a BAD voltmeter.
An unloaded inverter can have more volts than the max spec on your
voltmeter. YMMV.

Most failures I've seen have been bad backlight. Or the series cap in
the output goes open. Or transformer goes shorted.

Be extremely careful working on the inverter. You can blow up your
instrumentation. And you'll make a very big wet spot on the floor
if you touch the wrong part. Have 911 on speed dial.
mike

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Barry Watzman
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      10-10-2005, 05:29 AM
The output of the inverter is extremely high voltage (over 1,000 volts,
at least when the lamp is starting) and can be LETHAL.

If you are poking around like you apparently are, with relatively little
knowledge of what you are doing (the fact that you ask the question
suggests this), frankly you are lucky that you are still alive and healthy.

The voltage is too high to be measured with the test instruments
availalbe to most users.


toddaway wrote:
> I have a blank screen on my laptop, and assumed it was the inverter or
> cable so I replaced both with no change. If I suspect the inverter is
> bad, shouldn't I be able to get an AC voltage on the output side? I
> get an indication of 3 or 4 DC volts on the input side of the
> inverter, but when I check the two output leads for AC, I get
> nothing. What am I doing wrong....or is it possible I have 2 bad
> inverters?
>

 
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ikenfixit
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      10-10-2005, 06:34 PM
Barrys right.. Dont try to measure the output side with a DV
incapable of at least 1.5KV AC.. (Not many around that are).. Hig
voltage probe is best for this.. Sombody send some Bounty quicke
uppers.. (Inverter is trashed).

 
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toddaway
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      10-10-2005, 07:33 PM
Doh....didn't know it was that high.

But, alas, it's current that kills, not voltage.

Scuffing yer feet across the carpet generates thousands of volts
Deadly current can't get through those itty bitty wires

Anyway, I think my motherboard is bad. I get no output from th
inverter unless I crank on the tv out jack or put pressure on th
components in that area. When I tug on the tv-out, the LCD light
up, but with vertical lines on it. External monitor output work
fine

 
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H. Dziardziel
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      10-11-2005, 01:25 AM
On Sun, 09 Oct 2005 16:34:46 GMT,
(E-Mail Removed)-spam.invalid (toddaway) wrote:

>I have a blank screen on my laptop, and assumed it was the inverter or
>cable so I replaced both with no change. If I suspect the inverter is
>bad, shouldn't I be able to get an AC voltage on the output side? I
>get an indication of 3 or 4 DC volts on the input side of the
>inverter, but when I check the two output leads for AC, I get
>nothing. What am I doing wrong....or is it possible I have 2 bad
>inverters?


A typical DMM measures AC sine waves up to 400Hz limit , a cheap
DIY type just over 60Hz, limit whereas the inverter runs at
40K-100KHz An ordinary analog with an audio db scale may give a
better indication as the meter rectifiers are good to nearly
20KHz, and better ones are reasonably accurate to almost 100KHz.

To get a ballpark idea any small rectifier with a small capacitor
will rectifiy that high frequency. The DC voltage on the
capacitor will be close to the AC peak value, etc. Watch the
loading and voltage of course. A voltage divider off the
capacitor solves the meter range limits.
 
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Barry Watzman
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      10-11-2005, 01:36 AM
Yes, well, it's voltage that makes the lethal current flow.

Your attitude is a bit too casual. This isn't "static electricity". An
LCD inverter can be lethal. It probably won't be most of the time, but
it can be. It's milliamps and [almost always] tens of milliams, not
microamps. And it's also a lot more than most TV set 2nd annode power
supplies.

[The available current range is from perhaps just under 10ma for very
low power single lamp inverters to as much as 80ma. for high-output
4-lamp inverters [not common in a laptop, but my 19" desktop LCD has 4
large lamps, one on each edge of the panel.]


toddaway wrote:

> Doh....didn't know it was that high.
>
> But, alas, it's current that kills, not voltage.
>
> Scuffing yer feet across the carpet generates thousands of volts.
> Deadly current can't get through those itty bitty wires.
>
> Anyway, I think my motherboard is bad. I get no output from the
> inverter unless I crank on the tv out jack or put pressure on the
> components in that area. When I tug on the tv-out, the LCD lights
> up, but with vertical lines on it. External monitor output works
> fine.
>

 
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Gerhard Fiedler
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      10-11-2005, 02:01 PM
Barry Watzman wrote:

> [The available current range is from perhaps just under 10ma for very
> low power single lamp inverters to as much as 80ma. for high-output
> 4-lamp inverters [not common in a laptop, but my 19" desktop LCD has 4
> large lamps, one on each edge of the panel.]


40 mA flowing through your body can be deadly. So a high-voltage generator
that can provide that much is not to be taken lightly.

Gerhard
 
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BillW50
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      10-11-2005, 02:26 PM

"Gerhard Fiedler" <(E-Mail Removed)> wrote in message news:w3sclea86mpp$(E-Mail Removed)...
Date: Tue, 11 Oct 2005 11:01:49 -0300

> Barry Watzman wrote:
>
> > [The available current range is from perhaps just under 10ma for very
> > low power single lamp inverters to as much as 80ma. for high-output
> > 4-lamp inverters [not common in a laptop, but my 19" desktop LCD has 4
> > large lamps, one on each edge of the panel.]

>
> 40 mA flowing through your body can be deadly. So a high-voltage generator
> that can provide that much is not to be taken lightly.
>
> Gerhard


Where did you hear that? As I heard it takes 1000ma (or one amp) to kill
someone.


______________________________________________
Bill (using a Toshiba 2595XDVD & Windows 2000)
-- written and edited within Word 2000

 
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Barry Watzman
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      10-11-2005, 03:40 PM
There isn't agreement on the minumum current required to cause death,
but from the research I've done, 6 ma (.006 amps) through the heart can
cause VFib (fatally abnormal heartbeat) resulting (indirectly, but
quickly) in death. Various reports indicate that this can be achieved
with as little as 30ma throught the body, although more commonly a
higher current (60 to 80ma) is encountered before shocks are commonly
considered to be lethal.


Gerhard Fiedler wrote:

> Barry Watzman wrote:
>
>
>>[The available current range is from perhaps just under 10ma for very
>>low power single lamp inverters to as much as 80ma. for high-output
>>4-lamp inverters [not common in a laptop, but my 19" desktop LCD has 4
>>large lamps, one on each edge of the panel.]

>
>
> 40 mA flowing through your body can be deadly. So a high-voltage generator
> that can provide that much is not to be taken lightly.
>
> Gerhard

 
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