[ltp] My T22 backlight has died - how do I fix it?
Bert Haskins
linux-thinkpad@linux-thinkpad.org
Thu, 25 Aug 2005 13:36:51 -0400
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Javier (a.k.a AlBundy) wrote:
>On 8/25/05, Bert Haskins <bhaskins@chartermi.net> wrote:
>
>
>>Every Thinkpad ( 600x 770xy 390s, A2xx series, A3xx ) that I've ever
>>worked on has used a CCFL tube.
>>
>>
>[...]
>
>
>>I do check the inverter first though.
>>I use an inverter that I keep for just this purpose and if the screen
>>does light up I debug the other circuits.
>>My test inverter runs on it's own power ( battery ) so it's not affected
>>by other problems.
>>
>>////// start rant /////
>>One thing that I don't like about the newer machines is that just about
>>everything is built on the
>>motherboard including !@#$CUSS%$%& the DC/DC converter !@#$CUSS$%%%.
>>////// end rant ////////
>>
>>
>
>Question:
>
> inverter == DC/DC converter?
>
The term inverter is a old fossil ( like me ) from the days when they
were used to generate a
negative grid bias for high-power vacuum tube circuits.
Hence the term invert...er
Slamming quickly back to Thinkpads the DC/DC converter is a quite
complex unit(s) which now
seems to be on the motherboard ( IMHO bad engineering, see rant ) or on
a separate circuit board.
It serves to convert the power from the battery and/or the ac adapter to
the voltages needed by
the computer and battery.
>or
> inverter == DC/AC converter?
>
>
The inverter ( found on the lcd section... upper half ) takes the power
from the DC/DC converter
and steps it up to about 220 volts @ about 400 cycles.
This will be different for different models of laptops and different LCDS.
There is a capacitor on the output end of the inverter which is used to
tune and smooth the output.
This cap has BEEN the problem on a few machines that I have dealt with.
Please notice that there is no 'inverting' going on here.
>
>PS: It should be great if you could take photographs of inverter and
>CCFL tubes, and put them in thinkwiki.
>
You know, I would do this for information purposes only.
In fact if I was still teaching industrial service techs, I think that I
would use this repair
as sort of a masters thesis.
It aint easy and you sure as higher taxes could never make a dime doing it.
love this NG...
Bert
>
>-----------
>AlBundy
>
>
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Javier (a.k.a AlBundy) wrote:<br>
<blockquote type="cite"
cite="midf31cece105082509294c6020f2@mail.gmail.com">
<pre wrap="">On 8/25/05, Bert Haskins <a class="moz-txt-link-rfc2396E" href="mailto:bhaskins@chartermi.net"><bhaskins@chartermi.net></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Every Thinkpad ( 600x 770xy 390s, A2xx series, A3xx ) that I've ever
worked on has used a CCFL tube.
</pre>
</blockquote>
<pre wrap=""><!---->[...]
</pre>
<blockquote type="cite">
<pre wrap="">I do check the inverter first though.
I use an inverter that I keep for just this purpose and if the screen
does light up I debug the other circuits.
My test inverter runs on it's own power ( battery ) so it's not affected
by other problems.
////// start rant /////
One thing that I don't like about the newer machines is that just about
everything is built on the
motherboard including !@#$CUSS%$%& the DC/DC converter !@#$CUSS$%%%.
////// end rant ////////
</pre>
</blockquote>
<pre wrap=""><!---->
Question:
inverter == DC/DC converter?</pre>
</blockquote>
The term inverter is a old fossil ( like me ) from the days when they
were used to generate a<br>
negative grid bias for high-power vacuum tube circuits.<br>
Hence the term invert...er<br>
Slamming quickly back to Thinkpads the DC/DC converter is a quite
complex unit(s) which now<br>
seems to be on the motherboard ( IMHO bad engineering, see rant ) or on
a separate circuit board.<br>
It serves to convert the power from the battery and/or the ac adapter
to the voltages needed by<br>
the computer and battery.<br>
<br>
<blockquote type="cite"
cite="midf31cece105082509294c6020f2@mail.gmail.com">
<pre wrap="">
or
inverter == DC/AC converter?
</pre>
</blockquote>
The inverter ( found on the lcd section... upper half ) takes the power
from the DC/DC converter<br>
and steps it up to about 220 volts @ about 400 cycles.<br>
This will be different for different models of laptops and different
LCDS.<br>
There is a capacitor on the output end of the inverter which is used to
tune and smooth the output.<br>
This cap has BEEN the problem on a few machines that I have dealt with.<br>
<br>
Please notice that there is no 'inverting' going on here.<br>
<blockquote type="cite"
cite="midf31cece105082509294c6020f2@mail.gmail.com">
<pre wrap="">
PS: It should be great if you could take photographs of inverter and
CCFL tubes, and put them in thinkwiki.</pre>
</blockquote>
You know, I would do this for information purposes only.<br>
In fact if I was still teaching industrial service techs, I think that
I would use this repair<br>
as sort of a masters thesis.<br>
It aint easy and you sure as higher taxes could never make a dime doing
it.<br>
love this NG...<br>
Bert <br>
<blockquote type="cite"
cite="midf31cece105082509294c6020f2@mail.gmail.com">
<pre wrap="">
-----------
AlBundy
</pre>
</blockquote>
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