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PostPosted: Mon May 17, 2004 15:38 
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Joined: Sat May 08, 2004 21:56
Posts: 4
Location: Bucharest, Romania
Last week I needed help with Powertip PG128128A LCD but nobody bothered to answer for about three days.Anyway, the problem was the contrast voltage which had to be around -12V.So...I made a lightly modified charge pump.It has an output of about -16V from a +5V input, a maximum current of 10mA (beyond this point voltage drops significantly) and fits on a piece of 6*4cm of test board.Anyone having problems with the contrast circuit feel free to use this schematic.R3 is a 10k pot for manual contrast adjustment.
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PostPosted: Tue May 18, 2004 18:03 
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Joined: Sun May 05, 2002 22:05
Posts: 2063
Location: Lappeenranta, Finland
Thanks for the schematic.

mihneavoda wrote:
Last week I needed help with Powertip PG128128A LCD but nobody bothered to answer for about three days.

Did you ask about it in this forum ? I just tried to look around but didn't see anything like that.
Anyway it's not that strange in a forum like this that you won't get answer immediately. I for example haven't had time to be here in the last four days. Sometimes posts can be also missed and then noticed weeks later...
But looks like you solved your problem yourself :)


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 Post subject: -8 Volt up to 2mA
PostPosted: Sun Jun 13, 2004 9:03 
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Joined: Sat Jun 12, 2004 22:38
Posts: 22
Here is a very simple circuit I made up from leftover parts.
Using a SMD RS232 driver and a few CAP form a dead CD-ROM.

The output will drop to 4 volt at 1.5mA, but for my lcd all I need is -3v 1.5mA.

Maybe some one can use it.!!

STEVE


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 Post subject:
PostPosted: Sat Nov 13, 2004 2:58 
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Joined: Wed Nov 10, 2004 8:46
Posts: 21
what is the value of the caps you used?


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 Post subject:
PostPosted: Fri Oct 07, 2005 7:33 
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Joined: Sat Jun 12, 2004 22:38
Posts: 22
2.2uf


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PostPosted: Mon May 23, 2011 12:54 
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Joined: Fri May 20, 2011 12:24
Posts: 2
the scheme is detailed:) it's great
extracting audio from YouTube


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