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From: janh@hplsla.HP.COM (Jan Hofland)
Newsgroups: comp.sys.cbm
Subject: Re: GEOS and composite video
Message-ID: <960002@hplsla.HP.COM>
Date: Wed, 10-Dec-86 11:55:38 EST
Article-I.D.: hplsla.960002
Posted: Wed Dec 10 11:55:38 1986
Date-Received: Mon, 15-Dec-86 04:21:58 EST
References: <4073@columbia.UUCP>
Organization: HP Lake Stevens
Lines: 21


[]
I, too, have found the composite video text display marginal when using
GEOS.  My solution turned out to be a hardware modification to the C64.
My machine is an early version (version 1, I think).  I noticed that the
more recent vintages use video interface circuits built into the RF
modulator, rather than the transistors, resistors, and capacitor circuitry
mounted directly on the pc board.  What I did was to build a circuit 
that goes between the VicII chip and the DIN video output connector that
duplicates what is happening inside the newer version RF modulator.  The
most significant differences are the use of a locally regulated power
source and separate emitter followers for the composite video, lumenance,
and chroma outputs.  

Jan Hofland
Hewlett Packard
Lake Stevens Instrument Division
8600 Soper Hill Road
Everett, Wa. 98205

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