Path: utzoo!attcan!uunet!zephyr.ens.tek.com!tekgen!stephenc
From: stephenc@tekgen.BV.TEK.COM (Stephen Coan)
Newsgroups: comp.sys.cbm
Subject: Re: HELP! TTL Monochrome on C128D?? Yes? No? Maybe?
Summary: Re: HELP! TTl Monochrome on C128D?? Yes? No? Maybe?
Message-ID: <5493@tekgen.BV.TEK.COM>
Date: 13 Feb 90 16:10:41 GMT
References: <15490001@hpdml93.HP.COM>
Organization: Tektronix Inc., Beaverton, Or.
Lines: 37

In article <15490001@hpdml93.HP.COM>, mfox@hpdml93.HP.COM (Martin Fox) writes:
> I recently purchased a used C128D at a conveniently low price (dirt cheap).
> A friend has decided to upgrade to color on his IBM PC, and has an
> extra green-screen monochrome TTL monitor that he'll let me use.
> 
> So, is there any way I can hook his TTL monitor to my C128D's RGBI port to
> get an 80-column display? The monitor has a nine-pin IBM-compatible plug which
> appears to have the same pin arrangement as my RGBI port, but plugging it in
> directly doesn't work worth diddly. As I can't seem to find any useful
> information about my RGBI port, I am having difficulty figuring out what the
> heck could be the matter.
> 
.
.
> 
> Martin Fox

When I first attempted to get a monitor for my C128, I also had the same
problem.  Well, it turns out that the IBM monochrome raster scan rate is
about 18.3KHz.  The Commodore, to be compatible with NTSC, is at 15.7KHz.
This is a difference of close to 17%.  I took my C-128 to the monitor 
dealer and with his permission, tried a number of his different monitors
on the system.  Only two out of 5 he carried would sync properly to the
C-128.  It turns out that some of the monitors cannot change their scan
rates enough to sync with NTSC.  That is probably the problem you are now
seeing. 

I ended up with an Amdek 301A monitor and it has worked fine for me.  I 
did have to adjust the horizontal and vertical gains/size controls to get
a full screen with the C-128.  I hope that this helps answer this question.


-- 

			Steve Coan
			tektronix!tekgen!stephenc
			(503) 627-1794