Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.1 6/24/83; site fortune.UUCP
Path: utzoo!linus!decvax!harpo!ihnp4!fortune!rpw3
From: rpw3@fortune.UUCP
Newsgroups: net.micro.cbm
Subject: Re: wavy screen problem - (nf)
Message-ID: <2250@fortune.UUCP>
Date: Wed, 11-Jan-84 19:20:49 EST
Article-I.D.: fortune.2250
Posted: Wed Jan 11 19:20:49 1984
Date-Received: Fri, 13-Jan-84 04:42:14 EST
Sender: notes@fortune.UUCP
Organization: Fortune Systems, Redwood City, CA
Lines: 22

#R:ihuxr:-83200:fortune:26000001:000:926
fortune!rpw3    Jan 11 16:09:00 1984

Almost without exception, wavy screen = bad regulation in power supply,
either the 64 or the monitor (generally the monitor). What you are
seeing is the tip of a 60Hz power ripple "beating" against a 59.5 (or a
60.5) Hz vertical refresh. The vertical retrace is driven from the
clock crystal of the computer, so it's not locked to the power line.
Every two seconds they get a full cycle out of phase. Suggest trying
someone else's monitor to double-check; if no problem, trash it.

(Cheap black and white TVs often have this problem but don't show it,
since the broadcast guys are VERY careful to stay CLOSE to 60.00 Hz.
Color sets, which generally have somewhat better regulation, are driven
with NTSC's 59.94 Hz, which will roll every 15 seconds or so.)

Rob Warnock

UUCP:	{sri-unix,amd70,hpda,harpo,ihnp4,allegra}!fortune!rpw3
DDD:	(415)595-8444
USPS:	Fortune Systems Corp, 101 Twin Dolphins Drive, Redwood City, CA 94065