lew@ihuxr.UUCP (Lew Mammel, Jr.) (01/10/84)
I got a Commodore 64 for Christmas and I am quite pleased with it. However, I do have a problem which I wish I could correct. The screen image has a wavy appearance. A wave of horizontal displacement, with an amplitude of about 1/2 a character width, traverses the screen from top to bottom with a period of about 2 seconds. This gives the appearance of looking down through water. I checked the grounding, and found good continuity between the ground leads and the wall socket ground. I checked it too and found that it is really grounded to the plumbing. My suspicion is that this wave is being generated internally and being fed to the RF output. Can anybody help me on this? Lew Mammel, Jr. ihnp4!ihuxr!lew
rpw3@fortune.UUCP (01/12/84)
#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 94065glen@intelca.UUCP (Glen Shires) (01/15/84)
One quick fix for wavy screen problems such as that noticed by Lew Mammel
is to simply reverse the AC power cord in the wall outlet.
I believe the c64 has a three-prong plug so it is not advisable to reverse
it, but if the TV/monitor you're using has a two-prong, non-polarized AC power
plug, try unplugging it and turning it around and plugging it in again.
Sometimes it helps tremendously, I don't exactly know why.
I agree with Rob Warnock's assessment the wavy screen problem, which
would suggest that reversing the plug would have no effect. Still, it
does sometimes do the trick.
^ ^
O O
>
\-/ ----mellow
Glen Shiresgrant@hp-pcd.UUCP (grant) (01/21/84)
#R:ihuxr:-83200:hp-kirk:18100002:000:168
hp-kirk!grant Jan 16 09:10:00 1984
Another partial remedy that I have found, is to tweak the horizontal and/or
vertical hold on my TV. It can adjust the wave slightly.
Grant Garner !hp-pcd!grant