[net.micro.atari] Troubleshooting Advice

bob@harpo.UUCP (06/03/83)

#N:harpo:25900001:000:792
harpo!bob    Jun  3 11:10:00 1983

My Atari 800 has developed a problem. It is used with a TV as opposed to
a monitor , and the problem exists when all peripherals are disconnected
and unplugged.  Bars of video distortion and noise (horizontal) drift slowly
thru the screen at a steady rate.  The bars (only one at a time) occupy
about 1/5 of the screen, and the remainder of the screen looks less sharp
than usual.  Inserting  and removing  a program ROM a few times seems
to clear up the problem, but
the next time the computer is turned on, it is likely to be back. Looks like
an interference problem to me , as I get the same results on another tv.
Is my modulator dying?  Bad grounding somewhere?  Has anyone else encountered
a similar problem?
						R. L. Carroll
						Bell Labs
						201-386-2609
						Whippany, N.J

rasp@bmcg.UUCP (06/13/83)

I have heard of others with the same trouble,  a  wavy  line
walking  up  the  screen,  so I'll broadcast an answer.  The
problem seems to be a "retrace snake".  This would be caused
if  the ATARI were superimposing 60Hz onto the video signal.
You might note that the frequency exhibited by  the  "snake"
is  that  of  the difference between 60Hz line frequency and
the vertical refresh rate which is quite close.

Look for any source of 60Hz. Bad grounding  is  certainly  a
candidate;  but,  the  most likely culprit is something gone
bad in the ATARI's power supply. If you have access  to  the
appropriate  tools,  check for either a bad rectifier, a bad
filter cap, or a bad regulator. If you're  lucky,  there  is
even  the  possibility  that the problem is as simple as the
end of the video cable that is plugged in  INSIDE  the  case
has partially worked loose and needs only to be reseated.

Please let me know how you make out.

Ron Perloff
Burroughs Corp
16464 Via Esprillo
San Diego, CA 92128
619-451-4519

padpowell@wateng.UUCP (PAD Powell[Admin]) (06/15/83)

his high voltage supply.  If you don't know what you are doing, leave
it alone!  The usual penalty for ignorance is death, or at least
a whopping good shock