Message-ID: <28@eneevax.UUCP>
Date: Tue, 1-Nov-83 18:07:02 EST
Article-I.D.: eneevax.28
Posted: Tue Nov  1 18:07:02 1983
Date-Received: Fri, 4-Nov-83 03:17:47 EST
Organization: Univ. of Maryland, EE Dept.
Lines: 30

[This line intentionally left non-blank, to satisy news]

I have had experience with 3 Atari 800 computer exhibiting the
'horizontal bars' problem.  All 3 had begun doing this after
memory was added.  This looked suspiciously like a power supply
problem; the units had passed the factory test with the 16k
originally installed, but were not up to spec with the additional
load of more memory.  

	An oscilloscope on one of the offending units confirmed
that there was oscillation on the +5 and +12 lines, so I got out
my trusty soldering iron, and soldered some high-quality, silvered
mica capacitors across those lines.  They are available at the front
of the computer, under the keyboard.  Usually there are already
some small glass capacitors that look like diodes there.  Leave them,
and parallel any needed capacitance.  It doesn't take many picofarads,
just fast ones.

	This fix totally cured all the computers, maybe it will help
yours.  

				--Sir Spam the Roadie
				  (John Rehwinkel)
				  ...!umcp-cs!eneevax!spam

PS:  My computer, which is dropped/frozen/baked often, never has any
     problems of any sort, the ones that get sick are the ones that
     get the velvet-cushion treatment.  Apparently, Apples need this,
     but the Ataris take umbrage at being treated like unliberated
     women.