Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!ub!uhura.cc.rochester.edu!afry
From: afry@uhura.cc.rochester.edu (Alan R. Fry)
Newsgroups: comp.sys.mac.hardware
Subject: Re: SE/30 screen flickers/no it doesn't/yes it does/...
Summary: It's the hard disk
Message-ID: <14394@ur-cc.UUCP>
Date: 7 Jun 91 16:41:09 GMT
References: <12163@skye.cs.ed.ac.uk>
Organization: University of Rochester, Rochester NY
Lines: 53

In article <12163@skye.cs.ed.ac.uk:> nick@lfcs.ed.ac.uk writes:
:>Any other SE/30 owners had the following problem? A sporadic flickering/jumping
:>of the screen: the top and bottom few pixel rows of the screen suddenly
:>stretch, and the stretched regions drift inward toward the centre and then
:>out again.
:>
:>Reason I ask is that my machine has been doing this, off and on, for months.
:>It's been in for fixing three times, this last time for over a week, and
:>the engineers can't reproduce the problem. When I get it back I expect it'll
:>behave for a few weeks and then start doing it again.
:>
:>The problem seems to be brought on by (internal) HD activity - might it be
:>something to do with the power supply and/or my mains supply? I'll try a
:>line conditioner to see if this has any effect.
:>
:>Just wanted to mention it in case anybody else has seen this symptom and can
:>tell me it's not all in my imagination...
:>
:>	Nick.
:>

I had this very same problem when I installed a 105 meg quantum in my
SE/30.  The disk access flickering was very reproducible in my case, and
damn annoying.  I took it in to the idiot who installed it, and he
'figgered' it was something wrong with the hd.  I didn't buy it, so I called
the company that sold it to me, and they didn't know what the problem was
either, so I called another company.  I finally found someone who knew what
the hell he was talking about, and he explained that in certain SE/30's,
stray magnetic and electric fields from the hd can interfere with the video
card for the built in monitor.  He wasn't sure just what the cause was, but
he thought it was probably the fault of the unshielded video card.  

Anyway, his suggestion was to take the drive and rotate it 180 degrees in
the mount, so that you have to run the scsi cable underneath the drive to
attach to the logic board.  I asked the Certified Idiot Apple Dealer to do
so for me, and he said that he didn't think it was possible, so I took it to
another dealer who promptly did so.  It worked!!  The flickering was almost
entirely gone.  There is still a tiny bit (on the lower right hand side of
the screen), but it is pretty unnoticable, and much better than before.

From the description of your problem, it might be worth trying, just to see
if it becomes any better or worse.  I have heard of people trying to shield
either the drive or the video card with sheet metal (aluminum foil doesn't
seem to work), but I'm not sure if I'd recommend that.

Good luck, and let me know how it goes,

Alan
-- 
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  Alan R Fry                     |    You know what I hate?    
  afry@uhura.cc.rochester.edu    |    Rhetorical questions     
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