Path: utzoo!attcan!uunet!portal!cup.portal.com!RCH
From: RCH@cup.portal.com (Ric C Helton)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Heat problem ???
Message-ID: <13306@cup.portal.com>
Date: 8 Jan 89 04:42:32 GMT
References: <6418@cg-atla.UUCP>
Distribution: na
Organization: The Portal System (TM)
Lines: 34

In reference to the question on the 800XL heating up and flashing
random characters on the screen...  I own an old 800 that no one can figure
out what is wrong with.  I had it serviced by American Technavision
(not a good experience) and they replaced all the RAM chips and
claimed to have it in tip-top shape.  It had been struck by lightning.

Well, the RAM cards had all jarred loose in shipping, so I plugged them
back in (remember that the 800 has multiple boards... XLs and XEs are all on
one board).  It seemed to work fine, but after it had warmed up (say,
about 15-20 minutes) the screen started displaying horizontal rows of
seemingly random characters, then switched graphics modes, and finally
went black all together.  After letting the 800 cool off, I turned it back on.
It worked fine for 10 minutes, then the same thing happened.

Our best guess was that a power transistor was going bad, or that some
screen RAM was bad.  We had it checked and reserviced... They couldn't find
anything wrong.  Then I had an idea.

I asked them what sort of power supply they were using.  They said they had a
special bench power supply that they used to test all equipment.  I was
unable to get any specs on it.  The 800 uses the same power supply that the
1050s and 810s (disk drives) use, with power rating given as 31 VA.  I
was thinking that possibly the overheating power transistor was drawing
more current than the power supply was
rated at, and that the special power supply used at the service place was
capable of delivering more amperage.  But I have been unable to determine 
exactly how much current it would take, or to find a power supply that
was rated at higher than 31 VA (34, maybe? It is a weird rating, according to
a local electronic supply house.)

If you find anything out, and if indeed this is the same problem you are havin
having, let me know what happens via mail.
-Ric          RCH@cup.portal.com
      Freestyle BBS 404/546-8256