From: haroldt@orion.yorku.ca
Subject: Re:  More info about my troublesome 3b1
Organization: York University
Distribution: na
Date: Fri, 11 Sep 1992 15:31:44 GMT

Greetings:

  (Disclaimer:  What follows is an opinion.)

In article <1992Sep10.214017.1066@umbc3.umbc.edu>, hybl@umbc4.umbc.edu (Dr. Albert Hybl (UMAB-BIOPHYS)) writes:

[...stuff deleted...]
> Without closing the machine, I reattached the keyboard and turned
> the 3b1 on.  Two pencils separate the keyboard from the
> metal platform where it would usually be when packed.
> The monitor faces the ceiling with space allowed for
> the fan to function.  THE MACHINE BOOTED AND HAS BEEN
> RUNNING SINCE--ABOUT 40 CONTINUOUS HOURS SO FAR.  I have run
> a number a tasks on the machine, including I/O via the floppy
> drive.  I'll start running the diagnostic disk to test the
> memory soon.

  I would not recommend that you run the machine open without some
modification.  See below.

> The metal plate below the keyboard is running warm.  The CPU
> is surely just as hot as when the hood is closed.  The fan

  I've found otherwise.  I ran my unit open for a while, noticed the 
intence heat and decided to study it's cooling system.  The case
is designed in such a way as to cool the top metal plate quickly 
thus cooling the cpu and memory.  If you are going to run it open
(which I now do) make one modification... get a bigger fan!

  My 3B1 is now mounted vertically inside a small stereo stand with
a $10 125V (self powered, not drawing from the already underpowered 
3B1) fan.  The fan blows accross the disk drive and power supply (on
the bottom of the stand), and up past the cpu and memory.  The top 
metal plate is removed.  

  To convince myself that this was a good idea, I left the 3B1's fan
connected for a while.  It never hit high speed.  Incidently,  I was
having two problems that were thermally related.  The first was that
every time the fan would change speeds, the drive would as well by
enough to cause an error.  The other problem was that after a couple of
days the box would just lock up.  Neither problem occurs now.  The 
stock fan is not being used which frees up just a bit more juice for
the rest of the unit.

> seems to be working well and there was no indications of
> overheating when the shell was closed.  This suggests that
> it is probably not a temperature-sensitive problem.  It may
> be related to a crimped cable or poor grounding.

  I would agree.  The 3B1 has a thermal switch for the fan so 
you would notice the fan running at full speed before any thermal
problems occur.  I'm contemplating connecting the thermal switch to 
some indicator or perhaps software that can shut the box down if the 
temperature stays up too long.  Any ideas?

> The loose ground wire must have been like using a two prong
> adaptor plug to defeat the grounding prong.  COULD or DOES
> POOR GROUNDING CAUSE PANIC PROBLEMS?  COULD INTERMITTENT
> CONTACT BETWEEN COMPUTER AND GROUND CAUSE PROBLEMS?

  Any time that wire connects or disconnects, there will be a small
change in Voltage and a definate change in the overall Capacitance.
In other words, Yes.

Xref: sparky comp.sys.3b1:3294 comp.sys.apollo:3481 comp.sys.atari.st:13327 comp.sys.sequent:536 comp.unix.aix:9424 comp.unix.amiga:2095 comp.unix.cray:262 comp.unix.sysv386:14138 comp.unix.ultrix:6725