Newsgroups: comp.sys.amiga.hardware
Subject: A3000: Heating up?
From: analogki@qed.cts.com (Jeff Robertson)
Date: 1 Sep 92 21:26:09 GMT
Organization: The QED BBS, Lakewood CA


I have an Amiga 3000 (25Mhz) with 52meg Quantum HD, two internal floppy
drives, 2megs of CHIP RAM and 4megs of FAST RAM. My mom-board rev# is 8.9.

It occurred to me one day that my power supply's fan shouldn't be BLOWING
air INTO the machine, as every power supply I have ever seen on a 3000 was
SUCKING air OUT! The same is true for every other power supply for any
computer I have ever seen. Makes sense, too. Sucking air OUT of the machine
seems more efficient in cooling than forcing it in. This action also keeps
DUST from piling up on the IC's.

So, seeing as how I bought the machine used and it was clearly out of
warranty, I decided it was simple enough for me to remove the power supply
and reverse the air-flow myself. I did so successfully and also took
advantage of the opportunity to do some much needed dusting. The innards of
the power supply and a good part of the motherboard were filthy!

I got the machine back together and running in no time. Later that day, I
started noticing funny things concerning graphics -- programs that had
colorful gadgets, etc. were appearing SCRAMBLED on the screen. Other things
were acting funny, too. My song modules were being unrecognized by their
players (resulting in GURU's), wouldn't load at all or if they did manage
to load, played incoherently. Programs that opened standard console windows
couldn't get it done -- they'd open, then close; locking up the machine or
GURU'ing.

All these funny things were happening as I was trying out a new hard drive
on my system. It was a hard drive KNOWN to be buggy with the A3000 -- the
Quantum 240LPS. So, I made the connection between programs not loading
properly to the new drive. I figured I had two strikes against me: 1) I was
told by a tech that "older" A3000 motherboard's SCSI controllers had
trouble dealing with NEWER SCSI devices (i.e. ones that used a 14MHz clock
speed [SCSI II ?!?]) and 2) The Quantum 240LPS with a ROM rev of 4.6 was
said to be bug-ridden. Either of these things must have had SOMETHING to do
with what was going wrong!! (I thought).

This didn't make any sense because the problem(s) seemed to affect my OTHER
drive (the 52meg Quantum) as well. I came up with another thought that
maybe the Q240 was just "interfering" with SCSI buss operations. This idea
was backed up by another curiosity I discovered -- my 52meg drive, the
first in the chain, was coming up with a device number of 1 even though it
was hardwired for 6. Strange!  (yes, I had my terminators in the right
places).

Something else I should mention is that during all this troubleshooting (it
went on for days, maybe weeks) the ambient room temperature was around
85-90ish degrees F. I work in a hellish environment sometimes! To test to
see if heat had anything to do with the system failures, I removed the
cover from 3000 and placed a small muffin fan, blowing air across the
motherboard from the right side to the left, concentrating the flow on the
hot spots. This may or may not have lowered the frequency of the strange
occurrences --  just couldn't say for sure.

Some time later, I sold off my Q240 drive. I wanted to save up for the
Tower version of the 3000 that already comes with a nice, 200meg+ Quantum
(pre-bugginess, I might add). I could no longer attribute any of my
problems to the addition of the new drive on the system. I was back to my
original setup!

The system-funniness didn't go away! The weather conditions were becoming
more favorable, though, and I didn't have to use my air-conditioner at all.
I still kept a fan blowing over the machine, however, and I the frequency of
the random silliness dropped even more. I tried running every piece of
system diagnostic software I could find in hopes of stumbling across some
clue to what was going on. No help!

Then, one day as I was fiddling with the "avail" command, I noticed
something incredibly strange about my chip RAM. Avail said I had chip RAM
available in the billions range. Hahah! I starting inspecting chip RAM info
with other system utilities. "SysInfo" would sometimes CRASH and lockup the
machine when it got to the CHIP RAM page. "AmigaRealTimeMonitor" would give
me the same strange readings Avail did. I thought, "okay, maybe there's
something wrong with my FAT AGNUS or maybe the chip RAM itself is bad!"

Ahh, but, the problems would come and go. Sometimes I could go a whole day
with anything funny happening. One thing I did notice, though. The problems
never occurred within the first 15-30 minutes of CPU use (after powering up
in the morning). I continued to work on HEAT build-up being the cause. I
would position my fan to cool certain areas of the motherboard only. Most
of the time, I had the fan on the left side of the daughterboard "barrier",
where the chip ram and Fat Agnus are located. I hit peak room temp one day
(even though its mild outside, my room feels like a greenhouse sometimes)
and simultaneously, failures concerning chip RAM cropped up again. Was my
fan helping?   Maybe...
 
To make a long story even longer, I had to finally convince myself that
maybe I should have left the fan where it was! Perhaps forcing air IN was
better in cooling in the case of *my* 3000. And, ya know, one of the OTHER,
more heat-sensitive chips is directly in the path of air flow with the fan
in its original position -- the 68030!!

I am going to switch the fan back, right now! If this doesn't end the
funniness once and for all, I just don't know what to think. Luckily, I
haven't lost any data over these lock-ups, but I don't want deal with it
anymore.

Comments? Suggestions? Please share them.

(Thanks for reading my long story).



------------------------------
analogki@qed.cts.com (Jeff Robertson)  or  qed!analogki
The QED BBS -- (310)420-9327
Newsgroups: comp.sys.amiga.hardware