CDH@MTUS5.BITNET (05/03/91)
Hello...It seems I have a slight problem with my Amiga.
Its dead.
I was wondering if anyone out there in Netland might have an
idea what is not working anymore.
Machine:
Amiga 2000, Rev 4.3 motherboard
1M Agnes, Supra 8-up (with 2M), IVS Trumpcard
Problem/Symptoms:
A diode was burned out on the motherboard (actually burned clean
through). It was replacd (1N4001) located near the power supply
input to the motherboard. It was either D600, or D900 (I forget).
A technician at the company that sells the Megachip said the revision
motherboard I have is missing a capacitor which is needed for the
Megachip board to work. I still have yet to put this capacitor in.
This capacitor is located near the Agnes chip.
Machine refuses to boot.
White screen on power up (with *no* boards in machine, no floppy
in drive). Goes through gray colors, but when it should come up
with a work bench prompt, stays white instead.
Floppy drive clicks like it is waiting for a disk.
When disk is inserted, floppy stops clicking, however, access light
does not come on drive and drive does not spin.
With the Trumpcard in, the machine will attempt to Autoboot off
the hard drive. It usually does not succeed. The background color
*does* change from white to blue (which is my boot background color).
A couple powerup attempts let to a screen of garbage (kinda looked
like page zero), with moving bits on the screen. Once or twice the
machine actually booted to the point where I could type a command and
it would access the disk. The machine usually died pretty quickly.
Most of my attempts at booting, however, ended up with the machine
just stopping before it finished booting.
We tried using a logic probe, but everything looked "normal" as far
as we could tell. ie: yup, there was power to memory, chips, etc
Ok, I'm a CS major and my friend is a EE (both undergrads).
Suspected Killers:
Megachip 2000 (The board for about $350 which allows you
to put a 2M Agnes in the 2000)
Supra 8-up (Either the Megachip, or the Megachip in
combination with this board)
How it happened (I think):
The roommate purchased this board originally for his machine,
but had to send his motherboard in for replacement since it
was a revision 6 and would not work with the Megachip.
While his machine was gone, I became interested in possibly
having a 2M board in my machine :)
So: I pulled my machine completely apart (motherboard too)
so I could get that darn original Agnes out of its socket.
I had to use the holes on the bottom as well as the chip
puller to pry that sucker from its wedge. Its highly
possible that I damaged the Agnes socket while pulling
the chip (I am leaning toward that idea now).
I put the new Agnes board in, and put the machine all back
together.
It worked beautifully (2M chip, 2M fast - Supra) for about an
hour. I then began to notice a flash occasionally. At first
I thought it might be power or the monitor acting up (dorms).
The longer I left the machine on, the worse the flicker got.
If I powered my Amiga off, then back on the flicker would go
away for a while, but always return faster than previously.
I pulled the Supra and Trumpcard out and the problem went
away. I then put the Trumpcard back in and the problem still
did not return. I assume there must have been some conflict
between the Supra and the Megachip.
I let the machine run for a whole day without the Supra board
and it did not give incident. I then put the Supra back in.
The problem did not come back immediately.
Then I did the foolish thing. I turned the monitor off and
let the machine sit for a day (I usually leave my machine on
24 hours a day). When I came back the next day, the screen
was blank (border color). I cycled power and the machine came
back on for a few seconds and then quit. I tried again;
same result.
At this point, I pulled my machine all apart and removed the
Megachip. I replaced the original Agnes back into its socket.
When I reassembled the machine, the screen did not return!
I tried pulling and reinserting Agnes; to no avail.
What I have already tried:
Replacing the diode that was burned clean through.
Swapping every pullable chip on the motherboard
[68000, Agnes, Paula, Denise, Gary, ROM, the two 6820
chips, etc].
Probing around randomly with a logic probe.
Hooking the machine up to a composite monitor to see if it was
my RGB section. Exactly same results.
Anyone with any ideas or suggestions, please help.
Thanks (in advance).
--desperate college student here in need of an Amiga :(
- Chris Hooper Computing Technology Services Consultant
cdh@mtu.edu Michigan Technological University
Also: cdh@mtus5.mtu.edu CDH@MTUS5.Bitnet and cdhooper@symmetry.cs.mtu.edu