Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!pyrdc!gmu90x!jbaker
From: jbaker@gmu90x.gmu.edu (jbaker)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Help with Super Agnus
Summary: Installing the super agnus
Keywords: amiga 2000 super agnus
Message-ID: <2621@gmu90x.gmu.edu>
Date: 20 Mar 90 06:52:55 GMT
References: <2602B7E8.3D54@deimos.cis.ksu.edu= <260471CC.505F@deimos.cis.ksu.edu>
Reply-To: jbaker@gmu90x.UUCP (John Baker)
Organization: George Mason University, Fairfax, Va.
Lines: 67

In article <260471CC.505F@deimos.cis.ksu.edu> jwb@ksuvax1.cis.ksu.edu (Jeff W. Brogden) writes:
>=I just had the new super agnus chip installed in my A2000.  Since then I have
>=been experiencing numerous problems.  The most severe is that my floppy disk
>=drives are almost unusable.  I am now plagued with read/write errors, bad
...
>Question is, how can "avail" show there is more than 512K chip RAM but the 
>OS not know that the Super Agnus exists?  Is this why I am getting all the
>garbage on the screen, etc.?

It sounds like they did a poor installation job.  If you paid to have it done,
you should bring it back and make them fix it.  However, if you want to risk
playing around yourself, I have some suggestions.  (For 2000s only!)

First, open up the Amiga and remove the power supply/drives assembly.
Disconnect cables as necessary and note their orientation.  Now examine
the super agnus (the square chip).  If you see no bent pins, try pushing
it in firmly.  Hopefully it will be loose and this will correct the problem.
While you are in there, push in all the socketed chips.  I usually "ground"
myself before touching electronic parts by touching a large metal object.

Now check the two jumper modifications necessary when installing a "fatter
agnus."  From what you said, it sounds quite possible one was not done
properly.  First, look at jumper J101.  This jumper consists of three pins
and a jumper, which must be on the left two pins for the fatter agnus:
        Old agnus (512K):  o  o--o   Fatter agnus (1M):  o--o  o
(This is looking from the front of the Amiga.)

Now look for jumper J500.  This is simply two pads, no wires.  In Amiga 2000s
with a 512K agnus, there is a trace connecting the two pads.  This is cut
when installing a fatter agnus.  Use a blade to be sure that the trace has
indeed been completely cut, but DO NOT slip and cut any other traces.  I
usually overdo such things, but it is quite possible to not cut it well
enough.

Now carefully put everything back together, double checking all connections,
and be sure that nothing is backwards or forgotten.  It is easy to put the
disk drive connector back onto the motherboard offset by a pin.  Check this.
Be sure to push the connectors onto any internal drives.  These usually get
loose when working inside the computer.

Now cross your fingers, and turn on the power.

By the way, if anyone is putting in their own fatter agnus, a common trick
to get the old agnus out is to super glue a large nut to the top of the chip,
wait a few secs, then screw in a bolt just until it makes contact with the
chip, and pull the chip out.  Try not to rock it (too much).  Mine came
straight out with steady but firm pressure, while holding the socket down
with the other hand.

It also doesn't hurt to carefully remove some of that dust.  You never know
if a little bit of metal might be there somewhere.  I use a small plastic
vaccum cleaner.

WARNING!  WARNING!  WARNING!
If you do anything wrong, make a mistake, or just have bad luck, you could
RUIN your amiga.  In fact, what I have said above might be all wrong and
blow everything up, so don't blame me if anything goes wrong.  I suggest
that if you do anything I say, double check it with other sources.

By the way, if you are looking for a fatter agnus, I got mine from
MEMORY WORLD at (215) 741-6225 at AmiExpo in Washington for $89.00;
the mail-order price may be different.  They also have 1.3 ROMs.

 
John Baker
jbaker@gmuvax.gmu.edu
(703) 941-6840