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ExpanBlues
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2007-12-01
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SOLVING EXPANSION DEVICE PROBLEMS
By Brian Jean
Ed. note: This is a good article from the US about a problem some Amigas
have with PAL chips - if you think you may have such a problem, try one
of the COMMCARE service shops. I think one of the TV consumer shows was
thinking of making an issue of this.
An Amiga hardware problem has been identified in recent weeks. The problem
is by no means terminal. Your Amiga can recover. The problem affects many
Amiga users who are now using, or who have future plans of using the Amiga
expansion bus. The expansion bus is the 86 pin edge card connector on the
right side of your Amiga. This expansion bus is used to add hardware
devices such as expanded RAM, and hard drives.
Ed Lippert of C Ltd. has explained ...
"Our experience in dealing with customers and dealers
leads us to believe the following:
5-10% of ALL Amigas now in the field WILL NOT
WORK consistently with ONE expansion
device.
25-35% WILL NOT WORK consistently with TWO
expansion devices.
75-85% WILL NOT WORK consistently with THREE
expansion devices.
99% WILL NOT WORK consistently with FOUR
expansion devices."
The big question as an Amiga owner is now "How do I know what percentile my
Amiga falls in?". The answer is not real simple. At this time there is not
an easy way to figure out if your machine has this problem, other than
connecting a bunch of expansion devices to your Amiga and crossing your
fingers. This approach to the problem is not always feasible. Most users do
not, as of yet, own expansion devices to test their machines. However,
if you do have access to expansion devices, here are some symptoms to be
looking for.
1) The Amiga fails to recognize one or more
expansion device connected to the bus; however,
you know the device is in perfect working condition.
2) The Amiga crashes during the boot-up process, not
always in the same place.
3) The Amiga crashes all the way back to KickStart.
This is an almost SURE sign of the problem in your
machine.
The higher number of expansion devices riding on the
expansion bus increases the odds of a problem.
I personally was experiencing a crash during the startup-
sequence that occured most often during the LoadWB command
when my CSA Turbo Amiga 68020/881 was installed under
workbench v1.2. Workbench v1.1 worked fine as long as I did
not use any slide bars. Use of a slide bar caused a GURU
everytime.
Thus far I have been referencing the problem as just that, "THE PROBLEM".
But what exactly is "THE PROBLEM"?
The actual physical problem that Amy is experiencing, is caused by the
speed of the PAL chips used by Commodore-Amiga. Early models used PALs
manufactured by MMI. These PALs seem to work fine (for the most part), but
somewhere down the road, C-A started using TI (Texas Instraments) PALs. The
TI PALs have the same rating as the MMI, but just don't perform as well. It
is not safe to assume that ALL machines with TI PALs will cause system
problems with expansion devices attached, just as it is not safe to assume
that ALL machines with the MMI PALs will be fine. I have MMI chips in my
machine and have experienced "THE PROBLEM".
Through extensive research, C Ltd. has stated they know how to fix Amy.
There are actually two ways of completing this fix. The first is available
now, the second will be available in a few weeks.
FIX #1:
The first method of fixing Amy is to replace two of the four slower rated
'A' PALs with the faster 'B' rated PALs. C Ltd. has permission from
Commodore to reproduce the needed code on the faster PALs and distribute to
those who need them. The PAL update IS NOT available directly from
Commodore. The cost for the new chips is $20.00, plus $3.50 shipping and
handling.
WARNING: THE SURGEON GENERAL HAS DETERMINED THAT CHANGING THE PALs YOURSELF
CAN BE HAZARDOUS TO AMY'S HEALTH!
Making the fix yourself can be VERY tricky. If you do not have experience
working on multi-layer circuit boards, THEN DON'T TRY IT! If you have the
experience, or want to give it a try anyway, here's a few helpful hints.
NOTE: The AUTHOR of this article DOES NOT accept ANY
responsibility for ANY damage that may be caused to your Amiga.
An attempt to change your own PALs shall be done SOLELY AT YOUR OWN
RISK!
Before doing any work on the inside of your Amiga, proper steps should be
taken to insure you are in a static free environment. Static electricity
can cause severe damage to chips. Static mats help a great deal, but
additional precautions should be taken.
The actual chips that will be replaced, are PALs J and K. These two chips
are found on your daughter board. To gain access, you must first remove the
screws from the bottom of your Amiga. This will allow you to remove the
plastic cover. Then remove the metal shield that you will find on the
inside of your machine. The daughter board is the smaller board that sits
about 1 inch above the mother board to the left of your disk drive. When
you take the metal shield off, you will be looking at the bottom side of
the daughter board. Remove the three screws that secure the daughter board,
then remove the board. BE CAREFUL! Most pressure in removing the board
should be applied to the upper and lower right hand corner (looking at the
board from the front). Once the daughter board has been removed, you are
ready to go to work.
Locate chips J and K on your daughter board. You will notice that they are
soldered directly to your board. This means they ARE NOT socketed. This
also means the changing of the PALs is not as simple as just popping out a
few chips and popping in a few new ones, specially if you really don't know
what you are doing. I have a good idea of what I was doing ... my board was
fixed by someone who has a better idea of what they are doing after I
screwed it up.
The two chips (J and K) must now be removed. Unless you have some VERY
expensive equipment that can remove these chips in one piece, you'll have
to snip away each of the pins then remove the main body of the old chip.
Here's the part where I started making my errors.
After snipping off the pins and removing the main body of the chip you must
remove the pins from inside the holes in the board along with the old
solder. I used de-solder braid to do this. For those of you who are not
familiar with de-solder braid, it's a piece of copper braid that is placed
on top of the old solder. You then use your soldering iron to heat the
braid which in turn heats the solder. The melted solder is then absorbed by
the braid being removed from the hole when the braid is removed. The
process worked great for the solder removal, but it also worked great for
tracer removal. The idea is to leave the tracers in place, they are there
for a reason! (Tracers are those little lines you see running all over the
daughter board. They are actually thin lines of copper that connect the
chips to where they are supposed to be connected). This may sound like a
bigger problem than it really is. Before God created tracers, we had wires.
So wires are what you now see running all over my daughter board. The board
works just the same, it only looks a bit different. I suppose better
control over my soldering iron heat would have avoided this problem. A
better way to remove the old solder is with the use of a "solder sucker".
You can buy one at most electronics stores for less than $10.00. Place your
daughter board in a holder then heat the UNDERSIDE of the hole to be
cleared, placing the solder sucker on the TOP side. As soon as your solder
is melted, let the sucker rip! That should do a pretty good job of clearing
the old hole. This will have to be repeated for each of the 20 pins on each
chip. C Ltd. has explained to me that they have found this process to work
very well.
After all the solder has been removed, place the 20 pin sockets into the
board and solder them in. Once the sockets are in place insert the new PAL
chips, replace the daughter board and give Amy a try. When inserting the
PALs, a chip insertion tool is HIGHLY recommended. The pins on computer
chips are rather fragile. Improper alignment with the socket can bend a pin
and may possibly break it. The reason for the alignment problem is because
the pins are originally bent slightly outward, so it's wider than the
socket. A chip insertion tool will bend the pins inward in a uniform
fashion allowing for much easier alignment. If you can't afford the $8.00
for an insertion tool, the edge of your work table will do the trick.
Gently place the pins of one side of the chip against the edge of your
table. Apply pressure (not much!) to the opposite side causing the pins to
be bent slightly inward. Repeat the process for the other side then align
the chip with the socket and apply even pressure, sliding the chip into
it's socket. This technique works, but caution is needed.
If you did everything right, you will now be capable of operating a minimum
of four devices on the expansion bus; however, keep in mind that four
devices will most likely draw more power from your computer than is
specified by Commodore-Amiga. This can cause system failure. An additional
power supply will most likely be needed if you plan to add that many
devices.
There is a somewhat easier way to complete the PAL upgrade than what I have
just explained. This next method is slightly more expensive; however, it is
also MUCH safer. This method is easy. Write a check out to C Ltd. for
$50.00 and pack it safely with your Amiga. Send it off to C Ltd. and they
will do the fix for you. The $50.00 covers the labor and the chips.
Personally, I have to believe that the extra $26.50 is well worth it.
FIX #2:
The second fix for Amy that I mentioned earlier should be available now.
This fix is a hardware device that will attach to your
expansion bus PRIOR to the addition of other devices. This will allow up to
five additional expansion devices to properly operate, bypassing the need
for open heart surgery on Amy. C Ltd. and MicroBotics are both involved in
a joint venture to design and manufacture this device. The price has not
yet been announced.
Incidently, the PAL upgrade did cure all my 68020/881 problems. CSA's board
runs fine in my machine now. This is not to suggest that anyone thinking
about purchasing a CSA Turbo board will have problems, I know several
people who are running an 020/881 with no problems. You must simply keep in
mind that computers, much like people, have their own personalities.
I should note that not everyone agrees that the PAL chips are REALLY the
problem. In all cases, to function properly an expansion device should
conform to the hardware standards set forth from Commodore Amiga. Products
that take money saving short-cuts or improperly designed hardware can
cause many or all of the problems we've discussed when connected to the
expansion port of your Amiga. If at all possible, try out the device
before you buy. Short of that, ask your friends. The Amiga is a very
complex piece of equipment, and so are many devices that users are now
adding to their machines. I hope this article has shed some light on any
problems you may have experienced or might come across in the future.
I would like to thank Ed Lippert of C Ltd. for his technical support in the
preparation of this report. C Ltd. can be contacted at:
723 E. Skinner
Whichita, KS 67211
(316) 267-3807
END OF EXPANBLUES