SCRAM ASSEMBLY
                         ==============


WHAT IS INVOLVED

If you are interested in the SCRAM 2000 and would like to get one going,
you need to know just what is involved.

If you are going to build it yourself, you have to know how to solder!
Count up the component pins on the main PCB - you will find there
are more than 500! You will need a fine tipped soldering iron and fine
multi-core solder. No big deal really, but don't attack the PCB with
some great hulking 100 Watt Plumber's Friend. The RAM array is quite
dense and care must be taken not to make solder bridges, but everything
else is fairly routine.

If you don't know how to solder, get someone good to give you some
pointers and then practice a bit on some Radio Shack breadboard until
you have the hang of it. You can buy a lot of resistors and breadboard
for $5 and that will give you many hours of practice. When you feel
confident, then proceed at will.

An experienced technician could probably build a SCRAM 2000 in 2 - 3
hours. If something goes wrong, a SCRAM board is not that hard to fix -
it is fairly modular in design - the fault can usually be located
visually. If you have access to a working SCRAM, chip swapping will
resolve the problem in no time. With a full working set of schematics
(provided on this disk) and PCB layout (also provided) the SCRAM 2000 is
not a mystery. The SCRAM 2000 is easy to get going (excluding assembly
errors). The production version of the SCRAM 2000 currently enjoys a
very low return rate - simple, reliable technology.

If the preceding paragraphs leave you perplexed and worried, take heart.
One reason for releasing the SCRAM 2000 design onto Public Domain was to
encourage broad support for an Open Architecture SCSI/RAM peripheral in
the Amiga community. Even if you have ten thumbs and two left feet,
chances are that you know someone who is technical or you have access to
a User Group or Computer Club that has a technical member. The SCRAM 2000
can be a cheap way to upgrade your Amiga 500 - especially if you can
provide some of your own parts and labour.



MAIN PCB ASSEMBLY

Start by installing all the sockets - GAL sockets, EPROM socket, PLCC
socket.  If you like, install sockets for all the glue chips - LS257,
LS373, LS32, HCT393, F86, F521. The only CMOS device is the HCT393 which
should be handled with care - so socketing this device (U26) may make
life easier. TTL is pretty hard to blow up, so soldering it directly to
the board is fairly safe.

Next, solder in the RAM sockets. This is a tricky bit, and if you
succeed here you should be OK with the rest of the assembly. If you run
into problems, at least you won't have done any major damage and there
is time to get some help. Only use a low powered soldering iron, and be
carefull! Don't do any dry joints and watch for solder bridges. Fix each
socket (or strip) in place by soldering a pin at either end. When all
the sockets are in place, go down each column soldering every pin.
Double check for unsoldered pins - in my experience this is the most
common cause of handsoldered boards not working.

Now solder in the TTL components - assuming you didn't socket them. Try
not to solder any chips in upside down or back to front ( don't laugh
I've seen it.)

Solder in Resistors, R-SIPs, Electros, Bypass caps, and Jumper blocks.
This is the time to clean the PCB with FLUX CLEANER if you want to. This
is important if using Acid core solder - ask someone who knows about
this if unsure.

NOTE - If using flux cleaner, make sure you don't let any get into the
sockets on the component side of the card - this can lead to unreliable
connections and extreme depression.

Finally, you solder in place all the chunky bits. The DB25, toggle
switch and 50 way headers - if you like you could tack the DB25 to the
PCB with Super Glue, but it is probably unnecessary.

Now you can mount the back panel and LEDs. Observe correct polarity for
the LEDs - the long lead is positive and this is marked on the silk
screen overlay. The SCRAM PCB should now be complete. Double check
everything and visually inspect the board for:-

Solder in a short (2") power cable for the Hard Drive. Triple check the
+5 and +12 wires. Don't leave this to chance. You should be able to get
a suitable connector - just open up your PC Clone and snip a spare one off.

  o Unsoldered pins
  o Solder bridges (tiny slivers of solder between adjacent pins)
  o Dry joints (dull, misshapen, blobby solder joints)


           
PRELIMINARY TESTING

Before applying power, do some preliminary testing of the board. A
multimeter is all you need. Do the following tests (preferably with the
extender card plugged in).

  o use the continuity tester to check all GND pins and +5 pins
  o measure resistance between GND and +5 - should be about 20-40 ohms
  o check a few point to point connections for 0 ohms

Don't plug in RAMs,EPROM, Custom Chips or SCSI chip until the board has
been powered up with the smoke test. If you pass this test, install the
custom chips, set the RAM jumpers to 0M (both shorted) and if you get the
AutoConfig LED (green) on and a working Amiga, then you are looking
good - now you can test RAM.

Be careful plugging ZIP RAMs in the sockets. Check that all pins are
seated and none are splayed outside the socket. Double check that pin 1
is to the top of the board. Populate from Bank 0 -> 3. Make sure the 4M
jumper is set correctly.

There, easy!



NJJ