
This Week With My Coleco ADAM  9802.16

by Richard F. Drushel  (drushel@apk.net)


I.  Return from Hiatus.

     Thank you for your patience...it's been since 17 November
1997 that I have produced a TWWMCA.  My end-of-semester teaching 
crunch hit about then, and didn't let up until Christmas; but I 
had let so many things slip at home that I used Christmas Break 
for them.  And of course, the start of the spring semester has 
its own crunch.  Now that all the plates are spinning again (like
the juggler at the circus), I have some space in my schedule
again for TWWMCA.


II.  Rescuing Some "Dead" ADAMs.

     A local computer junkie, Fred Horvat (some of you may
remember him from his brief stopover at ADAMcon IV), had some 
ADAM pieces and parts which he said were nonfunctional, taking up 
space, and needed to be moved somewhere...pack rat that I am, I 
told him I'd take what he had and see what I could do with it.  
Since he lives way on the west side of Cleveland, and I live on 
the east side, we decided to meet at a "neutral site" (a Block-
buster Video store he passes on his way home from work in Akron) 
for the pickup.

     When I met Fred, it turned out he hadn't been able to find
all the stuff he wanted to get rid of--only a couple of ADAM 
system units.  Perhaps as some compensation, he brought me a
working original IBM-PC system (the one with the cassette port, 
not the later XT) and color monitor.  Welcome to 1981 :-) but
I can put it to good use--each of my 4 daughters now has her own
computer.

     The ADAM system units were a bit dirty, and one was missing
the lid covering the 3 expansion slots.  Each had one tape drive 
and one of the all-plastic type of drive bay placeholders (as 
opposed to the earlier kind which had a metal frame).  There were 
no major scuffs or scratches, but one of the system units had a 
half-inch hole in it around the disk drive ADAMnet port.

     Standard operating procedure for me with new-found ADAMs
(reported to be working or not) is to completely disassemble them,
clean them up, then test them under power.  A few minutes with a 
Phillips-head screwdriver took care of the disassembly part.  The 
plastic case pieces were put into a laundry tub full of hot water 
and Tide detergent.  The metal shielding was intact on one system 
unit, missing except for the bottom memory board shield on the 
other.They weren't very corroded (sometimes they get quite rusty),
but had lots of dust, so I threw them into the detergent as well.

     For those of you who've never been inside an ADAM, there are
two circuit boards:  a rectangular "memory board" on the bottom, 
and a square "video board" on top.  The memory board has the 64K 
of RAM, the EOS and SmartWriter ROMs. the 3 internal expansion 
slots, the sideport expansion connector, the tape drive connect-
ors, and the ADAMnet master 6801 microcontroller.  The video
board has the video circuitry, the Z80 microprocessor, the
ColecoVision OS-7 ROM, the game controller connectors, and the 
game cartridge slot.  The video board is actually just a modif-
ied version of the ColecoVision video game board; the Expansion 
Module 3 version of the ADAM (which connects to a ColecoVision) 
has just the memory board.  In the ADAM, there is a ribbon cable
with edgecard connector between the memory and video boards.

     The circuit boards of both system units were revision D1-D3;
PROMs (no version labels) instead of EPROMS; 3-ROM configuration 
(8K EOS, 8K and 16K SmartWriter) instead of 4-ROM (8K EOS, 3 x 8K 
SmartWriter); master and tape 6801s socketed; memory I/O control-
ler soldered; lots of rework on the memory board (extra jumpers, 
capacitors, cut traces).  Based upon this, I expected to find R80 
SmartWriter when (if) the machines were booted. 

     There was one surprise inside the system unit which had the
hole in the case--a complete mouse nest made of pink fiberglass 
insulation!  This and other goodies were stuffed into the space 
between the outside of the case and the back wall of the internal 
expansion bay.  The case plastic is about a quarter inch thick; 
I can't imagine some rodent chewing away at that for very long...
but I don't know how else to interpret it.  My daughters were
pretty grossed out when I showed them the nest.

     The cases cleaned up nicely in the detergent.  Sometimes you
will find old stickum from labels which have fallen off, or from 
tape, which the detergent won't remove.  For this, I use lighter 
fluid (naphtha) and paper towels.  If the case is badly discolored 
(too long under fluorescent lights, or else owned by a smoker), 
there's not much you can do.  I have read reports that Formula 
409 stain remover plus one of those green Scotchbrite pot scrub-
bers can remove this kind of heavy staining (at the expense of 
the finish), but I've never tried it myself.

     Finally, I was able to put the circuit boards back in (minus
all the shielding) for the first powered tests.  The first system 
booted right away, with good video.  The second system had a 
scrambled screen, and the printer didn't give the normal carriage 
return/line feed expected when booting into the Electronic Type-
writer.  So, which board was bad--the memoryboard or the video 
board?  I decided to do a swap test using the first system unit; 
clearly 1 system worked!  So, it must be a bad memory board.  
However, the reciprocal test of memory board 2 plus video board 
1 also worked!  This suggested a dirty edgecard connector on the 
ribbon cable between the memory and video boards.  Cleaning the 
traces with a pencil eraser and reseating the connector a few
time cured the problem.

     You might be thinking that it's dangerous to troubleshoot 
by swapping--isn't it possible that a bad board will damage a 
good board, leaving you with a stack of blown boards?  Yes, it 
is possible.  My experience has been, however, that as long as 
the boards don't have dead short circuits in them (i.e., a 
direct connection between supply voltage and ground), there is
not much real danger.  Shorted boards can be identified by the
presence of burned traces, burned wires, or literally blown/
fried chips.  Such a board must have any damaged components 
removed and replaced, and the source of the short identified 
and fixed, before applying power.  Component-level trouble-
shooting is best left to experts.

     Now that I was sure both systems worked electrically, I put
everything back together properly, including all the shielding. 
For the system which was missing most of the shielding, I went 
to my ADAM junkbox and got the necessary pieces.  I tested both 
systems again after the shielding was installed, but before the 
cover was screwed down, just to make sure I didn't have any 
loose connections--it's really annoying to keep unscrewing the 
case more than a few times in one sitting :-)

     The last items to test were the tape drives.  Plug them in,
put in a tape (my Donkey Kong Super Game was the closest at hand),
pull the reset switch, and pray...luckily, both drives booted 
successfully.

     So, for the cost of a scoop of detergent and an afternoon's
time, I was able to add two more ADAM system units to my collect-
ion.  I have found many times, with many different kinds of 
machinery, that simple disassembly, cleaning, and reassembly 
resurrects many "dead" items.  Remember this the next time your 
ADAM flakes out.


III.  Next Time:  ADAM Schematics.

     I have some ADAM schematic diagrams in .GIF format.  They
aren't scans of Coleco schematics; I redid them using Canvas 3.5 
graphics software, so they are neat and legible :-).  I will put 
these up for anonymous ftp and talk about them next time.


     See you again next week!

     *Rich*

*****************************************************************

Note:  TWWMCA is archived.  Back issues are available via
anonymous ftp.

        ftp://junior.apk.net/pub/users/drushel/twwmca/

Files have the form wkyymmdd.txt, where yy=year, mm=month,
dd=day.

*****************************************************************
-- 
Richard F. Drushel, Ph.D.            | "Aplysia californica" is
your taxonomic
Department of Biology, Slug Division | nomenclature.  /  A slug,
by any other
Case Western Reserve University      | name, is still a slug by
nature.
Cleveland, Ohio  44106-7080  U.S.A.  |     -- apologies to Data,
"Ode to Spot"


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