Subject: Early Williams Tech Tip
From: [email-masked] (richard.l.schieve)
Date: 15 May 92 19:31:50 GMT
Newsgroups: rec.games.video.arcade

Well, I've been collecting, fixing, and restoring mostly early 80's
video games for around 8 years now and have gotten pretty good at
working on them.  Some of these games have the same problems over
and over and I thought some of you might like to hear about some of
these problems.  Much of this is information I've sent directly to
people when they have posted requests for help.  I'm not an
electronics wizard or anything.  I've just spent enough time trying
to fix games that I've learned some typical failures.

Todays Tech Tip ;-) is on the early William's games, Defender,
Joust, Robotron, Stargate, Sinistar, Bubbles, and I think Blaster
but I've never worked on one.  These game all share the same basic
logic board arrangement as follows: 

-------------------    ------------          ------------  -------
|                 |    |          |          |          |  |     |
|                 |    |          |          |          |  | AUX |
|   CPU/VIDEO     |    | ROM/PIA  |          |  SOUND   |  | SND |
|                 |    |          |          |          |  |     |
|                 |    |          |          |          |  |     |
|                 |    ------------          ------------  -------
|                 |
|                 |    ----------
|                 |    |        |
|                 |    |        | <--INPUT
|                 |    ----------
|                 |
-------------------

The three boards on the left are often mounted on a metal plate.
The sound board is the same one used in pins and the AUX SND board
is only used in Sinistar (I'm not sure on Blaster).

The most common problem I've seen with these games are loose
connections that can become intermittent and sometimes overheat.  How
the loose connections affect on the game depends on where it is.
All these boards including the power supply boards not shown are
interconnected with female Molex connectors mating to male pins that
are mounted perpendicularly to the boards.  These male pins are
fairly heavy gauge and are a bit hard to solder to.  The solder
connection between the board and pin often cracks when taking the
connectors on and off.  Also, at the female end, the connection can
overheat if things get a bit corroded actually burning the connector
shell and the female pin looses it's spring tension.

People often complain of resets during game play.  There are some
software bugs (at least in Robotron) but more often than not the
resets are due to the +5 VDC supply dropping below what TTL devices
can operate with at the logic board itself.  The Molex connections
to and from the power supply board will often show signs of
overheating.  Try measuring the +5 at the power supply and again at
the logic boards.  If there is much of a difference and especially
if the logic board is seeing less than +4.7 or so you have
problems.  If the female end has overheated considerably the female
pin itself has lost spring tension and should be replaced.  Often
you can clean the male pins and work the female off and on a few
times to get by for a while but chances are the female pin should be
removed and replaced.  Many hack artist coin-op repair types will
simply cut off the female connector and solder wires right to the
male pins.  You see the same problems with Williams pinball games.

BTW, the software Robotron bug is supposed to go away if you turn
off the "Fancy Attract Mode" which does away with the explosion when
you zap a bad robot (thanks George).

Loose connections at the logic boards seem more often to be cracked
solder joints where the pins go through the boards.  Any time
unexpected things start happening while playing, it is worth the
time to pull the board and check out the solder joints.  I checked
out about 6 board sets the other day and half didn't work but were
fine after I resoldered the pins to the boards.

Also, make sure to clean excess flux after resoldering the pins.
I've seen too much left over flux scramble the inputs from the
control panel.  To clean excess flux I use 1,1,1-Trichloroethane
called Carbo-Chor at Ace.  It's amazing stuff as as strongly as it
smells and as well as it works it does not burn so it relatively
safe to use.  I use one of the cheapie stiff bristled "glue" brushes
and dip it in some trichlor and scrub away.

To people that have worked on these (and older Williams pinballs)
this is all old news.  I think that many that read this group have
not had their hands in a machine until they are forced to and often
have software backgrounds and are a bit afraid of the hardware.

If this is well received I'll put together some more.  If not, sorry
to have wasted the bandwidth.

				Rick Schieve
				[email-masked]