."v
T DPADDL..
Atari's
Breakout
-A Problem
Solved
by Robin Minnear
of Game Doctors
As kind of a follow-up to May's
"Technical Topics," this month I
will describe a modification that w ill
help to eliminate a very common
problem that occurs on Atari's
Breakout.
Breakout is available in an upright
and a cocktail table version . The
upright model has one pot that is
shared by both players . The cocktail
version has one pot for each player.
The picture also flips to face each
player when it's his turn .
Because the cocktail version has
two pots, when two people play, the
logic board must listen first to one
pot and then to the other pot. This
switching is achieved by the circuit in
Figure 1. This is also where the
problem occurs.
In Figure 1 you can see that there
are provisions for two pots. Pot # 1 is
the pot that is used in the upright
version. Pot # 2 is the pot that is used
for the second player in the cocktail
version .
Unlike the input circuit discussed
in May, the pots put out a voltage
between zero and five volts, de-
pending on where the pot is set. This
variable information is commonly
called analog information .
Because this information is ana-
log , digital devices can 't deal with it.
So a special device called an analog
switch is used .
Figure 2 is the diagram for the 4016
quad CMOS analog switch that is
used in Figure 1. The 4016 has four
separate analog switches in one
package . Each analog switch has
one input, one output and one
control or enable pin .
According to the truth table in
Figure 1: whatever analog voltage
level that is present on the input,
appears on the output when the
44
CIRCUIT
POT
ON .
POT
TWO
Pl,.AV. R 2
CONDIT IONAL
fil ia l
4016
OUAD
r-----....,
ANALDO
. W IT CH
I ~'
'.~
o~.
C ONTRO L
':9-'
1 1 ~ ,0
12~
71
OND
X: A NALOO VDLTAQ.
10
1
z : HI IMP . DANe .
vee
FlO
a
+ 5V
IN.14
~
100DHM
FlO 3
OND
control pin is " hi". When the control
pin is "Iow," the output changes to
the " Z" or high impedance state and
acts like it doesn't exist.
Looking again at Figure 1, we find
that two of the four analog switches
are used to choose which pot's
information will be let through to the
paddle circuit . This is achieved by
the addition of a 7404 invertor (E9)
placed between the control pins of
the two analog switches. Because of
this invertor, if 09 pin 6 is "10"
(disabling the # 2 analog switch) , 09
pin 12 is "hi" (enabling the #1 analog
switch), (lnd vice-versa . A signal
labeled " Player 2 conditional, "
which is generated elsewhere, de-
termines which analog switch is
enabled . The outputs of both analog
switches are tied together and go
onto the paddle generation circuit.
The problem that commonly
occurs is that the 4016 09) keeps
blowing which causes the loss of
paddle movement. The reason that
this 4016 goes so often is that
" Old Man Static ." To make things
worse, the 4016 is a member of the
CMOS (complimentary metal-oxide
semi conductor) family. CMOS
devices are more susceptible to
static than normal TTL devices.
There are two ways to eliminate
this situation . The first, and best,
way is to try to eliminate the static
from reaching the 4016 . This can be
done by adding a few components to
the inputs of the analog switches.
Figure 3 is a schematic of a static
filter network . By adding this
network to the inputs of both analog
switches (pins 8 and 11), most of the
static is filtered out before it reaches
the 4016's. Each network consists of
two signal diodes (1 N914 or equiv.),
one .01 microfarad capacitor and
one 100 OHM resistor .
The best way to perform this
modification is to first install an IC
socket in place of the 4016. This will
enable you to quickly replace the
chip in the field should it go again .
Then you can add the static filter
network . If your Breakout is in the
upright cabinet, you can get off a
little cheaper than the cocktail
version . First of all, you only have to
modify the Player # 1 analog switch.
The Player # 1 analog switch input is
at location 0 -9 pin 11.
I have on occasion gone out to a
location on a Friday night and
performed an emergency fix on a
Breakout that had a bad 4016 . Please
keep in mind that I did this on the
upright version only .
The first thing I did was to clip and
lift pins 8, 9, 10 and 11 on device 0 -9.
Then I put a jumper wire from the
pad of 0 -9 pin 11 to the pad of 0 -9
pin 10. In short, I disabled the analog
switches and by-passed the player #1
analog switch with a jumper. But
until the 4016 is replaced , this logic
board will not work in the cocktail
version .
I generally do not recommend that
people by-pass input buffers,opto-
isolators, etc . but I do believe that
down time kills. If you are unsure
about how to perform any mod-
ifications, feel free to give me a call at
Game Doctors (408 / 294-7752) or
write to me at Play Meter.