Play Meter

Issue: 1976 April - Vol 2 Num 4

The diode is one of the simplest
devices of the solid-state world and
one of the most important.
It
changes AC (alternating current)
into DC (direct current) ; it allows
signals to go in one direction only; it
clamps voltages ; it suppresses.
noise; etc . The list is long, which
only attests to its usefulness.
Because of its many uses, ser-
vicemen often become confused
about how this device works, which
often leads to replacement of parts
that do not need replacing . Not
only valuable time and parts are
wasted , but the diode becomes
more of a mystery. The serviceman
is a little less sure about diodes and
their various uses.
One of the best teachers I ever
knew had a saying , '" Learn the
basics ." Once you know the basic
operation of a diode , its uses
become obvious and circuit analysis
becomes easier and less time is
needed to find faults . A diode is
simply a device which allows elec-
tricity to flow in one direction
only--an important point .
Because current flows in one
direction , the majority of diodes can
be checked satisfactorily with an
ordinary ohmmeter. When prepar-
ing to check a diode, first determine
which end is the cathode . The
cathode is almost always marked
one way or another .
When using an ohmmeter to test
a diode, make certain you are
absolutely sure of the polarity of the
ohmmeter leads . It is a good idea to
measure the ohmmeter leads with a
voltmeter to determine polarity .
Then mark the polarity of the
ohmmeter leads directly on the
leads or the ohmmeter case with a
felt marking pen . Th is is especially
helpful when using more than one
ohmmeter, since ohmmeter leads
can be either polarity .
Connect the negative ohmmeter
lead to Ithe cathode and the positive
lead to the anode . Thb hookup
forward biases the diode and the
ohmmeter reading should be low for
a good diode.
Connecting the
positive ohmmeter lead to the
cathode and the negative lead to the
anode, reverse biases the diode,
giving a high resistance reading .
It's important to check the resis-
tance in the forward direction on the
46
By PERRY MILLER
Rx1 scale of the ohmmeter . Other
scales will sometimes give erron -
eous readings because the ohm -
meter is not forward biasing the
diode enough to cause full conduc-
tion . Inversely, when checking the
reverse direction , use a high
enough resistance scale to deter-
mine the reverse resistance . The
ratio between reverse and forward
resistance should be at least 10 to 1.
Most diodes will have more than 100
to 1 back-to-front ratio. A typical
silicone diode will measure about 20
ohms forward resistance and over
100,000 ohms back resistance .
Diodes can be measured while still
in the circuit, but because of parallel
circuit resistance , the diode will read
differently then when the diode is
out of the circuit . Even so, the
diode will show a forward -to-back
resistance greater than the reverse
resistance . If tghere is any doubt in
your mind about the reading, lift one
end of the diode from the circuit and
measure the diode again .
" POWER SUPPL Y DIODES ARE
BURNING UP .. . and the two diodes·
near the connector burned up. On
one board they burned a hole
through the board . I replaced the
diodes with the ones sent from the
factory , but they lasted only a
week . "
This is a common problem with
the earlier Paddle Ball models . The
power supply diodes are under-
rated.
Replace the diodes with
silicon rectifiers rated at 50 PIV / 3
amps (Radio Shack #276 - 1141) .
You will have to drill out the holes
with a 1-16" drill because the diode
leads are a large diameter. Because
the drill will drill out the " feed -thru "
hole, make sure you solder the
diode leads on both sides of the
printed circuit board.
ATARl's TANK-- Power Supply
Diodes are Burning up. This is the
same problem that occurred on the
earlier Williams' Paddle Ball 2-Player
Tennis. The power supply diodes
should be replaced with silicon
rectifiers rated at 50 PIV / 3 amps
(Radio Shack #276-1141) . You will
have to drill out the holes with a
1-16" drill because the diode leads
are a larger diameter . Because the
drill will drill out the plated thru -hole
make sure you solder the diode
leads on both sides of the printed
circuit board .
CLEANING PLEXIGLASS. Most
manufacturers recommend a mild
detergent and a soft cloth for
cleaning plexiglass.
One of the
best " mild detergents" for the job is
Shaklee' s Basic-H . Basic-H will not
only clean the plexiglass, but also
clear up those minor scratches . Use
a quart container and mix YJ
Basic-H with % water and you ' re all
set to clean those dirty plexiglass
face plates .
INCREASE
INCANDESCENT
LAMP LIFE. Are you constantly
faced with annoying service calls to
replace burned -out bulbs?
Then
replace the bulbs with a higher
voltage rated bulb, i.e., #47 replace
with #1488 .
The bulb will be
dimmer, but you will increase the
life of the bulb by a factor of 25 .
Another solution to this problem
is to place a diode in series with the
lamp . Disconnect the lead from the
lamp socket and solder a 30 PIV / 1
ampere diode to the socket. Solder
the disconnected wire to the free
end of the diode . If the lamp will not
light, reverse the diode . Use tap or
shrinkable tubing to dress up the
solder connection between the wire
and the diode .
SHRINKABLE TUBING. Shrink-
able tubing is an insulated sleeving
which shrinks when heat is applied
and has replaced electrical tape in
just about every application . It is
used when exposed wire connec-
tions need to be insulated , such as
insulating solder connections on a
connector.
Before soldering the
w ire slide a piece of shrinkable
tubing over the wire , solder the wire
to the connector and then slide the
shrinkable tubing over the solder
connection . You can shrink the
tubing by using a lighted match .
Just place the match flame below
the shrinkable tubing and watch it
shrink .
A shrinkable tubing comes in
many different sizes and colors and
can be purchased at most electronic
stores.
Make sure the heat-shrinkable
tubing will shrink to half its original
size . Radio Shack has a package of
heat-shrinkable tubing with assorted
colors and sizes (#278-1627). Get a
package for your tool box . You will
find many uses for this material.
Common
complaints
One of the most difficult games in
the industry for a service technician
to master is not the video game or
microprocessor game, according to
C.A . Robinson head technician
Mike f-ia11, but the pinball game .
For Hall, " it's not a matter of
what problem you encounter, but
how you go about solving it ."
Despite observing that philosophy
himself, California operator Gene
Beley's most common and aggrava-
ting service problem involves coin
returns. " There's a need for more
sophistication in coin rejectors,"
Beley laments . Beley, who operates
most of his games in bowling alley
locations, has lots of trouble with
flattened pennies " that don't seem
to be able to get through vending
machine rejectors , but play havoc
w ith games coin units ." Lee Phipps,
the manager of the bowling alley,
told Beley coin return complaints
are the most prominent among the
game room gripes he receives.
Norm Ca lfin , co-owner of a chain
of arcades in Michigan, agrees with
Beley's assessment of the need for
more sophisticated coin acceptor /
rejector equipment on today's ex-
pensive and sophisticated games .
But his chief technician , Gary
Burton , spends his time battling
frustrating pinball machine prob-
lems. One of his most serious
problems, says Burton, is having
balls get stuck behind the rubbers
on the bumpers because of the extra
hard kick provided by DC power.
DC kickers at the bottom of many
pin tables come outside of the
rubbers, Burton said .
Seitch decks coming from the
fa ctory also present a problem , he
went on , because they are either not
tightened enough or they shrink and
loosen . He also feels pin table legs
are not reinforced strongly enough
because they bend easily through
customer abuse or simple moving .
Leg bolts often loosen up and
become wobbly . The screw holes of
th e bolts usually become stripped
after a few t imes of tightening
Those common non -technical
service problems are more frustra -
tion than anything else, Burton
remarked , but hp. wished manufac-
(
PlAt'METER
(Con tinuedfrom page4J)
ufactured by Nintendo Company
Ltd. , of Kyoto , Japan , have been
released in the U. S. by Sega of
America, Nintendo' s exclusive U. S.
factory representative, according to
Sega's Malcolm E.A . Kaufman .
The games are called Wild Gun-
man and Shooting Trainer and both
are set at 50 cent play .
To play the Wild Gunman, the
player straps on a realistic six-
shooter and holster and attempts to
outdraw five gunmen who appear
on a 4-foot-by-4-foot motion picture
screen . Each gunman appears in a
different setting .
At the start signal, the shoot-out
begins . If the player outdraws the
gunman , then the desperado falls to
the ground in an exciting stunt
man fashion; if thp. reverse happens,
then the gunman twirls his six-
shooter and tells the player "you
lost. "
Throughout the playing time , the
sound track on the film provides a
chilling realism, Kaufman comment-
ed . The pistol shot is real and so is
the slapping of leather as the
gunman draws and shoots. They are
the kind of sound effects which
create a sense of involvement on the
part of the player, he added .
In Shooting Trainer, the player
shoots at bottles on the screen
using an authentic rifle . The bottle~
are placed in a picturesque western
setting .
The player begins by shooting at a
few bottles, which disappear . But
they are replaced by a new set of
bottles which appear on the screen.
As the game goes on, the bottles
disappear and re-appear at a quick-
ening pace, and then , suddenly,
they begin flying in the air and the
player has to shoot them on the fly
before they hit the ground .
As the player hits each bottle,
there is, in addition to the rifle shot
the sound of breaking glass; plu~
the visual explosion of the bottle on
the screen .
Kaufman said the games have
been modified to Sega specifica-
tions for U.S . operation . In addition,
Sega is stocking spare parts at its
California facility.
These games are now on the way
to Sega distributors .
r---------------,
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1 - 2 - 4 PLA Y ERS
FACT ORY WARRANT EE •
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UNITED STATES MARKETING, INC.


Scottsdale, Arizon a 85251


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Marketing Division
602·994·3800
Telex
910·950·1151
Parts Division
800·528·1343
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