Star Tech Journal

21
STAR*TECH JOURNAL/JULY 1983
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onvers1ons
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Featuring:
By Mark "Bear'' Attebery, Vending International Corp., San Juan Capistrano, CA
Hello out there! Listen folks, I don't want you to think that I'm" getting down" on you or anything,
but I'm not even hearing I/10th of the non-video unit solutions that I know are out there! Yes,
every month I try to go to various manufacturers and get info on retrofit kits, modifications, etc.,
but I want to give you the type of help that I wanted when I was fixing units at stores. The only way
I can do that is ifl hear what your questions are! So call me at 1-800-821-8990 and talk to me! OK,
enough griping.
Everyone gets in a good mood by thinking about the fact that in one more month, all of those
little rug rats will be back in school! Doesn't that make you smile? Good!
This month' s Future Tech Lesson #5 is going to be a little short, but more complicated than in
the past So pay close attention to the details! As you may have noticed, Sega Electronics' series
called "The ROM Line" has paralleled mine very closely in explaining AND, NAND, OR,
NOR, NOT Logic and SSI functions. This has happened entirely by chance and has not been done
on purpose! Since there are so many aspects of SSI that you need to learn, we are going to branch
off in a different direction for a month or two.
Power Supplles
One of the most common game failures to occur in our industry is that of power supplies. All power
supplies are basically the same: An AC signal is run through a rectifier to make it appear DC and
then run through capacitors to "filter out" ripple.
First, let' s look at the similarities of all power supplies. All power supplies have an AC source
::~~~y consisting of 38vac or l ~
, thus
e a s
transformEer
s
is usually found, and its schematic diagram
Secoodaly
1Prima,y
WAR
of the
WORLDS-
115vac
30vac
AC P1uo
Transformer
Plug-in conversion for
STAR CASTLE or
ARMOR ATTACK
BRIX
BURGERT/ME
BUMP 'N' JUMP
ZOAR
Now, the way that a transformer works is this: In a step-down transformer, there will be two
turns in the primary for every one turn in the secondary. This is a 2: 1 ratio. This ratio would mean
that 115vac would be dropped to 57.5vac. So . . .
.ill
2 - -
57 • 5 an dill
57.5
= 2
So in order to find the ratio of turns for 30vac, you would use
115
30 = 3.8333 turns.
Since it is difficult to make 3.8333 turns to 1, let's see what a 4:1 ratio comes to be at 115vac
primary.
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1
1 5 = 28.75vac
Close enough fo.r government work! The next thing you will want to do is change the 28. 7 5 vac into
a DC value. This is done using a diode as a rectifier. Now, diodes are used for different functions
and you may become confused when a diode is called a rectifier and vice versa. Diodes designed
for switching at high frequencies cannot handle this type of power application. Power = I x E
( current x voltage). Rectifier diodes cannot handle switching at high frequencies, but they both let
the current travel in one direction.
A single diode can be used for rectification, but the wave forms of the circuit will look like the
following:
r.z.~
07/)
A to B without the rest of the circuit would be an AC wave form:
Ov - - - ~ -
~
1985 Friendship Dr.
Suite J
El Cajon, CA 92020
C to D without the rest of the circuit would be an unfiltered DC wave form:
Continued on next page.