Star Tech Journal

Issue: 1987-April - Vol 9 Issue 2

STAR*TECH Journal
Inside Switching Regulators (Part 2)
By Jarres Beck
Greater Southern Dist. Co.
Atlanta, Georgia
OK, there it is. The schematic shows the
main power handling circuit of our
switching regulator. I didn't include a
fuse on one of the AC inputs, so we will
just assume there is an external fuse in
place. The two AC terminals represent the
115V AC wall voltage input. Cl, C2, C3,
C4, and Ll compromise a noise filter. The
pur:rose is not so much to keep noise out,
as it is to keep it in.
BRl and CS form a very simple unregulated
DC supply. BRl full wave rectifies the
115V (rrns), and CS filters it to 163V DC.
TRl and TR2 are the switching transistors.
'Ihey alternately turn on and off to pulse
the 163V DC through Tl. Dl and D2 are used
to protect their associated transistors
from damage caused by collapsing field
spikes. Tl is used to take the high
voltage, high frequency pulses induced in
its primary, by the switching transistors,
and convert it to a low voltage, high
frequency AC source for our output.
'Ihat just about covers what the parts are
suppose to do, what about when they fail?
April 1987 (10]
Failure lt>des
If Cl or C4 shorts out (this is a very
co:rranon occurance) it would effectively
connect the two AC lines together.
Needless to say this would cause the fuse
to blow.
Hare comes the good one, if C2 or C3
shorts, and you don't have the case
grounded, you could end up with a supply
with a "hot" case. A nice surprise for you
when the +5 needs to be adjusted!
If BRl were to short it would cause the
fuse to go. On the other hand if it
opened, there would be no voltage for CS
to filter, and no output voltage.
If CS shorted, once again, the fuse would
blow. This assumes that the surge rating
of the bridge is higher than the fuse
protecting it. If not the BRl may also
fail.
Let's suppose CS became "leaky". The AC
ripple on the unregulated supply would
increase. This would reduce the effective
DC value of the supply, which in turn
would cause the regulator (not yet shown)
to increase the switching rate of the
transistors. The increase in the switching
rate would cause an increase in the
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MAIM P~W£R.. 1-/AAJDLIN.6 C.K.1
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STAR*TECH Journal
April 1987
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transistors current load. That causes heat
build up, and that causes premature
com:[X>nent failure.
The Player /SPECIAL FORCE
A short in TRl, TR2, Dl, or D2 would cause
excessive current flow through Tl, and
cause the fuse to blow.
Now here is a machine by Bally Midway
wherein the player can get into his/her
own private little war!
open diode would cause the transistor
it was protecting to eventually fail.
'!he playing field is set deep under the
glass which sets off a nice visual effect.
This two flipper game offers the player
the Free ball, Special, and, of course,
your Multi-ball play. What I like is the
many different ways you can work the ball
to the players advantage.
An
If one of the transistors opened up the
other would be pressed into taking up the
slack, and would also fail.
I think that should wrap it up for the
rnorrent. Next :rronth we'll cover the drive
to the transistors, and the output
section.
'
(11)
Before I go, I would like to thank all of
the people who helped me in my last minute
rush before the AGIB show, especially the
pleat STAR*TECH JOORNAL and PlayMeter.
Conversion Kits
Lowest prices in America!
For Sale:
Kit Price:
LEGEND OF KAGE - . . . . . . . . . . . . . . . . . . . . $395
LEGENDARY WINGS . . . . . . . . . . . . . . . . . . . $Call
RYGAR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $Call
EMPIRE CITY . . . . . . . . . . . . . . . . . . . . . . . . . . $Call
GLADIATOR .... . ... . ................ . $Call
ARKANOID . . . . . . . . . . . . . . . . . . . . . . . . . . . $645
CHOPLIFTER . . . . . . . . . . . . . . . . . . . . . . . . . . $595
MAT MANIA .............. .. .. ... ...... $475
GHOSTS 'N GOBLINS . . . . . . . . . . . . . . . . . . . $4 75
10 YARD FLIGHT ....................... $299
JAILBREAK .... . .... . .......... .. .. . .. . $375
TIGER HELi . . . . . . . . . . . . . . . . . . . . . . . . . . . . $495
1942 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $495
VIE AR KUNG FU . . . . . . . . . . . . . . . . . . . . . . . $325
SUPER BASKETBALL . . . . . . . . . . . . . . . . . . . . . $295
GALAGA Ill ........................... $345
RUSH 'N ATTACK .................. .. .. . $375
MANY MORE ....... . .... .. . ...... .. Cheap!
COIN DATA, IHO~
PO Box 1209, 107-E Dick
Buchanon St., Lavergne, TN 37086
615/793-9142
By
John 'Root' Pilarchik
Pennsauken, New Jersey
I found SPECIAL FORCE a little complicated
to figure out at first but, the more games
I played, the easier it became.
The player goes through a small battle
playing this game, collecting rockets,
bombs, capturing hostages, dropping bombs,
firing rockets at tanks, taking the
helicopter rarrp etc. Bonus ix>ints are
scattered throughout -with escape bonuses
and the go-for-wea:[X>n bonus; I could go on
and on ...
Both bottom side ramps have a small bumper
and a side door so that if the ball hits
the bumper a certain way, it will shoot
through the door and cone back into play.
This is a big plus!
SPECIAL FORCE is without a doubt going to
be a big winner in any location. This game
has class, is fun to play and the
challenge on the playing field is just
superb!
the by. . . The newer machines I've found
have a self adjusting score level, so that
if too many games are awarded, the replay
score will keep going up. This player
feels there should be a reasonable maximum
setting to give the players that are not
semi-pro's a fair chance at hitting on
score.
By
Play on ... Root

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