Star Tech Journal

STAR*TEcH
January 1996
Journal
II
II
':Just the Facts, eh?"
John Liikala • Canadian Amusements • Burnaby, BC • Canada
TROUBLESHOOTING WILLIAMS
STAR TREK: THE NEXT GENERATION
BLOWN FUSE
SYMPTOM
CAUSE
F103 blows immediately when
the pinball is powered up. (Re-
fer to figure 2-9 for fuse location.)
TROUBLESHOOTING
Refer to your WPC schematic
manual and turn to the diagram
of the power driver board. (Note:
this is schematic package 16-
9057).
At this point we know that the
questionable circuit is the con-
tinuous duty. The next step is to
do a visual of the bottom of the
play-field to look for a burnt coil.
The single drop target down coil
was found to be at fault. This part
(SM26-600DC coil) was changed
along with the transistor that con-
trols the coil. (For 8-driver PCB
assembly location, refer to figure
2-2 and figure 2-14 for transistor
component location).
After these parts were changed
and the pinball was powered
. . . . . . . .
.
. . . .
. . . . . . . . .
back up for testing, everything
worked fine until smoke started
rising out of the Borg ship like it
took a direct hit (Please note: This
stinks as well!). The pinball was
shut off immediately and it was
noted that the replacement parts
had also failed.
" ... everything
In this case, as the CPU kept try-
ing to fire the coil, it heated up
and the transistor shorted out.
(Please note: I was only joking
about the direct hit on the Borg
Ship!)
worked fine until
smoke started
rising out of the
SoLurION
Borg ship like it
took a direct hit ...
The reason the coil kept burning
was because the CPU instructed
the driver board to fire the coil
simultaneously many times. Thi
coil can only handle an "on time"
of five seconds before the tran-
sistor breaks down and shorts
out.
H
Now, many questions can be
asked at this point, but I will keep
this short. The problem was origi-
nally the switch at the bottom of
the drop target. This switch was
not closing, therefore, the CPU
did not know that the drop tar-
get was down.
When fixing what may seem to
be a somewhat simple problem,
always try to investigate a little
further past the "Quick Fix"
stage.
Test all related functions of the
assembly in which you are repair ._
ing from the switch and on dow1.
to its related components.
. . . . . . . . . . .. . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . .