1'.""I'AR TECH JOURNAL
March 1994
WILLIAMS PINBALL
WEAK FLIPPER Fix
Jonathan Deitch
Namco Cyberstation
Atlanta, Georgia
SUBJECT
Williams Fliptronic II weak flip-
per fix. Game: Indiana Jones.
PROBLEM
Left flipper flips very weakly.
While troubleshooting the flipper
problem, I received a CPU ROM
upgrade from L-5
to L-7. (With the
L-7 ROM in-
stalled, a new
problem devel-
oped; the upper
playfield stopped
tilting left during
normal
game
play, but worked
fine in test mode ...
go figure).
the flipper circuits except the flip-
per paddle itself, the Williams
tech suggested I check the flipper
opto switches and driver chips. I
swapped the left and right flipper
opto boards with no improve-
ment on the weak flipper. The
This is a potential
problem for any
Fliptronic II with
an inexplicable
weak flipper. E
pecially after re
placing every-
thing else and it's
still sluggish.
NOTE
.TROUBLESHOOT•
ING
After several attempts to isolate
the problem, I had replaced the
coil, the coil stop, the crank, the
sleeve, and the lower left flipper's
two TIP120 drive transistors and
a single TIP36C. No dice.
per buttons to control the upper
playfield. Replacing the LM339
comparator (U4) fixed both
problems. Nice strong flip and
smooth motion of the upper
playfield with the L-7 ROM.
only other link in the flipper
switch circuit is the LM339 com-
parator that is driven by these
optos.
SOLUTION
That the same
comparators are
also connected to
each flipper's
EOS switches U4 and U6 on the
Fliptronic II board are LM339s.
U4 is controlled by the lower left
and lower right opto and EOS
switches. U6 is controlled by the
upper left and upper right opto
and EOS switches.
The LM339 comparitor was inter-
I called Williams and confirmed mittent. While this didn't bother
that the differences in the L-5 and the flipper too much (it didn't re- It is possible for only one part of
an LM339 to go bad ... so you
tract much before it re-energized)
L-7 ROMs didn't cause weak flip-
pers, but L-7 did have a timing it caused a lack of crispness in the could have one malfunctioninf
opto or EOS circuit making a flip-
change to reduce heating in the flipper action itself, making it feel
upper playfield motor. As I had sluggish. It also drove the CPU per malfunction while the other
flippers work perfectly fine.
already replaced everything in batty when trying to read the flip-
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