TECHNICAL TOPICS
By Randy Fromm
Solid State Pinball
The decision to purchase a
solid-state pinball over an electro-
mechanical game is an important
first step for an operator. Certainly
one of the most critical evaluations
before buying one must be in the
area of service. Since downtime
directly affects income, the opera-
tor's mechanic becomes a key man
for consultation before the deal is
made .
"Can you fix it when it fails? " is a
query whose answer should have a
significant effect on the final
decision .
During the coming
months, we will take a brief look at
solid-state pins and an entirely
different way to skin a cat!
Bally's Solid-State Pinball
Who says solid-state pins have to
be bizarre and futuristic? Bally's
electronic pinball design has a
familiar game package that is easily
accepted by die-hard pinball players
and novitiates alike .
If these
computerized chameleons of Chica-
go's coin cartel didn't have seven
segment electronic readouts , the
average player would be hard
pressed to tell them from the
electro-mechanical games of the
past.
Once inside, however, things are
very different. The relays, stepping
units, and score motors have been
replaced by microprocessing units
(MPU) , lamp, and solenoid driver
modules. To the mechanic who has
always thought of the pinball
machine as his last electro-mechani-
cal refuge , this new pin design
might be a little scary. Fortunately,
the folks at Bally have put a lot of
thought into designing a game that
can be easily serviced by a field
mechanic with a V.O .M .
The service book is full of test
procedures and trouble-shooting
guides that can really help to
pinpoint the trouble.
Typical of
microprocessor controlled games,
Bally's electronic pin will run a
self-test to check for bad lamps or
lamp drivers, bad score display
segments, bad solenoids or solenoid
drivers and stuck switch contacts .
These quick checks can really help
out with routine service.
For those who are, perhaps, a bit
more knowledgeable (or daring !) the
Bally electronic pin will run an
internal sequence to examine vari-
ous circuits in the microprocessing
unit. This makes it possible to repair
a bad M PU board in the field or to
isolate the MPU board as being
faulty by exchange .
It is most
important to realize that outs.ide
world influences can produce mis-
leading results when testing the
MPU .
Before pulling the MPU
board , perform the tests that are
outlined in the manual. If you have
two Bally electronic pins in the same
location, the boards can be swap-
ped around to double-check your
diagnoses .
Switch Matrix
At first glance, the playfield and
front door contacts of the electronic
pins look much the same as the
electro-mechanical counterparts. A
closer examination, however, re-
veals that a diode has been placed in
series with each pair of contacts on
the game . Once again , things are
not what they seem to be in this
new system, for instead of having a
common wire to each switch as in
previously engineered pin games
(see figure 1) the playfield and front
door switches are part of a matrix
system that feeds directly into an
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