Star Tech Journal
Issue: 1992-April - Vol 14 Issue 2 - Page 8
STAR*TECH Joumal
April 1992
Gottlieb System 80
Driver Board Revisited
Mario Van Cleave
Classic Pinball
Salinas, California
SUBJECT
A recent article pointed out a
troublesome problem with the
design of the Gottlieb System 80
Driver Board.
PROBLEM
Loss of ground on the driver tran-
sistors results in self-energizing
solenoids and damage to the
driver transistors, latch I.C.'s
and even the coils themselves.
Jumpering the logic and transis-
tor grounds together on the
driver board is a very good insur-
ance policy, but the job is far from
finished.
MONTE CARLO
As an example, let's look at Monte
Carlo, the Dome, Ramp, and
Spin-A-Ball circuit.
To drive these paralleled #67
lamps other transistors had to be
added, introducing the MJ 2955
(PNP sister to the 2N3055).
These four transistors were
mounted in a common-collector
arrangement on a metal bracket
under the playfield near the ball
shooter. They were slaved to Q15
thru Q18 on the driver board.
SYMPI'OM
The smoking gun here is a prob-
lem that Premier was aware of
with the game Gold Wings. If
these bright lights locked on, the
plastic domes and lenses would
melt.
To add insult to injury here: not
only is the game at this point
playable, but the player is treated
to a temporary smoke and fire-
works show at your expense!
Also, the metal bracket the tran-
sistors are mounted on, gets hot
enough to scorch the bottom of
the playfield and discolor the art-
work above.
DESIGN
The problem here is that the
ground for these transistors is
not in any way tied to the driver
board. A separate wire (white)
labeled "9" is used to ground the
transistor cases to the trans-
former body in the bottom of the
cabinet.
~
The mating connectors here loose
contact over a period of time. If
the connector looses contact, the
power transistors are left floating
which stresses the smaller MPS-
U45 beyond it's means -due to
the lack of any current limiting
between the two transistors.
This will cause failure of all four
power transistors, all four driver
transistors, and possibly the
latch.
SOLUTION
41\
YW
WW
"''
4A
-PW
WW
,:::t
The solution is to daisy chain the
separate ground wires in any con-
venient place. Then attach to any
of the chained wires a firm
ground to the transformer body
with a threaded screw.
This will not defeat any of the
connectors and allow them to
"share the load."
~
April 1992
Gottlieb System 80
Driver Board Revisited
Mario Van Cleave
Classic Pinball
Salinas, California
SUBJECT
A recent article pointed out a
troublesome problem with the
design of the Gottlieb System 80
Driver Board.
PROBLEM
Loss of ground on the driver tran-
sistors results in self-energizing
solenoids and damage to the
driver transistors, latch I.C.'s
and even the coils themselves.
Jumpering the logic and transis-
tor grounds together on the
driver board is a very good insur-
ance policy, but the job is far from
finished.
MONTE CARLO
As an example, let's look at Monte
Carlo, the Dome, Ramp, and
Spin-A-Ball circuit.
To drive these paralleled #67
lamps other transistors had to be
added, introducing the MJ 2955
(PNP sister to the 2N3055).
These four transistors were
mounted in a common-collector
arrangement on a metal bracket
under the playfield near the ball
shooter. They were slaved to Q15
thru Q18 on the driver board.
SYMPI'OM
The smoking gun here is a prob-
lem that Premier was aware of
with the game Gold Wings. If
these bright lights locked on, the
plastic domes and lenses would
melt.
To add insult to injury here: not
only is the game at this point
playable, but the player is treated
to a temporary smoke and fire-
works show at your expense!
Also, the metal bracket the tran-
sistors are mounted on, gets hot
enough to scorch the bottom of
the playfield and discolor the art-
work above.
DESIGN
The problem here is that the
ground for these transistors is
not in any way tied to the driver
board. A separate wire (white)
labeled "9" is used to ground the
transistor cases to the trans-
former body in the bottom of the
cabinet.
~
The mating connectors here loose
contact over a period of time. If
the connector looses contact, the
power transistors are left floating
which stresses the smaller MPS-
U45 beyond it's means -due to
the lack of any current limiting
between the two transistors.
This will cause failure of all four
power transistors, all four driver
transistors, and possibly the
latch.
SOLUTION
41\
YW
WW
"''
4A
-PW
WW
,:::t
The solution is to daisy chain the
separate ground wires in any con-
venient place. Then attach to any
of the chained wires a firm
ground to the transformer body
with a threaded screw.
This will not defeat any of the
connectors and allow them to
"share the load."
~
Future scanning projects are planned by the International Arcade Museum Library (IAML).