Play Meter

of the Game Doctors
An expensive assumption
We have been seeing quite a few
Bally electronic pins that have been
pulled from location and brought to
our shop with field serviceable prob-
lems. In most cases, the mechanic
has failed to carry his diagnosis far
enough to locate the actual source of
the problem .
Here's an example of a typical
problem and the chain of events that
caused this operator's game to be
down for a week . At this location, the
revenue lost was estimated to be
around $200 .
Thursday - the first out of order
call is received and the mechanic
goes to the location to find the 5-amp
fuse (F4) is blown . This fuse is in the
solenoid power circuit. If the fuse is
replaced , it blows again the moment
power is applied to the game .
Since the problem seems to be in
the solenoid circuit, the serviceman
pulls the solenoid driver board (A3)
and takes it back to the shop without
making any further tests to see what's
causing the fuse to blow .
Estimated cost of service call-
$20 .
Friday- The mechanic makes a
two-hour round trip journey to the
nearest distributor to get a replace-
ment solenoid driver board . The new
board is installed and the fuse is
replaced. This time the fuse remains
intact until the game starts to play the
power-up tune and then blows .
Replacing the fuse once more , it now
blows as soon as power is applied to
the game . The original problem is
back , the game is still out of order,
and the operator has invested an
additional $40 in gasoline and
man -hours as well as the exchange
board cost from the distributor .
Since the solenoid driver board
has been replaced , the mechanic
now (incorrectly) assumes the MPU
board to be bad, and pulls it for
exchange . ·I he game will be down
for the weekend because a new MPU
board cannot be obtained until
Monday .
Monday-Another trip to the
distributor for an exchange MPU
board . Replacing it does nothing to
help the game , and the machine is
finally pulled to our shop for a closer
look at the problem . Another $40 in
gasoline and man -hour costs is
spent, and the machine is still not
working .
Tuesday- The fault becomes ob-
vious when the solenoid driver
connectors are pulled off and the
fuse now remains intact. A quick
check with an ohmeter shows a short
for the 10-point chime driver transis-
tor (See July Play Meter for the
front-to -back method of checking
transistors with a V. 0 . M.) . Sure
enough! A visual inspection of the
chime assembly reveals a burned
coil. A burned coil and solenoid
driver transistor are both items that
can be replaced in the field (See
September Play Meter for solenoid
driver transistor replacement) .
Tuesday evening- The game is
back on location and making money .
The Joss of revenue has been ten
times what it should have been .
The point is that had this been an
electro-mechanical pin , every coil
would have been visually inspected
on location to find out which one had
blown the fuse . In this case , the
playfield was never even lifted to
look at the coils . When the replace-
ment solenoid driver board was
installed , the burned coil took the
driver transistor out again and the
symptoms of the original failure
returned .
Power supply and driver transistor
failures are going to be the most
common type of solid-state pinball
problems encountered by the field
mechanic . Fortunately , these two
problems are easy to understand and
diagnose . Don't be afraid to change a
voltage regulator or driver transistor
while on location . The Bally solid-
state pinball can provide an easy-to-
understand first step for the pin
mechanic who wants to climb the
ladder to solid-state repair proficien-
cy .
Interchangeable
logic boards
Did you know that the logic boards
for Gran Trac 10 and LeMans are
directly interchangable? That's right!
You can update your Gran Tracs bv
replacing the P .C.B . with a LeMans
board or avoid excessive downtime
by temporarily substituting a Gran
Trak P .C .B. if a faulty LeMans board
has to be pulled for repair .
Please note that Gran Trac 10 has
a three-.speed gearshift with reverse.
and LeMans has four foreward
"gears ." If the boards are interchang-
ed , the reverse gear position of the
GT 10 shifter becomes first gear, first
becomes second , second becomes
third , and third gear becomes fourth .
If a permanent board swap is made,
a new four-speed shift bezel (Atari
part 11005255-0 1) should be installed
to avoid player confusion.
Supertank
corrections
of the steps for the
Three
Supertank Modification One were
incorrectly listed in the November
issue of Play Meter (pages 84 and
85) . Here are those corrections :
Step 1- Ciip and lift L8 -13 .
Step 2 - Ciip and lift L8-1.
Step 8 - Add wire between 74107
Pin Three and 740 2 Pin Three.