Betson Big Choice Test Jig
James Rice
Pocket Change America
Newark, Delaware
SUBJECT
In the Pocket Change America shop, we were
faced with a common technician's problem. Toe
lack of a piece of test equipment we required.
This particular problem involved something we
could test Big Choice Crane Rotary Control
boards on at any time.
Current direction diodes across each pair of
bulbs are used to direct current when the po-
larity shifts to reverse the motor. A transformer
with a 120 VAC primary and a 25.2 CT sec-
ondary was used for this project. The center tap
was unused and the primary was plugged into
an isolation transformer.
FOR STARTERS
Given the task of building a piece of applicable
test equipment. I began to grapple with the
necessity of making it compact. This seemed
difficult with the 72 volt DC load involved, but
with a suggestion from my supervisor, the
problem was simplified: We could use the same
voltage on both ends of the control board relays
involved, making the load voltage far more
manageable, and still verify the proper operation
of the board.
OPERATION
After everything is put together, the test jig is
used as follows:
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CONSTRUCTION
• I used number 1819 bulbs to simulate all the
control board outputs.
• A SPST pushbutton switch is sufficient for the
coin switch input.
• To simulate the Carriage Assembly operation
we require four switches: The home switch, left
limit switch, claw position switch, and the lever
switch.
• These switches have two NC and two NO
terminals and though you could use DPDT
switches, I found the old Nintendo control panel
switches had the same terminals.
• I used these switches for the joystick buttons
as well.
CABINET
I used a standard aluminum test chassis with
holes drilled to accommodate the switches and
bulbs. For each motor (forward, side and up-
down), I have two bulbs so we can simulate both
of the motor's directions.
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