Service And Troubleshooting - Kold-Draft GT301A Service Manual

Service and Troubleshooting

GB900/GB1000/GB1200/GB4
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These ice makers differ from other Kold-Draft ice makers in that two ice making
sections are refrigerated by one condensing unit. GB900/GB1000/GB1200 series are
electronic versions of the GB4.
The upper ice making section, also known as the "master," contains the controls
necessary to operate both sections simultaneously, while the lower or "slave" section
contains only those switches required to operate the actuator motor and water pump,
and to provide synchronization between the two water plates.
The GB4 uses an electrical synchronization system to ensure that both water plates are
fully closed before the freeze cycle begins, and to prevent repeated false harvesting
caused by "out of time" actuator motors.
There are two key parts in the synchronization system. A modified rotor in the top
actuator motor to slow the motor by 5 seconds, and a resistor between the upper and
lower actuator toggle switches to stall the lower motor in the closed position at the end
of harvest.
Synchronization is achieved by the lower actuator motor running slightly faster than the
upper motor, stalling upon direction reversal in the full upright (12 O'clock) position,
thus allowing the upper motor to catch up and synchronize. Upon upper motor direction
reversal, both motors continue to the end of the travel limit in the other direction and
repeat the same synchronization procedure. With ice in the evaporators, both plates go
down and stop together in the full down position automatically synchronized. When dry
cycling the cuber without ice, the lower actuator motor trips the lower actuator toggle
switch and raises ahead of the upper actuator motor. Synchronization occurs when the
lower actuator motor stalls after raising to the 12 O'clock position and waits for the
upper actuator motor to catch up.
This diagram shows the synchronization
circuit. The dotted lines indicate an
interim sub-circuit which was used from
9-81 until 1-83. To update any GB4, cut
the yellow/white in the upper channel,
tape the ends and install a modified rotor
kit (GBR-03110-01) in the upper actuator
motor. Cubers made before 9-81 do not
have the yellow/white wire in the upper
channel (unless they have been field
modified) and only the modified rotor is
required for updating.
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Kold-Draft Service & Parts Manual
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