MULTISTRETCH MOTOR CONTROL BOARD CALIBRATION
INSTRUCTIONS FOR 336-8/10 BOARD
Adjustments
Bias:
(RV3) The
RV3
pot controls the system bias.
This control injects an offset voltage that adds or subtracts from the voltage
reference defined by the External Tension Adjustment (Film Tension
Potentiometer). This will allow extremes of adjustment to be set to levels
consistent with proper operation. Typically, the bias will be used to center
the operating range in linear portion of its characteristics.
Note:
This adjustment is normally made at the factory and should not
require field adjustment. For reference, the factory test procedure calls for a
voltage setting of 1.3 volts DC at the cathode of Z1 (Zener Diode) achieved
by adjusting the
RV3
pot.
Span:
(RV1) The
RV1
pot controls the system loop gain.
The system loop gain may be adjusted if the motor continues to be energized
when the dancer arm is unloaded and at rest. With the machine stopped, the
pot should be adjusted to ensure that the motor is de-energized in this condition,
and so that a light pull on the free end of the film causes the film to feed freely.
CCW adjustment of this pot will increase the response time, in effect softening
the motor tension response plus decreasing the maximum motor speed attainable.
CW adjustment will decrease the response time, in effect sharpening the motor
response time plus increasing the maximum motor speed attainable.
Current Limit:
(RV4) The
RV4
pot controls the torque (amperage) that the 336
board will allow to the motor.
To protect the unit against damage should the motor stall, jam, or current demands
exceed its rating, a current limiting circuit is included which keeps motor current at