Lincoln Impringer Conveyor Oven 1200 - Manual (Page 36)

Impinger I -–1000 Series Service Manual - International 36
Speed Adjustment
Potentiometer This is a 0 to 50k ohm, 10 turn potentiometer.
WITH POWER OFF: remove the 3-pin
potentiometer cable plug from the motor control
board. With a digital multimeter, check the ohm
reading across the red lead to the black lead. This
reading should be 50k ohms ±5% as the
potentiometer is rotated through its 10-turn rotation.
Place the meter leads on the red lead and white
lead. Rotating the potentiometer slowly, from low to
high, the meter should show an even transition
from 0 to 50k ohms ±5% through the 10-turn
rotation of the potentiometer. There should be no
dead or open spots through the 10 turns of the
potentiometer. Check all three leads to ground.
There should be no continuity to ground. If any of
the above checks fail, replace the potentiometer.
Conveyor Motor
(Stepper)Control NOTE: if the conveyor drive motor becomes
jammed or begins to run at an uncontrolled speed,
the conveyor motor will stop running. To reset, turn
off the conveyor switch, wait 10 seconds, turn the
conveyor switch on. If the motor does not run after
attempting re-set, check for 2 to 29 VAC across the
motor terminal 1 to 2 and 3 to 5 on the conveyor
motor control. If voltage is not present at both sets
of terminals, replace control.
Conveyor Drive
(Stepper)Motor Check the drive sprocket on motor output shaft to
insure that is tight. Check motor windings;
measurements should be approximately 2 ohms.
Terminal 1-5, 2-6, 3-7, 4-8. WITH POWER OFF:
Turn the motor shaft to check for jammed gear box.
If motor shaft will not turn, replace conveyor
drive(stepper) motor.
Time/Temp Display
inoperative 12.6 VAC Power Supply Measure the transformer primary for a nominal 120
VAC input. Measure the secondary voltage output
which will be 12.5 to 15 VAC normally. Recheck
secondary output at rear of Time/Temp Display.
Terminals 1 to 3 should read 12.5 to 15 VAC.
Terminals 1 to 2 and 2 to 3 should be 1/2 of the
reading across 1 to 3. If you do not get the above
secondary readings, replace the transformer. If 120
VAC primary voltage is not available, refer to the
schematic and trace circuit for incoming power
failure. There is a 4-amp fuse in each red
secondary lead. These may be jumpered (for test
only) to determine if they are defective or
intermittent.
NOTE (Dual Belt Ovens) Dual belt ovens utilize a double pole double throw
switch, which allows either of the optical encoders
to be read from a single Time/Temp. Display.
Check the switch and replace as needed.
Temp Display out or
inaccurate NOTE: Time/Temp displays
use two types of temperature
sensor, Thermistor Probe - 2
yellow wires, Thermocouple
Probe - 1 red wire and 1
white wire Place your pyrometer thermocouple into the center
between fingers T2 and T3 in the oven. Disconnect
the yellow tipped thermistor leads from the
time/temp. terminals 9 and 10. Measure the
resistance of the thermistor probe.
Thermistor Probe See chart on page 72 for proper resistance
readings. Inspect the thermistor bulb for its proper
location in its spring holder. Check for shorts in
leads where they enter the sensor bulb. Also check
each thermistor lead for short to ground.