Lincoln 1100 Series Service Manual page 29

STEPPER MOTOR DRIVE
Conveyor will not run
Time/Temp Display
inoperative
Temp display out or
inaccurate
Impinger II –1100 Series Service Manual - Domestic
Conveyor Switch
Conveyor Fuse 3AMP
Fuseholder Conveyor Control
(Stepper) Transformer
Speed Adjustment
Potentiometer
Conveyor Motor (Stepper)
Control
Conveyor Drive (Stepper)
Motor
12 VAC Power Supply
(Transformer)
Time/Temp Display
NOTE: Time/Temp displays
use two types of temperature
sensors thermistor probe-2
yellow wires thermocouple
probe probe-1 red wire and 1
white wire
Thermistor Probe
Check for 120 VAC to conveyor switch. If no voltage is
present, trace wiring back to the oven power source.
WITH POWER OFF: Check continuity between switch
terminals.
Check, replace if necessary. (Not used on Model 1151)
Check, replace if necessary. Check for 120 VAC supply
to primary of transformer, if voltage is not present, trace
wiring back to the fuseholder. If voltage is present,
check for output voltage from the transformer
secondary. NOTE: This control transformer outputs (2)
secondary voltages. Red Leads 29 VAC Brown Leads
10 VAC If BOTH secondary voltages are not present,
replace the transformer.
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
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.
NOTE: if the conveyor drive motor becomes jammed,
the motor will stop turning. To reset, turn off conveyor
switch, wait 10 seconds and turn the conveyor switch
on. If the motor does not run, check for 2 to 29 VAC
across the motor terminals 1 to 2 and 3 to 5 on the
conveyor motor control. If voltage is not present at both
sets of terminals, replace control.
Check the drive sprocket on motor output shaft to insure
that it is tight. WITH POWER OFF: Turn the motor shaft
to check for jammed gear box. Check motor windings.
Ohm readings on motor terminal -1-5, 2-6, 3-7, 4-8,
each reading should be approximately 2 ohms. If motor
shaft will not turn, replace conveyor drive (stepper)
motor.
Measure the transformer primary for a nominal 120 VAC
input, if voltage is not present, trace wiring back to the
oven power source. Measure the secondary output,
which will normally be 12-15 VAC. Voltage across
terminals 1 and 3 on the time/temp. display should read
12-15 VAC. Terminals 1-2 and 2-3 should be 1/2 the
voltage reading to 1-3. If the above secondary readings
are not achieved, replace transformer.
If proper voltage is present at terminals 1, 2, and 3 on
time/temp display, but the display is not lighted, recheck
all connections for tightness. If time/temp display is still
not operating, replace the time/temp display
Place the thermocouple of a pyrometer into the center of
the top finger. Be sure the tip of the thermocouple is not
touching metal. The pyrometer will indicate oven
temperature.
Disconnect the thermistor probe leads from the
5%
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