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DTF – 1920 Series Service Manual
9
Switch, Main Power WITH POWER OFF: Check continuity between switch
terminals. Replace switch as needed.
Control transformer Check for supply voltage to the primary of the control
transformer. If no voltage is present, trace wiring back
to the oven power relay. If voltage is present, check for
24 VAC at the transformer secondary. If there is
primary voltage but no secondary voltage, replace
control transformer.
Air pressure switch Check for 208/240VAC to the air pressure switch. If no
voltage is present, trace wiring back to main power
switch. This normally open switch should close when
the main fan is activated. Refer to the “Removal and
installation” section for proper adjustment. Replace as
needed.
Switch, Infrared heater Check for 208/240VAC to the Infrared heater switch. If
no voltage is present, trace wiring back to the air
pressure switch. WITH POWER OFF: Check continuity
between switch terminals. Replace switch as needed.
Conveyor motor Check for supply voltage to the conveyor motor. If no
voltage is present, trace wiring back to the primary of
the control transformer. If voltage is present and the
motor will not run, check the motor windings for opens
or shorts.
WITH POWER OFF: Check the motor windings as
follows:
Grey to black - 236 ohms approx.
Grey to brown - 236 ohms approx.
Brown to black - 472 ohms approx.
If any of the above fails, replace conveyor motor.
Capacitor, conveyor motor Check for shorts or grounds. Replace capacitor as
needed.
WARNING: Capacitor has a stored charge, discharge
before testing.
Switch, conveyor reversing Check continuity between switch terminals. Replace
switch as needed.
Oven control If there is supply voltage to the motor, and the motor,
motor capacitor, and reversing switch check good,
replace the oven control.
Conveyor motor runs, but there
is no speed display
Oven control Check for output voltage from oven control to hall effect
sensor (sensor is located in conveyor motor). Measure
voltage at the motor connector, red wire and yellow
wire. Voltage should be approx. 10VDC. If no voltage is
present, trace wiring back to oven control. If there is no
voltage present at the oven control, replace the oven
control.
Conveyor motor If there is voltage supplied to the hall effect sensor,
check for a frequency output from the hall effect
sensor. Measure frequency across the yellow and white
wires at the motor connector. Frequency reading
should be approx. 25 – 100 Hz. If these readings are
not achieved, replace conveyor motor. If the readings
are achieved, proceed.
Oven control If the hall effect sensor readings are correct, but there
is no speed indicated on the display, replace the oven
control.