With Power on and Thermocouple

	Control transformer	Check for 208/240VAC supply to the primary of the
		control transformer. If no voltage is present, trace
		wiring back to the main power switch. If voltage is
		present, check for 24VAC at the transformer
		secondary. If there is primary voltage, but no secondary
		voltage, replace the control transformer.
	Oven control	Check for 24VAC supply to control. If no voltage is
		present, trace wiring back to control transformer. If
		24VAC is present, check for a read-out on the display.
		If there is 24VAC supplied, but there is no read-out on
		the control display, replace the oven control.
		If there is a read-out on the control, set the control to
		maximum temperature (see installation operations
		manual for temperature adjustment). With the control
		set at maximum temperature, check for supply voltage
		to the oven control at terminals J3-12 and J3-3. If there
		is no voltage present, trace wiring back to the air
		pressure switch. If there is voltage present, check for
		output voltage at the Main heater relay (R1). If there is
		voltage at the Main heater relay, proceed to “Main
		heater relay” for next check. If there is no voltage at the
		Main heater relay, trace wiring back to the oven control.
		If there is no voltage output at the oven control, check
		the read-out on the control. If the control reads
		“PROBE FAIL”, this indicates that the thermocouple
		has failed or become disconnected from the oven
		control.
	Thermocouple	Check to be sure that the thermocouple is securely
		connected to the oven control. If the thermocouple is
		connected to the oven control, and the control indicates
		“PROBE FAIL”, disconnect the thermocouple from the
		oven control and measure the resistance of the
		thermocouple. The thermocouple should read approx.
		11Ω. If these readings are not achieved, replace the
		thermocouple. If these readings are correct, proceed.
	Oven control	If the thermocouple checks good, but the oven control
		display indicates that there is a thermocouple failure,
		replace the oven control. If the oven control indicates a
		temperature reading but the oven will not heat,
		proceed.
	Thermocouple	WITH POWER ON AND THERMOCOUPLE
		ATTACHED TO THE OVEN CONTROL: Measure the
		DC millivolt output of the thermocouple. Refer to the
		thermocouple chart (located in the “Removal” section of
		the manual) for proper millivolt readings. If these
		readings are not achieved, replace thermocouple.
	Oven control	If the thermocouple checks good, but there is no
		voltage output to the Main heater relay, replace the
		oven control. If there is voltage output to the Main
		heater relay, proceed.
	Main heater relay	Check for supply voltage to the relay coil. If voltage is
		present and the relay will not activate, replace the Main
		heater relay. Also check each relay contact for high
		voltage input and output.
	Heating element(s)	Check the Amp draw on each power leg for proper
		load. Check the specification plate for rating
		information. If the amp draw is high or low, check the
		individual elements for opens, shorts and proper
		resistance.
		WITH POWER OFF: To check resistance of the
		elements, remove all leads from the elements and use

DTF – 1920 Series Service Manual