DC Gearmotor
Time/Temp Display | 12.6 VAC Power |
inoperative | Supply |
S/N 2011821 & Above
Refer to Page 45
Temp Display out or | NOTE: Time/Temp displays |
erratic | uses two types of temperature |
| sensor, Thermistor Probe - |
| 2 yellow wires, Thermo- |
| couple Probe - 1 red wire |
| and 1 white wire |
| Thermistor Probe |
Thermocouple Probe
changing a board or tach. This test is not always 100% accurate as this test is not performed at operating speeds. However, this test is the best method currently available. Readjustment should always be attempted at least once before replace- ment. See procedure for board adjustment in Section D.
If the problem seems to be the motor or gearbox. Check the brushes in the motor for excessive arcing and/or unusual wear. Check the motor and gearbox from instructions located under “possible cause” listing “Conveyor gear motor”. Measure the transformer primary
for a nominal 120 VAC input.
If 120 VAC primary voltage is not available, refer to the schematic and trace the circuit for incomi ng power failure
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. The older units have a 4 amp ambient fuse in each red secondary lead. These may be jumpered to determine if they are burnt out or intermittent.
Insert the thermocouple of your pyrometer into a finger hole in the top center of the oven. The thermocouple tip should measure air temperature and must not be touching metal. Disconnect the yellow tipped thermistor leads from the time/temp. terminals 9 &10 Measure the resistance of the thermistor probe See the chart in Section D for proper
resistance readings. Inspect the thermistor bulb for itsproper location in its spring holder.Check for short in leads where they enter the sensor bulb. Also check each thermistor lead for short toground. Connect temperature meter to thermocouple at terminals 9 and 10 on back of the time/temp display. (Be sure tomaintain proper polarity on therocouple connections.) Compare actual oventemperature with the reading at the time/temp display. If the temperature readings match,
32 | Impinger II - 1100 Series Service Manual - International |
