Pratica Copa Express, Service Manual

Page: 72 / 130

66
MICROWAVE SYSTEM
Testing Primary Winding (208V/220V/240V)
1) Remove the rear panel from the unit.
2) Unplug the oven and wait 5 minutes for the high
voltage capacitor to discharge or discharge manually by
grounding each capacitor terminal.
3)
Unplug the wires from the HV transformer terminals.
4) With an ohmmeter, measure the resistance across the
terminals of the primary as shown in picture on the right.
5)
The measured resistance value should be 0.6 ohms to
208/220V and 0.7 to 240V.
•
If the ohm reading is open or very high, replace the transformer.
Testing Filament Winding (3.6V)
1) Remove the rear panel from the unit.
2) Unplug the oven and wait 5 minutes for the high
voltage capacitor to discharge or discharge manually by
grounding each capacitor terminal.
3)
Unplug all the wires from the HV transformer
terminals.
4)
With the ohmmeter, measure the resistance across
the filament wires as shown in the picture on the right.
5)
The measured resistance value should be 0.0 ohms or
a very low reading.
•
If the ohm reading is open or very high, replace
the transformer.
Testing Secondary HV Winding (2000V)
1) Remove the rear panel from the unit.
2) Unplug the oven and wait 5 minutes for the high
voltage capacitor to discharge or discharge manually by
grounding each capacitor terminal.
3)
Unplug all wires from the HV transformer terminals.
4) With an ohmmeter, measure the resistance across the
secondary terminal and ground as shown in the picture on
the right.
5)
The measured resistance value should be 50 ohms.
•
If the ohm reading is very low, very high, or open,
the replace the transformer.