Kuppersbusch MW 800.0, Service Manual

Page: 25 / 39

Service Manual MWG 1000 25
Only for internal use
4.1.2 Checking the capacitor
If the capacitor has an open flow of current, then the magnetron is not under high voltage.
If there is a short circuit in the capacitor, this will result in the mains fuse blowing due to the consumption
of peak current.
The open or short-circuited capacitor can be tested with an ohmmeter.
♦
Disconnect the appliance from the mains.
Discharge the capacitor.
Disconnect the leads of the capacitor.
♦
The resistance between terminal “C” and the other terminal is
measured using an ohmmeter set to the highest range.
The indicator should shoot up briefly, indicating continuity and
then point towards infinite when the capacitor is charged. This
reading should also appear if the measuring sensors are
swapped over.
♦
If the ohmmeter indicates continuity between the terminals of the
capacitor or if it shows no fluctuations the capacitor must be
exchanged.
4.1.3 Testing the high-voltage diode
The high-voltage diode is no longer accommodated in the case of the capacitor. It is located outside the
case. The high-voltage diode is installed in the same way as the high-voltage capacitor.
It can prove difficult to check the operation of the diode with a normal ohmmeter. If the ohmmeter points
towards infinite, then you should not come to the conclusion that the diode is defective. It is when a
resistance is measured in both directions that the diode is defective.
Note : Using different ohmmeters for the measurements will produce varying results. We therefore
recommend that you first test the measuring instrument on a diode that is in order before carrying
out any further tests on other diodes.