Duke DSO 500, Service Manual, Page: 49 / 80

49
COMPONENT TESTING
HIGH VOLTAGE CAPACITOR TEST
WARNING
THE HIGH VOLTAGES AND CURRENTS AT
THE FILAMENT AND SECONDARY WINDING
OF THE TRANSFORMER ARE EXTREMELY
DANGEROUS. NEVER MAKE ANY DIRECT
VOLTAGE OR CURRENT MEASUREMENTS
AT THESE WINDING. IT IS VERY DANGER-
OUS TO WORK NEAR THIS PART WHEN
THE OVEN IS ON, OR IF THIS CIRCUITRY
HAS BEEN SWITCHED OFF.
WARNING
THE HIGH VOLTAGE CAPACITOR RETAINS
THE 2.5 kVDC CHARGE EVEN AFTER THE
OVEN IS DISCONNECTED. THIS CAPACI-
TOR MUST BE DISCHARGED BEFORE
WORKING ON ANY COMPONENTS IN THE
HIGH VOLTAGE AREA.
WARNING
THE HIGH VOLTAGE CAPACITOR HAS HIGH
VOLTAGES PRESENT AT ALL TIMES EVEN
IF THE OVEN IS NOT COOKING. BE SURE
THE OVEN IS ISOLATED BEFORE TESTING.
REFER TO THE SAFETY PRECAUTIONS AT
THE FRONT OF THIS MANUAL.
Tools required
• Digital Multimeter
• Megohmmeter
Test Procedure
1. Disconnect the oven from the power
source.
2. Remove top cover and right side panel to
access the high voltage capacitor.
WARNING
HIGH VOLTAGE CAPACITOR MUST BE
DISCHARGED BEFORE PERFORMING
THIS PROCEDURE. WAIT AT LEAST FIVE
(5) MINUTES AFTER SHUTDOWN OF HIGH
VOLTAGE SYSTEM.
3. Discharge the high voltage capacitor as
described in the paragraph DISCHARGING
THE HIGH VOLTAGE SYSTEM ON THE
DUKE SPEED OVEN.
4. Ensure that the High Voltage Capacitor is fully
discharged before commencing work.
5. Remove all connections from the High
Voltage Capacitor.
6. Using a digital multimeter, check between
capacitor terminals & compare results with
the following:
a. Pass if approximately 10 Megohms:
b. Pass if open circuit between terminals and
case.
7. Using a Megger, test the insulation resistance
between the terminals and the case.
Resistance should exceed 100 Megohms.