LG LMVM1935SB, Service Manual

Page: 27 / 46

7-15
TEST AND CHECKOUT PROCEDURES, AND TROUBLE SHOOTING
A. TEST PROCEDURES
- CAUTIONS -
- DISCONNECT THE POWER SUPPLY CORD
FROM THE WALL OUTLET WHENEVER
REMOVINGING THE CABINET FROM THE UNIT.
PROCEED WITH THE TESTS ONLY AFTER
DISCHARGING THE HIGH VOLTAGE CAPACITOR
AND REMOVING THE WIRE LEADS FROM THE
PRIMARY WINDING OF THE HIGH VOLTAGE
TRANSFORMER. (SEE FIGURE 24)
- ALL OPERATIONAL CHECKS WITH MICROWAVE
ENERGY MUST BE DONE WITH A LOAD (1 LITER
OF WATER IN CONTAINER) IN THE OVEN.
COMPONENTS TEST PROCEDURES RESULTS
NOTE: A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS
SERVICED FOR ANY REASON.
MAGNETRON
(Wire leads are
removed)
HIGH-VOLTAGE
TRANSFORMER
(Wire leads are
removed)
1) Measure the resistance: Across the
filament terminals of the magnetron
with an ohm-meter on Rx1 scale.
2) Measure the resistance: Between
each filament terminal of the
magnetron and the chassis ground
with an ohm-meter on high test scale.
1) Measure the resistance:
With an ohm-meter on Rx1 scale.
a. Primary winding;
b. Filament winding;
c. Secondary winding;
2) Measure the resistance:
With an ohm-meter on highest scale.
a. Primary winding to ground;
b. Filament winding to ground;
Normal reading:
Less than 1 ohm.
Normal reading:
Infinite ohms.
NOTE: Replace the magnetron, if the
magnetron checks and all of the
high voltage component tests are
good, but the unit still does not heat
a load.
Normal readings:
Approx. 0.2 to 0.5 ohm.
Less than 0.1 ohm.
Approx. 50 to 120 ohms.
Normal readings:
Infinite ohms.
Infinite ohms.
Primary
Winding
Secondary
Winding
Filament
Winding
Figure 24