GE JVM1790SK Service Manual - Page 26

TEST AND CHECKOUT PRECEDURES AND TROUBLESHOOTING - 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. Filament Winding Secondary Winding Primary Winding A. TEST PROCEDURES Figure 24 COMPONENTS TEST PROCEDURES RESULTS MAGNETRON (Wire leads are removed) 1. Remove wire leads. Install the magnetron seal in the correct position. Check that the seal is in good condition. 2. Measure resistance. (ohm meter scale:Rx1) • Filament terminal 3. Measure resistance. (ohm meter scale:Rx1000) • Filament to chassis 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. HIGH-VOLTAGE TRANSFORMER (Wire leads are removed) 1. Remove wire leads. 2. Measure resistance. (ohm meter scale: Rx1) • Primary winding • Secondary winding to ground • Filament winding 3. Measure resistance. (ohm meter scale: Rx1000) • Primary winding to ground • Filament winding to ground Normal(Approximately) 0.3 ~ 0.5 ohm 65 ~ 120 ohm Less than 0.2 ohm Normal readings: Infinite ohms. Infinite ohms. NOTE: A MICROWAVE ENERGY LEAKAGE TEST MUST ALWAYS BE PERFORMED WHEN THE UNIT IS SERVICED FOR ANY REASON. 7-15