Repair guides
Pick a type, an appliance or a brand. Every guide lists the tools, the safety call-outs, the steps and the reading you should expect.
Diagnostic · 374
Symptom → most likely cause, step by step
Component tests · 69
How to test a specific part, with expected readings
Installation · 33
Install, replace and hook up appliances correctly
Fundamentals · 24
Core skills every appliance tech uses
Appliance
Brand-specific guides
4 guides · Microwaves
Component tests · 4
Component test · MicrowaveMagnetron: filament and filament-to-case tests (microwave)
The magnetron turns high voltage into microwave energy. An ohmmeter can catch an open filament or a filament shorted to the case, but it cannot prove the tube makes full power. Rule out the HV diode, capacitor and transformer before ordering a magnetron.
Component test · MicrowaveMicrowave high-voltage diode test
The HV diode works with the HV capacitor to double the transformer voltage for the magnetron. It is made of many junctions in series, so an ordinary meter only shows it is not shorted. A shorted diode is a classic cause of no heat with a loud hum.
Component test · MicrowaveMicrowave high-voltage transformer windings
The HV transformer has a primary, a high-voltage secondary and a low-voltage filament winding. Resistance checks find opens and shorts to the core; turn-to-turn shorts may still need a known-good comparison.
Component test · MicrowaveMicrowave HV capacitor and bleeder resistor
The HV capacitor has a built-in bleeder resistor meant to drain its charge, but bleeders fail, so always discharge by hand. A shorted capacitor blows the HV fuse immediately. Resistance tests catch shorts; a capacitance reading is better.