Steve B wrote:

My DIL has a bake oven with a combo microwave. The microwave died, and the
repair guy said that the microwave couldn't be fixed. I find that hard to
believe. The unit is not that old. Are there things in a microwave that go
out that one just absolutely cannot repair?

In a microwave-only oven, yes, because repair is more expensive than a
whole oven, but in a convection-microwave, I think only a broken oven
cavity (has anybody taken a sledge hammer to it recently?) or a bad
high voltage transformer can make repair uneconomical. BTW if this
is a table top model, L-G makes one for GE and also for Sears, the
differences being price and one having a touch panel while the other
having regular buttons.

A microwave oven consists of a fan-cooled magnatron powered by a high
voltage doubler (capacitor, diode), connected to a high voltage
transformer, connected to some control circuitry (simple relay or
inverter) and the 120VAC. There's probably also a high temperature
cutoff for the magnatron. Magnatrons cost as little as $30, the high
voltage capacitor and diode maybe $20-30 for both, and my parents have
a 30-year-old convection/microwave oven that's been fixed 3-4 times by
replacing those components plus the hi-temp cutoff. Also ovens with
touch panels may wear out their buttons or develop cracked solder
joints from flexing too much. If your oven buzzed briefly just before
quitting, there's a good chance the diode shorted.

www.repairFAQ.org has lots of repair information, including safety
information. Microwave ovens can electrocute (kill) you even when
unplugged, because of that big capacitor, whose built-in bleeder
resistor sometimes cracks and doesn't bleed down the 2,000 volts.