Moonraker writes:

Model number NN-V659 has gone kaput. The instructions say it must only
be replaced by a qualified engineer. Surely it cannot be that difficult,
is it just a safety matter?

As another poster has said, microwaves and combination ovens contain a
large high voltage capacitor; usually in a metal can with push-fit
terminals and with an internal bleed resistor, which could perhaps fail
unless the dielectric material itself is the resistor (by being
intentionally just a little bit electrically leaky; don't know if they
could do that with modern materials but it would be a clever way to
make the thing safer).

The voltage on the capacitor is *very* high, and so is the power
(obviously).
Most magnetrons want 20,000 or 30,000 volts from what I've seen, and in
the circuit they use, about half that voltage will be developed across
the capacitor.
If the unit was turned on momentarily without giving the magnetron
filament enough time to heat up, the capacitor wouldn't be discharged
by the magnetron.

You most definitely don't want to poke around inside the case with the
power on, and you should always use a highly insulated probe to short
across the terminals of the capacitor if there's any risk that it still
holds a charge, which it could do for a long time if no discharge
resistor existed.

Changing the bulb is not much more difficult than changing an ordinary
light bulb. Some replacements may have been designed to withstand a bit
of vibration, I've heard, so you want the correct bulb.
Some have push-fit terminals and ISTR that some have simple SES bases
(small screw-in); others are special designs.

Any tips, also source of spare lamp and
type/rating. I don't want to take it apart to find the details then
re-assemble only to take apart a little later to replace it.

You'll probably have to do that anyway, but taking the case off isn't
all that hard on the units I've looked at. Maybe a dozen self-tapping
screws.
What you DO NOT want to do is to touch anything inside until you're
ABSOLUTELY sure it's safe to do so. I have no doubt at all that a good
few people have been thoroughly fried by microwave high voltages.

Spares can be found in the usual ways. Usually over-priced.

--
Windmill, Use t m i l l
@ O n e t e l
. c o m