Safe discharging of the high voltage capacitor in a Microwave
It is essential - for your safety and to prevent damage to the device under test as well as your test equipment - that the large high voltage capacitor in the microwave generator be fully discharged before touching anything or making measurements. While these are supposed to include internal bleeder resistors, these can fail. In any case, several minutes may be required for the voltage to drop to negligible levels.
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The technique I recommend is to use a high wattage resistor of about 5 to 50 ohms/V of the working voltage of the capacitor. This will prevent the arc-welding associated with screwdriver discharge but will have a short enough time constant so that the capacitor will drop to a low voltage in at most a few seconds (dependent of course on the RC time constant and its original voltage).
•    For the high voltage capacitor in a microwave oven, use a 100K ohm resistor rated at least 5 kilovolts and several watts for your discharge widget, with a clip lead to the chassis. As a practical matter, a single resistor like this will be hard to find. So, make one up from a series string of 10 to 20 1/2 W or 1 W normal resistor.
The reason for specifying the resistor in this way is for voltage hold-off. Common resistors only are rated for 200 to 500 V, but there may be as much as 5 kV on the HV cap. You don't want the HV zapping across the terminals of the resistor. Special high voltage resistors are available but they are expensive and not readily available from common electronics distributors.

.•    Clip the ground wire to an unpainted spot on the chassis. Use the discharge probe on each side of the capacitor in turn for a second or two. Since the time constant RC is about .1 second, this should drain the charge quickly and safely.
•    Then, confirm with a WELL INSULATED screwdriver across the capacitor terminals. If there is a big spark, you will know that somehow, your original attempt was less than entirely successful. There is a very slight chance the capacitor could be damaged by the uncontrolled discharge but at least there will be no danger.
•    Finally, it is a good idea to put a clip lead across the capacitor terminals just to be sure it stays fully discharged while you are working in the area. Yes, capacitors have been known to spontaneously regain some charge. At worst, you will blow the fuse upon powering up if you forget to remove it.
WARNING: DO NOT use a DMM for checking voltage on the capacitor unless you have a proper high voltage probe. If your discharging did not work, you may blow everything - including yourself.
A suitable discharge tool can be made as follows:
•    Solder one end of the appropriate size resistor (100K ohms, 25W in this case, or a series string of smaller resistors) to a well insulated clip lead about 2 to 3 feet long. Don't just wrap it around - this connection must be secure for safety reasons.
•    Solder the other end of the resistor to a well insulated contact point such as a 2 inch length of bare #14 copper wire mounted on the end of a 2 foot piece of PVC or Plexiglas rod which will act as an extension handle.
•    Secure the resistor to the insulating rod with some plastic electrical tape.
This discharge tool will keep you safely clear of the danger area. The capacitor discharge indicator circuit described in the document: Capacitor Testing, Safe Discharging and Other Related Information can be built into the discharge tool if desired.
Again, always double check with a reliable high voltage meter or by shorting with an insulated screwdriver!
Reasons to use a resistor and not a screwdriver to discharge capacitors:
1.    It will not destroy screwdrivers and capacitor terminals.
2.    It will not damage the capacitor (due to the current pulse).
3.    It will reduce your spouse's stress level in not having to hear those scary snaps and crackles