In sci.electronics.repair, on Sat, 3 Dec 2016 03:08:33 -0800 (PST),
wrote:

On Wednesday, November 30, 2016 at 6:57:50 PM UTC-5, tom wrote:
"Jon Elson" wrote in message
...
micky wrote:

How long does it take a microwave oven to warm up?

The heater in the magnetron tube takes a couple seconds to warm to the
point
where it will emit electrons. You can hear it easily on the old
transformer
microwaves, the fan starts and it begins to hum, then a couple seconds
later
the hum gets much louder. That louder hum is when the magnetron tube
starts
conducting.

Newer microwaves with switching power supplies may delay turning on the HV
until the heater has warmed up, and they may not have that transformer
hum,
so it may be harder to tell when the RF comes on.

Jon

Stick an old CD in the MW and you can see exactly when the RF power starts.


I tried that with one of my wife's Kenny G CDs. A few seconds in the MW improved it immensely.

I have a 45 rpm record someone must have left in the sun. Seen from the
side, it's one long sine wave, going around in a circle, and the
amplitude is an inch and half.

I'm trying to find a record player with a 2-inch needle so I can play
it.