Works great except loud buzzing

So so thought it was the diode replaced that.

It still heats food and water 1 cup in 60 seconds to boiling.

What's my next move ?

Capacitor ?

It's heating, so magnetron isn't the problem right?

Buzzing is constant soon as you start cook cycle starts within 3 seconds of pressing start.

Prior to this constant buzz it was only happening when magnetron was firing.

could tell because you'd see food or water boil when buzz was there .

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For example during a 4 minute or longer cook cycle. A year ago it would not begin buzzing within seconds of pressing start. It would only buzz when magnetron was hearing.