Thnaks a lot!!! I'll do that.))

:) ...Here is what I have found:
1. H.V. transformer has ~120VAC on primary side, resistance is within a normal range,lesss than 0,5ohmm, due to a thick wire diametr of a cupper wire used in primary winding.
2. When power has been applied to unit and secondart and filament winding are disconnected from circuits( ground, h.v.diode,h.v.capacitor, magnetron, e.t.c.) transformer still maked loud noise, but less loud, when all h.v. transformer winding wires connected to circuits. That tell me, I have a defective h.v.transformer.
3. When I checked a resistance between a socondary winding and a ground pont( a trnasfomer core case, or unit chassis) resistamce on my multimetr is 72 ohm( R=72ohm), which is low. Normaly a secondary winding aproximately has a resistanse of 100 ohms, but in my case it doesn't. So, I think I have a defective transformer! Bingo!!!:)
I want to thank you for all advices you have been given!!! I am apreciate that!!!:)
...Now I need to replace a h.v. transformer to see, if I have any other surprises!!!:) ...I hope not!!!:)

...I haven't replaced a magnetron yet...No need at this point...until I find out what is going on in this microwave oven...
...I replaced a high voltage(h.v.) transformer, but it didn't help...I still have the same loud sound comming from oven, when unit works. I need a further evaluation...It act, as a defective magnetron, or h.v.transformer, but that isn't the case....H.v. diode and h.v. capacitor are ok. It makes a loud souns, when only primary winding of a h.v. transformer connected to circuit and all high voltage componets are disonnected...Something going on on primary die of circuit...A line filter cheks ok...fan capacitor cheks ok...I know, PCB can't couse a loud sound in unit, if a h.v. transformer has ~120V on it's primary winding. All thermistors in unit cheks OK also...It means something else...What is it?