On Wed, 24 Sep 2008 19:31:52 -0700 (PDT), poster
put finger to keyboard and composed:

http://geocities.com/anglomont/mw.jpg

What is actually the curved line close to the transformer and
directly connected to magnetron?

That's the transformer winding that supplies 3VAC to the magnetron's
filament.

What if upon disconnecting the both diodes fast fuse blows again
when either microwave or grill cooking is started?

According to Sam's Microwave FAQ ...

"An open HV diode will result in AC instead of DC across the magnetron
with a peak negative value (the only one that matters) about 1/2 of
what it should be. The result will likely be little or no detectable
heat but no other symptoms".

If the fuse blows again, then I'd be looking at the power transformer
or the magnetron.

What is it exactly connected between a8-a7?

That's the transformer (and metal oxide varistor) that is part of the
low voltage DC supply for the control board. One secondary winding
supplies the +5V (?) logic, the other probably supplies the display
filament.

- Franc Zabkar
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