Pioneer VSX-921-K power supply crashed

[maxmat486]

hello everyone,
i've got a pioneer amplifier from the trash.
so i repaired it one time and it worked for one year. (i changed the top258MN AC/DC converter and a diode on the power supply).

but it crashed again, first, the fuse crashed, then, the fuse and the top258MN exactly at the same place . i'm looking for the schematic but i coudn't find it, i searched on
elektrotanya.com/pioneer_vsx-521_821_921-k_sm.pdf/download.html#dl
but i didn't find it ... any idea please ?

[m k]

Are you sure the type is correct?
ifixit has a manual, but it doesn't have a SMPS PCB.

PCB number on left of 2nd pic is not clear, what is it?

[maxmat486]

hello, thanks for helping, yes the type is correct, the PCB number is 70-28-07032-201-1S

[m k]

Yes, 7028 is clearly a correct prefix and I also found a manual were almost exact board is mentioned, but no pictures.
With luck the same board is used in some other 230V machine.

But it's also pretty simple, maybe you can draw some sort of a schematics by your self.

Top right of 2nd picture is input and line filter.
Top center is main bridge and left of it is reservoir capacitor.
Between reservoir capacitor and main transformer is a switcher chip.
S-W corner of main transformer is possibly a feedback opto.
Then bottom center has secondary regulator and its reservoir capacitors.
Under black ribbon cable are possibly some voltage writings beside a connector.

Secondary side can overload the main transformer, but it shouldn't blow the switcher, like seems to be the case.
A resistor bit up from the switcher in first picture seems to be gone also.