Weller WES51 ground issues

[AmssmA]

Hi

My soldering station is a Weller WES51 for a long time.
Today the station died, the LED didn't turn on and the tip doesn't heat.

I opened the station and checked the transformer power switch and voltages in the controller board. Everything appears to be ok.

When i tried to verify the clock in the micro controller (PIC) and touch the oscilloscope ground probe in the common of the controller  the station works.

If i connect the transformer core (that is grounded) to one of the secondary outputs the station works(as you can see in one of the attachent pictures).

There is continuity between the tip of the  station and the ground terminal.

Any ideas why this is happening?

Thanks.