Can't help with schematic, but I had the top off one recently because it gave up after about a minute.
However I can tell you there is a 'primary' and 'secondary' circuit. because just under the top is a 'relay'.as well as a 'timer' and switches.
If you remove the panel on the rear you will see the motor/fan and the heating elements on the secondary circuit.
So you should be able to test the elements and replace as necessary.
My problem was not the same as yours but you may find it of interest.
I removed the relay and when tested with continuity meter it was OK.
I then rigged it up for a 'live' test and when switched on again it was OK, but I left it on and after about a minute or so it failed. I tried it again after it had time to cool a little and it was OK again. Leaving it on for longer periods it went off and on as the coil heated and cooled.
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