Has someone been in there before? That 600V 0.02uF Sprague Orange Drop capacitor is frequently used as a coupling capacitor in tube amps and looks out of place.
I'd replace all the parts on the blackened part of the circuit board. The one resistor looks like an 8.5K 2W carbon composition but could be replaced with a metal oxide power resistor. The white ceramic resistor looks like a 5W 1.5K which should be easy to find. If the blue trimmer is not totally fried, you could measure the resistance; otherwise check for some other identifying marks.
mouser.com and allied.com should have the parts needed. If you are compulsive, you could replace all the components and make a like-new circuit board : http://www.apug.org/forums/viewpost.php?p=767799
In reality, it would be easier to just locate a new 24V power supply. The power supply I rebuilt also contained all the control functions for the servo motors in a closed loop head; therefore totally irreplaceable.