Sounds like the invertor feed (24v) isn't being generated...
Often there is a seperate switch mode supply independant of the rest of the psu ..to generate the 24v ..
You say there is no longer a short on the 24v line after the double diode ..
Does this double diode read as a diode ..or does it read dead short left pin to centre ..and right pin to center ....when removed ...
If so its faulty ...
If it reads ok ..ie ..as A diode should ..
Low resistance one direction ..high resistance the other ...
Then I suspect the switch mode chip driving the transformer ..to generate the invertor supply to be non functional..
Its then a case of sourcing the switch mode surface mount chip ..and repacing ...plus its ascociated power FET ...or ...sourcing a new psu board ...which might be easier..
good luck ..
Evan
