I have two scx-5935's in the shop
#1 The display keeps cycling Samsung, Samsung, all day long.
#2 Machine boots up for an instant and then the display goes blank. Does anyone have any thoughts?

Have you tried flashing the firmware, Samsung is notorious for corrupted firmware.

Next I would go for the main engine controller pcb, or power supply pcb.

In our experience with Samsung those are the most common failures that exhibt the symtoms you describe.

So far the SCX-5935's have been behaving well, but had lots of similar failures with the SCX-4828's. I did not have 1 customer keep thier 4828 for more than a year.

Good Luck

Swapping the hard drive fixed the number two machine. Now i'm going to format the bad hard drive and see if that will work.

I tried to do a firmware up grade on machine one, but it won't take because of its issues.

Thanks for your imput