The fluke 3330B, the reason the output is not latching is probably the electrolytics on the current limit board, at least that's what was wrong with mine. Pretty much every electrolytic is bad.
If you want to get people to drool a little more, check the voltage coming out of the zener reference board, it's in the left row of boards (looking from the front) and has two 2mm banana jack's, red and black, on top to verify the 10V output, perfect for some multimeter probes...
Also, just to check, but you did press down the security switches on the top and bottom of the case (normally held down by the case)? They also prevent you entering OPR