THis family of machines (DECmate/Pro/Rainbow) are very easy to strip down into FRUs, and almost impossible to repair, inm that it's very hard to conenct them up unmless everythign is in the right place in the case. But anyway, from, what I rememebr.... You start by taking the end cover off the cardcage. Then unplug all the cables fro mteh top of the PCBs -- some go to the drives, there may be a jumber cable ewbtween 2 video boards, etc). Then pull out the plastic tab handle on a PCB as far as it ill go and turn it (I think anticlockwise) by 1/4 of a turn. THis will spred the conenctor contacts, the boards then side out of the end of the cardcage. With the PSU and drives removed (the latter slide out frontwards, there's spring tab in the usual way),you'll see a number othumbscrews along the chasiss flange in front of the cardcage (IIRC). Loosen these off a bit at a time untill they're all free, then the motherbvoard sildes out towards the back of the machine I think the rest of it is obvious. I think it's a standard DPST rocker switch. I suspect anything rated for mains that will fit in the hole will work. Ouch!. Modifications were not uncommon,but it sounds like yours has been got at ;-( Last time I worked on one of these suppleis I needed a tamperproof torx driver to get one of the PCB fixing screws out. Did you? If not, it's a fair sign somebody has been there before you. -tony