Conventionally the corner pins (on a 14 pin device, for example, pin 14 is +5V, pin 7 is ground). But there are exceptions. A TTL databook, or a way of reading the data sheets on-line is almost essential :-) The power distribution arrangements are shown on page 11 of that pdf manual I mentioned : http://www.bitsavers.org/pdf/dec/pdp11/1124/MP01018_1124schem_Aug80.pdf Look at the '11/24 Power Distribution BD' part of the schematic. There's a +5V line coming from the PSU and ending up on pins 1 and 4 of the backplane sockets and a separate +5VB going to pin 12 of those sockets. Of course you need to fix the PSU before you can start sorting that out. -tony -------------------------------------------------------------------- mail2web LIVE ? Free email based on Microsoft? Exchange technology - http://link.mail2web.com/LIVE