PDP-11/34 PSU Yet Again

Well, I finally got around to testing the PSU on my 11/34. I measured at the backplane connectors with no backplanes plugged in. Everything checks out except for the -5V and +20V. Accordingly, the LED at the bottom of the H745 brick (regulator 1) does not light. However, some of the other voltages coming from the H745 (according to the BA11-K FMPS) seem to be OK. Does anything in the machine even need -5V or +20V? If not, can I leave the bad brick in place? I have: KD11-EA, KY11-LB, DL11-W, MS11-JP, M7850 parity, DZ11-A, RK11-D. I'll be adding a RX11 at some point. Someone enlighten me, please. :-) I'm pretty sure I have a spare brick. Also: what are these signals on the 6-pin backplane mate-n-locks? - AC LO - DC LO Something I learned: If you have a H785 brick in your 11/34 BA11-KA cabinet, ignore what the 11/34 and KY11-LB manuals say about battery backup and the rotary power switch. You can indeed have a battery backup with a BA11-K, and the switch on the KY11-LB works as you think it should. You must connect the ribbon cable from the H785 to the corresponding connector on the KY11-LB, or the H785 won't work. You must NOT connect the one-wire connector from the H785 to P4(?) of the AC input box, or else your machine won't turn off, regardless of the rotary switch. Clear as mud? -- Jeffrey Sharp