Can you post a description of this box again? I had already deleted the earlier parts of the conversation. But it stuck in my mind. I hmay have the book on this box as I think it is the same as the couple I have. If so, there were two versions of the quad wide backplane. One is A-B-A-B all the way down. And one is A-B-A-B except for slots 6-7 which have C-D for use with the two board RL controller. Please post brand name and any model numbers yo have and I will dig thru my library. bill ________________________________________ From: cctalk [cctalk-bounces at classiccmp.org] on behalf of Noel Chiappa via cctalk [cctalk at classiccmp.org] Sent: Tuesday, April 4, 2017 6:35 PM To: cctalk at classiccmp.org Cc: jnc at mercury.lcs.mit.edu Subject: Re: KDJ11-B PDP 11/73 getting stuck in Exit standalone mode diag #56 So I seem to recall hearing tales of PMI cards emitting smoke when plugged into a Q/Q/ backplane. That doesn't seem to have happened here: So I wondered if his off-brand backplane didn't have +12V or -12V wired up - whatever it is that causes the damage. So I compared a list of PMI pins with a QBUS pinout, trying to see if it was the +12V or 12V that would be the problem. However, I don't see any PMI pins that conflict? (Well, some of them are ground, or +5V, but will that harm bus driver TTL?) Here's my list of PMI pins: CB1 PSSEL CD1 PUBMEM CE1 PBCYC CF1 PUBSYS CH1 PHBPAR CJ1 PSBFUL CK1 PLBPAR CM1 PRDSTB CP1 PBLKM CR1 PBSY CV1 PUBTMO DB1 PWTSTB DC1 PBYT DD1 PMAPE Anyone have any idea which pin(s) is the issue, when plugging a PMI card into a Q/Q slot? Noel