Paul Anderson wrote: That's the problem. ?What he needs _isn't_ a generic Unibus backplane (technically an SPC backplane), but rather an LP20 backplane. ?The LP20 backplane has Unibus in and out, but is wired specifically for the LP20. This is the same situation as for backplanes for many Unibus devices such as the MM11-E, RH11, and VT11; they pass Unibus through but are very specialized backplanes that aren't useful for anything else.

Paul Anderson wrote: > I'm familiar with the various DEC Unibus backplanes, but I'm not a LCG > guy. I just wondered it it was in the 11/40 front end. Either way, > with a part numder I might find something on fishe.

The LP20 backplane is DEC p/n 54-11704. The complete backplane assembly is 70-11590. The complete LP20 wired assembly is 70-11427. IIRC, Rich included those part numbers in his original request. The LP20 does go into an 11/40, but only in a KL10 system. The backplane doesn't have a model number (e.g., DD11-somthing), since it is only a part of the LP20 and not used for anything else.

Actually, the LP20 can also be used in the Unibus on a KS-10 system. Unfortunately for us, none of our KSes have an LP20.

We have been trying to get working an LP20 printer interface on our 2065. ?We discovered just today that the issue we have had with bad control signals was not due to bad boards, but rather was due to the fact that the bottom 4 segments of the Unibus backplane into which the control card plugs have no (0) wires wrapped around the pins. We have the LP20 schematics, but the wiring diagram *for the backplane* is not included. ?It also is not to be found on microfiche, although there is a reference to it, with document numbers. ?We are specifically looking for 70-11427, 54-11704, and 50-11703. If anyone has any of these documents, please let us know ASAP. ? Otherwise, a young EE is going to have to spend time with the complete set of LP20 schematics and a spreadsheet program to generate a wire list and re-wire this thing by guess and by $DEITY, a process that will take several weeks with no guarantee of correctness of result. Thanks, Rich Rich Alderson Vintage Computing Sr. Systems Engineer Vulcan, Inc. 505 5th Avenue S, Suite 900 Seattle, WA 98104 mailto:RichA at vulcan.com mailto:RichA at LivingComputerMuseum.org http://www.LivingComputerMuseum.org/

I am almost certain that neither of my KS10s have an LP20 installed, but I will check tomorrow just to be certain. If I have one, I'll either document it or loan it to you folks. -Dave

On 03/16/2012 06:47 AM, Sander Reiche wrote: :-) Feel free to come visit!