daver2
10k Member
We used LSI-11 and PDP-11 machines to control and monitor power stations. Not too dissimilar from this system. We have more I/O points though...
Dave
Dave
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PDP-11 style front card
- Thread starter tech58761
- Start date
tech58761
Experienced Member
Sure enough. the board has 'Universal' on the back... thought it was maybe the board house or something.
Here I thought it was worthwhile, as I couldn't find any documentation on this board, but all I did was reinvent the wheel
Here I thought it was worthwhile, as I couldn't find any documentation on this board, but all I did was reinvent the wheel
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tech58761
Experienced Member
and here's the completed KiCad file
pbirkel@gmail.com
Veteran Member
Well, you learned a lot, right :->? I'm sure that we "out here" did. Suggest cross-checking your schematic with the print and associated BOM; I see at least one zener diode on the print. And "as designed" prints sometimes vary from "as built". We ought to calculate the RC constants in the various places and see how they compare to the Qbus power up/down specification.
tech58761
Experienced Member
Actually, I did a BOM compare and corrected some component values and also changed the part designators to agree with the print.
The one zener would be the 1N750, and that was on the input end of one of the comparator stages. I haven't done a detail comparison yet given how closely the components are drawn on Universal's schematic, but I am reasonably confident in the accuracy of the schematic I drew up, with the reverse engineering method I've worked out (and can describe in a separate thread if desired).
Well, there goes my confidence - the wiring matched as far as I could see, but I got a few part designators wrong. R3 / R17 swapped, LT1 / LT2 swapped, and functions on the toggle were swapped.
The one zener would be the 1N750, and that was on the input end of one of the comparator stages. I haven't done a detail comparison yet given how closely the components are drawn on Universal's schematic, but I am reasonably confident in the accuracy of the schematic I drew up, with the reverse engineering method I've worked out (and can describe in a separate thread if desired).
Well, there goes my confidence - the wiring matched as far as I could see, but I got a few part designators wrong. R3 / R17 swapped, LT1 / LT2 swapped, and functions on the toggle were swapped.
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tech58761
Experienced Member
Stepped back into the room with the PDPs and looked at the 'spare' chassis - sure enough, it's marked as an Universal Instruments 8222 controller and there's a small transformer right there on the backplane.
