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8KW Plessey core UNIBUS board PM 1105 - Looking for Maintenance manual and/or Engineering drawings

WolfgangSchmitz

New Member
Joined
Sep 15, 2016
Messages
8
Hi all,
long time reader, first timer poster.
I'm restoring a small PDP11/05, that came with a G110, G231 and H214 combination supplying the lower 8KW of memory
and a second board of 8KW fitting in an SPC slot, type Plessey PM 1105.
This board shows different errors in memory tests.
So I would be very grateful, if somebody could help me with documentation about Plessey PM 1105.

Thanks,
Wolfgang
 
I have documentation of the PM 1116 and I wonder how that compares to your board. I'm not sure if this documentation is online already... Let me know... Do you have pictures of your board?

Regards, Roland
 
Hello Roland,
nice to read you!
If tried to find the documentation about PM 1116 on the web, but no success.
It would certainly be helpful to to have your documentation, although it may not be the same layout as of my PM1105.
But I would probabely have more insight of the basic idea that Plessey followed.
I send an image of my board.
So far, I could deposit to and examine from the memory using Joerg Hoppe's UNIBONE together with PDP11GUI.
Looks like Address errors, so I'm following the address lines.
They go to SP380A NOR-Gates, with one leg grounded, as inverting buffers, then to SN74174 D-FlipFlops and then to SN74145 1-of-10-Decoders.
Trying to find irregular behaviour in this chain, but that takes time...

As said, I would appreciate very much, if I could take a look at PM1116.

Best wishes
Wolfgang

1.jpg
 
I have documentation of the PM 1116 and I wonder how that compares to your board. I'm not sure if this documentation is online already... Let me know... Do you have pictures of your board?

Regards, Roland
Hello Roland,
Hello 1944GPW,
meanwhile I found a sticking bit at address A06, one of the SN74174 D-FlipFlops.
But there are more defects on the board, which are not easily associated to the address bus.
I tried to answer the post of FoothillsGeek, as you proposed, but I believe, that I could not get through to him.
So maybe your PM1116 and/or PM1100 documentation could help a bit to get more clarity?
I can find neither of them online, so maybe you could help me out?


Thank you
and have a nice weekend
 
Last edited:
Hope this helps!
Thank you very much!
From the block diagram(s) I can now understand, why the outputs of decoders are wired ored and how the basic
addressing, reading and writing is accomplished.
I will take my time to dig into that. And well, yes, the numbering of the ICs is completely different compared to my board,
but basically, it looks like Plessey used the same structure.
So, thanks again, and have a nice sunday!
Wolfgang
 
I have documentation of the PM 1116 and I wonder how that compares to your board. I'm not sure if this documentation is online already... Let me know... Do you have pictures of your board?

Regards, Roland
Roland,
I have a Plessey PM1116B 16KW x 16 core memory board and I would love to get a copy of the manual for it.

Also, I have a DataRam DR-114M 32KW x 18 core memory board that I am also looking for a manual or other documentation.

Thanks,
Mark
 
This is to my moderators:

I think that I have found the defects on my Plessey memory board.
To my eyes, they are rather interesting, so that I'm thinking about sharing what I have learned while searching.
Is it a good idea to write some sort of article and give this info to the public as a contribution?

Regards, Wolfgang
 
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