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Thread: PDP11/05 - Quick look and Teardown

  1. #11

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    Thanks for posting the video.

    You have an interesting combination of memory boards in your system. I'm pretty sure the Plessey board is a stand-alone Unibus memory, meaning it has all the necessary addressing / driver circuits to operate the core, and thus doesn't require the G110 and G231 boards to function. I purchased one of these off ebay after I got my /05 (which came with an H216), but unfortunately the core in it was busted. Perhaps at one point your system had an H214/H215/H216 that died and was replaced by the Plessy.

    Also, definitely no sign of those extra console connector wires in my system. I'm intrigued as to what they were trying to accomplish there.

    --Jay

  2. #12
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    Quote Originally Posted by Dare View Post
    I'm pretty sure the Plessey board is a stand-alone Unibus memory, meaning it has all the necessary addressing / driver circuits to operate the core, and thus doesn't require the G110 and G231 boards to function.

    Perhaps at one point your system had an H214/H215/H216 that died and was replaced by the Plessy.

    Also, definitely no sign of those extra console connector wires in my system. I'm intrigued as to what they were trying to accomplish there.
    Thanks, that's interesting.

    I knew of the G110/H214/G231 combo, and wondered if that Plessey module was supposed to replace an H214, why did it have a whole lot of extra electronics that the H214 doesn't? And which looks a lot like the electronics on the G110/G231. So your suspicion that the Plessey board can run standalone seems plausible.

    I do have at least one H214 around here somewhere (but it has a broken chip), so maybe it was all meant to be in there, for more memory.
    Or as you surmise, maybe it just replaces the broken H214.
    But then, there was an undamaged H214 also, so maybe not, but I gave it away long ago.

    I also have another (different) Plessey module that seems to have been in a 4 slot Unibus extension.

    It's also good to know that I can probably forget about those extraneous wires, and the UART TBMT bodge wire.

  3. #13

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    Nice machine!

    I have also a Galway PDP11 in the small cabinet. But mine is called the PDP11/10.
    It seems they have changed the cooling system over time. You have a ventilation grille
    underneath the switches. My machine is closed an the front. In my machine the air is
    pulled into the machine at the boards side and is blown out at the power supply side.

    So the heat of the boards is actually blown over the power supply. Not the best solution I think...

    Is the airflow of both of your fans in the same direction like from the back to the front?
    Or did they keep the airflow direction the same as my machine?

    PDP11_10 01.jpg air flow.jpg

    Regards, Roland
    WTB: Case for Altair 8800 ...... Rolands Github projects

  4. #14
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    Quote Originally Posted by Roland Huisman View Post
    Nice machine!
    ... But mine is called the PDP11/10....
    Is the airflow of both of your fans in the same direction like from the back to the front?
    Thanks, I'm not sure what the difference is, but the manuals seem to lump the 11/05 & 11/10 together...

    I haven't powered on my 11/05 recently (if ever?), and it's all in pieces anyway, pending new power supply caps.
    Looking at the fans, I can't see an airflow direction arrow, but both of them have the stator/label side of the motor toward the outside.
    So if say, the air comes in from the stator side (needs to be checked), they would be blowing onto the boards, and into the PSU.
    HTH

  5. #15
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    Quote Originally Posted by Roland Huisman View Post

    So the heat of the boards is actually blown over the power supply. Not the best solution I think...

    Regards, Roland
    Much better than the heat from the PSU being blown over the boards !
    Current fleet
    TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - VAX 3100,3300,4000VLC & 4000 Model 96 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - DEC Micro PDP 11/73 - IBM 5160 XT - Multibus 286/10 - Alpha server - MicroVax II.

  6. #16

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    Quote Originally Posted by Gary C View Post
    Much better than the heat from the PSU being blown over the boards !
    Agreed!
    WTB: Case for Altair 8800 ...... Rolands Github projects

  7. #17
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    It's just my observation but the solid cast metal fascia grille seemed to be only on the early 11/05 and 11/10, from late 1972 to early 1973.
    This can be seen in the PDP-11/05/10/35/40 processor handbook photos on pages 4-74 and 6-24.
    My s/n 151 machine has this style solid grille. It also has the cast-in pure white digital logo on the console frame, which along with the change to the plastic slotted grille went to the separate stuck-on magenta badge for the majority of 11/05 production.
    Roland's machine shows both the early grille and the common badge style. I did some waterside decals for this badge a while ago.

  8. #18
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    Just correcting myself above, I really meant from 1972 to 1973 for the early grille and bezel, from the machines I've seen on eBay and elsewhere. Also the early bezel was painted black just on the strip directly underneath the switch paddles,as well as having the cast-in nameplate.

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