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Thread: Whence Alpha among the hobbyists?

  1. #51
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    The PSU is made by ACBEL and model number is API0FS21 but, what a surprise, I can't find a drawing either.

    What I did discover is that the mains is on the small interconnect PCB and it don't half make your fingers tingle if you forget to turn it off at the plug.
    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 - AlphaServer DS10 - AlphaStation 225 - MicroVax II.

  2. #52
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    Quote Originally Posted by Gary C View Post
    A couple are showing a small sign of bulging.
    Bulging capacitors have failed. Replace the electrolytics.

  3. #53
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    Quote Originally Posted by cruff View Post
    Bulging capacitors have failed. Replace the electrolytics.
    I believe they are on the way, but its not always true they have 'failed'. Certainly the worst one (and its only slight) showed a reasonable value on the tester after I had removed it, but its possible if not likely that one of the others is dead. Give me something to do this afternoon when I have woken up after this night shift.

    They are going to be removed and tested, but I'm not spending too much on just changing components hoping to get lucky when I might have to replace the whole unit.

    Just wish I had a drawing, The components are too tightly packed to really be able to draw out the circuit, so I might end up replacing it with a modified ATX unit
    Last edited by Gary C; October 29th, 2020 at 07:11 PM.
    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 - AlphaServer DS10 - AlphaStation 225 - MicroVax II.

  4. #54
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    Quote Originally Posted by Gary C View Post
    I believe they are on the way, but its not always true they have 'failed'. Certainly the worst one (and its only slight) showed a reasonable value on the tester after I had removed it, but its possible if not likely that one of the others is dead. Give me something to do this afternoon when I have woken up after this night shift.

    They are going to be removed and tested, but I'm not spending too much on just changing components hoping to get lucky when I might have to replace the whole unit.

    Just wish I had a drawing, The components are too tightly packed to really be able to draw out the circuit, so I might end up replacing it with a modified ATX unit
    I find that you can't tell from the value, they seem to show the correct capacitance but not when you try and use them at high currents. Some even show a reasonable ESR but after replacement the last PSU I worked on was fine. The other thing that I have had to replace is the Opto Coupler.
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  5. #55
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    Quote Originally Posted by Chuck(G) View Post
    Please pardon a simple question from a non-DEC (at least since the 11/750 VAX) user, but why the enthusiasm for the PDP-11 and small VAXen, but nary a mutter about Alpha?

    Just curious is all.
    To return to the original topic, perhaps this is why:-

    https://www.ebay.co.uk/itm/293789928680
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  6. #56
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    I had my eye on that ebay item as well, I have one in my loft with Tru64 installed. Another project and not enough time

  7. #57
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    Miata MX5 motherboard??

  8. #58
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    Quote Originally Posted by g4ugm View Post
    To return to the original topic, perhaps this is why:-

    https://www.ebay.co.uk/itm/293789928680
    It was a pretty good deal at the starting bid of 99.99. Obviously, there are folks out there who still value them.

  9. #59
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    Quote Originally Posted by Chuck(G) View Post
    It was a pretty good deal at the starting bid of 99.99. Obviously, there are folks out there who still value them.
    Yes, but it soon went out of my price range.
    Dave
    G4UGM

    Looking for Analog Computers, Drum Plotters, and Graphics Terminals

  10. #60
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    Default Alphastation 255

    Just got my Alphastation 255 running and I am actually making this post using netscape
    Feels very unweildy, but I am impressed it even works at all

    Managed to repair the broken front panel clips too.

    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 - AlphaServer DS10 - AlphaStation 225 - MicroVax II.

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