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Thread: XT style power supply?

  1. #1
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    Default XT style power supply?

    Hello all!

    I have a 486 motherboard that I'd like to get running again.

    I have a few ISA plug in cards that may still work with it, but I have no case or power supply for it

    I'd guess that the most important step (assuming I can find a video display adapter card) is to connect
    a power supply and see if the BIOS is still alive in EPROM.

    Would anyone have a line on an XT type power supply? I believe that the supply had two power
    connectors that ran to the motherboard.

    I'm at

    bignick@execpc.com

    or on this forum.

    Thank you,
    --KC9KEP

  2. #2

    Default

    You want an AT psu. I bought the new Startech 230 watt psu and it works great. That might be overkill for you but it's the only decent new AT psu.

  3. #3
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    For testing I suggest you use one of these adapters with an ATX supply.

    https://www.ebay.com.au/itm/20P-ATX-...sAAOSwjIVafRQk

    It will be less costly if the board turns out to be faulty. Once you know the board works then you should look for an AT style case. Most later AT style cases use a power supply with the same form factor as the common ATX power supplies, so the adapter may come in handy even if the board proves to be a good one.

  4. #4

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    Well, I have a Baby-AT PSU but it needs a SPDT power switch (it has spade terminals and a schematic for where to connect them on top). Currently I have it on an e-bay auction but if it keeps failing to sell I'd be willing to pull it and ship it out. I don't need it because all my machines are full XT/AT form factor.

  5. #5
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    Default

    Here, buy a brand new AT power supply that will work very well for a 486. Link only $26 and available with Prime shipping.

    IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
    IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
    Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

  6. #6

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    Quote Originally Posted by lutiana View Post
    Here, buy a brand new AT power supply that will work very well for a 486. Link only $26 and available with Prime shipping.
    Isn't thaT A ps/2 psu?
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  7. #7
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    Quote Originally Posted by Stone View Post
    Isn't thaT A ps/2 psu?
    No, I bought one and it's an AT power supply. No idea why they list it as a "PS/2 Power supply".

    IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
    IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
    Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

  8. #8

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    Quote Originally Posted by Stone View Post
    Isn't thaT A ps/2 psu?
    That's the one I mentioned.

  9. #9
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    Austin, Texas
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    Quote Originally Posted by David_M View Post
    For testing I suggest you use one of these adapters with an ATX supply.

    https://www.ebay.com.au/itm/20P-ATX-...sAAOSwjIVafRQk

    It will be less costly if the board turns out to be faulty. Once you know the board works then you should look for an AT style case. Most later AT style cases use a power supply with the same form factor as the common ATX power supplies, so the adapter may come in handy even if the board proves to be a good one.
    These won't work unless you have an ATX supply with a -5v rail. Many motherboards back then refuse to even power on if the -5v rail is missing.

    The -5v rail was removed from the ATX spec back in 2003 so you're going to need a very old PSU to get it.

  10. #10
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    Quote Originally Posted by GiGaBiTe View Post
    These won't work unless you have an ATX supply with a -5v rail. Many motherboards back then refuse to even power on if the -5v rail is missing.

    The -5v rail was removed from the ATX spec back in 2003 so you're going to need a very old PSU to get it.
    Firstly early ATX supplies do have -5V, it was removed with version 2.0 of the specification but optional from 1.2 onwards.

    486 motherboards dont use -5v so they will power up with no problem on the adapters. The only thing I can think of that required -5v was 4116 DRAM chips. The last IBM board to use 4116 RAMS was the original PC, so even an XT will boot without -5v
    Last edited by David_M; April 22nd, 2018 at 05:59 PM.

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