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IBM PS/2 Model 25 - Green Screen on Boot, No Post

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    IBM PS/2 Model 25 - Green Screen on Boot, No Post

    Hello all!

    Forgive me if this is already posted elsewhere, but Iím having trouble getting an old PS/2 Model 25 (8086) to boot up after digging it out of the closet. When I flip the power switch, the unit powers up (including power being fed to an add-on IDE hard disk attached to an expansion card that also feeds it power), but never actually posts, only displaying a dancing green screen. I took a look at the motherboard, reseated expansion cards and RAM, but donít see anything terribly out of order, at least by my uninformed eye. Any one have any thoughts, tips, suggestions, or resources I can check out?

    D29A9376-7722-4C93-8DFD-05DE4FC3178C.jpeg

    #2
    That's a tough one. If you had a vintage POST card ( http://minuszerodegrees.net/misc/post_cards.htm ) you could set it to port 90h and see if you're getting any codes at all from the BIOS. Past that, you'll need to hunker down with the hardware maintenance manual: ftp://ftp.oldskool.org/pub/drivers/I...e%20Manual.pdf
    Offering a bounty for:
    - A working Sanyo MBC-775 or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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      #3
      Thank you, Trixter! I donít have an illustrious POST card, (didnít realize they even existed!) but Iíll cozy up to the maintenance manual and hopefully report back with progress!

      Comment


        #4
        the monitor should NOT be green like that, all my 25's have a black screen (both b&W and color)

        It looks like a hardware failure either in the crt potion or in the video card. IBM is pretty good about having on-screen error codes, and if you solve the green crt issue, it might be telling you about the error as to why its not booting.
        It is a mistake to think you can solve any major problems just with potatoes.

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          #5
          Thank you, luckybob! That's sort of what I'm afraid of ... I feel like the CRT is beyond my abilities to remedy and I'm not optimistic about scouring for a replacement motherboard, though I suppose that might be the lesser of the two evils?

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            #6
            Alsoónot sure where the angry emoji is coming from, I appreciate everyone's feedback so apologies on that slipping in there!

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              #7
              As far as my own personal knowledge with fixing CRT screens, i'd classify my self in the category of 'knows enough to be dangerous".

              If I were in your position, i'd isolate the fault first. if you unplug the monitor from the motherboard and turn on the pc, does the image change? If the screen stays black, it would lead me to troubleshoot the monitor. If the screen remains green, I'd start to troubleshoot the crt.

              In addition, you can make your own 2x5 header -> vga cable adapter. one of the members here has done it, and made a video about the process. https://www.youtube.com/watch?v=KjnbSpuq90I I don't recall exactly which member he is here, but hopefully he will be kind enough to chime in. Worst case scenario, just search this site, it should come up.

              In most cases with the CRT, its bad caps that cause things to go all cactus. The fact the screen still comes up green, to me, is a good thing. It means the high voltage is working, and I'd wager the issue is in the "low" voltage side of the CRT. (if it is indeed the CRT).

              As for troubleshooting the motherboard (if it is the cause), check the easy stuff first. Is the power supply supplying the proper voltages? (while under load) re-seat all the parts you can, look for obvious broken parts.
              Last edited by luckybob; April 3, 2020, 03:09 PM. Reason: because proofreading is hard!
              It is a mistake to think you can solve any major problems just with potatoes.

              Comment


                #8
                Originally posted by luckybob View Post
                In addition, you can make your own 2x5 header -> vga cable adapter. one of the members here has done it, and made a video about the process. https://www.youtube.com/watch?v=KjnbSpuq90I I don't recall exactly which member he is here, but hopefully he will be kind enough to chime in. Worst case scenario, just search this site, it should come up.
                That would be me.

                My Model 25 has randomly started doing this actually itself, WITH a VGA card mind you (and grey because it's a black and white model). So far I've pointed at least my particular issue to the power good signal not going high, indicating some PSU issues. If you have a multimeter check the power connector for power good, that will be pin 1. If it's not that though, it could be a number of things and as mentioned a POST card would be needed since you're not getting any video output.
                IBM PS/2 Model 25, NEC V30 8MHz, 640KB RAM, ATI VGA Wonder XL, 2GB SSD, Ethernet, DR DOS 6/GeOS, Xircom PE3 Ethernet

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