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Help Diagnosing Problems with an IBM 5150

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First post, by Tempest

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I'm having some issues with my IBM 5150 and I'm not sure where the issue might be. It's a late version with the final BIOS, 256K on the motherboard, it has a half height 5.25" and 3.5" drive in it (set to 720k), and it has a math co-processor chip. For cards I have an XT-IDE with an SD card adapter board, a gameport cart, a floppy controller card (IBM I think), a ATI EGA Wonder card (for use with my 5151), and a weird Six Pack clone by Multitech which has full memory to bring the system up to 640K (Picture below), but I'm not using the extra gameport or serial port add ons with it. The original 63W power supply that came with it originally worked, but it was making a whistling noise until it warmed up so I figured it was dying and replaced it with a beefier 150W power supply by Power Tronic. Everything seemed to be ok so I put it away for a year or two, but when I pulled it out of storage this weekend I started having issues.

I went to go and format the SD card using FDISK from DOS 5, which seemed to be working fine, when suddenly the monitor seemed to lose power. I turned everything off and tried again but this time when the computer had to reboot after making the partition the disk drive light stayed on when trying to boot the DOS disk and never actually completed the reboot (this would have been a warm boot). I decided to plug the monitor into its own power source (not into the onboard power supply) and tried again. I got a little further with FDISK when it crashed again but this time the monitor didn't lose power since it was on its own power source and I could see the screen was frozen while in the middle of trying to display something.

At this point I suspected that one of the cards might be bad or I might have bad memory somewhere. I yanked out all the boards except the video and disk drive board and booted into the BASIC. That ran fine for a good hour and never crashed so I booted a text adventure called Zyll (my options for programs are limited with 256K) and let that run for an hour. No problems there. I put in all the cards except the memory card and repeated the tests. Everything seemed ok with no crashing. My next step is try and put the memory card back in but I'm not sure what the dip switch settings should be since I can't find any info on the card. I'm hoping something is just misconfigured on it and maybe that's what's causing the problem. The only other thing I can think of is that the power supply is no good, but if that were the case you'd think it wouldn't boot at all. Even with the memory card in sometimes I can get it to boot an old HDD I have and everything seems to work ok in the brief tests I've done, so the problem is a bit intermittent.

Any ideas on what might be wrong?

http://atariprotos.com/temp/mystery.jpg

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Reply 1 of 9, by Tempest

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I plugged the memory card back in and so far so good. The SD card is formatting with DOS 5 which is further than I was getting before. Maybe one of the cards was loose? I find that hard to believe though since I had them screwed in. Or maybe this is just part of it intermittently working and it will start glitching again?

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Reply 2 of 9, by mkarcher

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Tempest wrote on 2022-05-29, 15:46:

Maybe one of the cards was loose? I find that hard to believe though since I had them screwed in.

It's unlikely that a card is loose when it is screwed in, but possibly some contacts were corroded and just removing and reseating the cards cleaned the corrosion due to the friction between the slot and the card.

Reply 3 of 9, by Tempest

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mkarcher wrote on 2022-05-29, 18:19:

It's unlikely that a card is loose when it is screwed in, but possibly some contacts were corroded and just removing and reseating the cards cleaned the corrosion due to the friction between the slot and the card.

Thats a good point. I should check the card contacts.

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Reply 4 of 9, by Tempest

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I did just get an error that said "Invalid COMMAND.COM Cannot load COMMAND, system halted". Any idea what that's about?

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Reply 6 of 9, by mkarcher

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Tempest wrote on 2022-05-29, 20:52:

I did just get an error that said "Invalid COMMAND.COM Cannot load COMMAND, system halted". Any idea what that's about?

Something is corrupted. This might be transient (i.e. it doesn't happen again after a reset), or the installation of DOS might be corrupted on the drive. If it is transient, you likely still have general stability problems. You could try running a RAM test (like the one in CheckIt) to test whether stability problems might be caused by RAM issues. The RAM on the mainboard is generally parity checked, so you be getting lots of "parity error" panic messages before you observe memory corruption. Most RAM expansion boards also used parity chips, so unless disabled by a jumper, I would expect parity error screens before you get random corruption if a memory chip is bad.

General contact problems at the ISA slot, or temperature-dependent broken solder joints thus might be more likely than RAM issues.

Reply 7 of 9, by Tempest

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It's a fresh dos install so I doubt it's corruption. A card with a bad solder joint or poor contact makes sense. I wonder if there's a way to tell which one it is?

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Reply 8 of 9, by Horun

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I suggest pulling the ISA Compact Flash Adapter card but leave all other cards installed. Boot to floppy and run it a while and use a few different floppy disks with minor games or apps and see what happens.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 9 of 9, by Tempest

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Horun wrote on 2022-05-30, 04:22:

I suggest pulling the ISA Compact Flash Adapter card but leave all other cards installed. Boot to floppy and run it a while and use a few different floppy disks with minor games or apps and see what happens.

I can try that. That card is the newest one.

I played Secret of Monkey Island on it for a good half hour this morning (meaning it barely got through the first scene, the poor 5150 isn't made for that), and it seemed stable. So far so good.

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For when excellence and burnished fineries need to gently visit the warmth of your tablery

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