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Diagnosing a non-booting 5150

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    Diagnosing a non-booting 5150

    I bought a 5150 off ebay last week, I think I got it for a reasonably good deal. It was in "powers-up" condition, which in eBay-speak often doesn't mean a whole lot. That's fine, as I'm always looking for a project. When powered on the first time, there's no visible or audible indication of anything happening, other than the fan spinning at what seems to be a normal fan speed. I haven't checked PSU voltages yet, i'm going to check PSU voltages today after work.

    I pulled the installed video card and installed a known-working-in-8bit VGA card. A few more attempts didn't boot, but finally I did get a boot that had one long beep and two short beeps followed by the VGA BIOS displayed on screen. I was able to reproduce that a few times. The beeps were likely due to SW1 being configured for MDA while I had installed a VGA adapter. However, after correcting the switches (and putting them back to the way they were several times), I haven't been able to reproduce this success. No beeps. No VGA output.

    My plan is to follow the diagnostics at minuszerodegrees.net, but I had a few questions.

    First, the video card this thing came with says "Video-7 1985" on the back. It has a MC6845P. There's a single 9-pin female din. No composite connector. It has an onboard 2732. Can someone confirm whether this is a MDA adapter, or something else? ETA: FCC ID is D2A62LMGA, leading me to believe it is monochrome.

    Second, I've ordered an adapter so I can burn a 26xx diagnostic ROM and put it on the motherboard in place of the BIOS. My understanding is these diagnostic ROMs work with MDA, CGA, and sometimes EGA, but definitely not VGA. That means if I want to go that route I'm going to have to find some way to convert MDA or CGA into something I can view on a modern LCD. I got rid of my last multisync monitor a decade or two ago. Any suggestions on the best way to do this? Should I just buy on eBay a CGA card that has composite output?

    Thanks,
    Scott
    Last edited by smbaker; March 16, 2018, 08:32 AM.

    #2
    Originally posted by smbaker View Post
    First, the video card this thing came with says "Video-7 1985" on the back. It has a MC6845P. There's a single 9-pin female din. No composite connector. It has an onboard 2732. Can someone confirm whether this is a MDA adapter, or something else? ETA: FCC ID is D2A62LMGA, leading me to believe it is monochrome.
    Could you post a photo?

    Given Video 7's products, I would think enhanced CGA or EGA, or even combo MDA switchable. Sounds like an interesting card.

    Originally posted by smbaker View Post
    Second, I've ordered an adapter so I can burn a 26xx diagnostic ROM and put it on the motherboard in place of the BIOS. My understanding is these diagnostic ROMs work with MDA, CGA, and sometimes EGA, but definitely not VGA. That means if I want to go that route I'm going to have to find some way to convert MDA or CGA into something I can view on a modern LCD. I got rid of my last multisync monitor a decade or two ago. Any suggestions on the best way to do this? Should I just buy on eBay a CGA card that has composite output?
    Video connection wise, composite CGA would be the least complicated. Keep in mind that later clone CGA cards (especially the small Taiwanese ones with everything in one chip) will usually output composite on one of the RGB port pins even if they don't have an RCA port.

    I don't have real experience with these diagnostics chips, but wouldn't a VGA card in "Pure CGA" emulation work? I guess that would depend if the VGA card still needed to initialize things through its BIOS, which the diagnostic roms wont do. If it did work, then a normal VGA monitor could be used.

    Edit: after thinking about it for a few minutes, now I remember trying a trick like that on a machine with a BIOS that didn't support VGA, and that trick didn't work. So probably wouldn't work here.
    Last edited by SomeGuy; March 16, 2018, 09:30 AM.

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      #3
      Here's a picture of the Video-7 card.

      video7mga.jpg

      After playing with the PC a bit during lunch, I found that the VGA card works sporadically, almost to the point of not working at all, in slot 2 on the motherboard. This is the same slot the Video-7 card came out of. Most of the time the PC won't boot. Rarely it will give the "no video card" installed beep. Even more rarely it'll actually boot up. The card works fine in any other slot on the motherboard.

      I'm not sure if this suggests a problem with the edge card connector itself, or a problem with the soldering between the edge card connector and the motherboard. I haven't taken the motherboard out to look at the underside yet.

      I also ordered myself one of these: https://www.ebay.com/itm/Brand-New-A...72.m2749.l2649, on the assumption it would be nice to have a way to display MDA and CGA on my LCD. As I understand, while this thing says it converts "CGA" and "EGA", it's talking analog signals, not digital, and I'll need an external DAC. A DAC for monochrome doesn't sound that difficult.

      Scott

      Comment


        #4
        Originally posted by smbaker View Post
        I also ordered myself one of these: https://www.ebay.com/itm/Brand-New-A...72.m2749.l2649, on the assumption it would be nice to have a way to display MDA and CGA on my LCD. As I understand, while this thing says it converts "CGA" and "EGA", it's talking analog signals, not digital, and I'll need an external DAC. A DAC for monochrome doesn't sound that difficult.
        FYI. Member Retro Canada recently designed a complete 'MDA/EGA/CGA to VGA Converter' (MCE2VGA). See [here].

        Comment


          #5
          Originally posted by smbaker View Post
          I also ordered myself one of these: https://www.ebay.com/itm/Brand-New-A...72.m2749.l2649, on the assumption it would be nice to have a way to display MDA and CGA on my LCD. As I understand, while this thing says it converts "CGA" and "EGA", it's talking analog signals, not digital, and I'll need an external DAC. A DAC for monochrome doesn't sound that difficult.
          See the Retro Canada project mentioned previously. Also, I've had good success with a gglabs CGA2RGB TTL-to-analog converter connected to the gonbes you ordered.
          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)

          Comment


            #6
            Originally posted by modem7 View Post
            FYI. Member Retro Canada recently designed a complete 'MDA/EGA/CGA to VGA Converter' (MCE2VGA). See [here].
            Shameless thread hijack here!! I still have some of Retro Canada's MCE2VGA converters for sale. Fully assembled and tested. Send me a PM if interested!!

            OK, you can have your thread back now

            Comment


              #7
              Originally posted by modem7 View Post
              FYI. Member Retro Canada recently designed a complete 'MDA/EGA/CGA to VGA Converter' (MCE2VGA). See [here].

              Thanks! I can see more boards being added to my next pcb order...

              Comment


                #8
                Still having some fun with my new old 5150... I've noticed that I can't get it to boot from XT-CF-Lite or from a DiskOnChip. In the XT-CF-Lite case, it says it's booting "C", pauses a second then goes off an boots "A". With either of these, if I do boot from the floppy the drive letter is there, C:, but I get an error when trying to access it.

                Is it the case that the 5150 BIOS doesn't support hard drives?

                Comment


                  #9
                  If it didn't support hard drives, then you would not see it attempting to boot from C at all. It sounds more like the CD card is not partitioned and formatted properly.

                  Boot from a floppy and go through the steps of running FDISK, creating/recreating any partition, and formatting.

                  Comment


                    #10
                    Originally posted by SomeGuy View Post
                    If it didn't support hard drives, then you would not see it attempting to boot from C at all. It sounds more like the CD card is not partitioned and formatted properly.
                    The CF card and the DiskOnChip both boot fine in another machine. I will point fdisk at it and see what it thinks is there.

                    Comment


                      #11
                      Mystery solved. The dip switches on the motherboard were configured for three floppies.

                      Life makes more sense now.

                      Comment


                        #12
                        Originally posted by smbaker View Post
                        Mystery solved. The dip switches on the motherboard were configured for three floppies.
                        Life makes more sense now.
                        I have that issue listed at [here] for the VCF's XT-IDE.
                        Yet to experiment with DOS version.

                        Comment


                          #13
                          Originally posted by modem7 View Post
                          ......Yet to experiment with DOS version.
                          I just changed the dip switch settings from 2 floppy drives to 3 then 4 floppy drives on my IBM 5160 with 1/10/86 bios, Original Rev 1 XTIDE Card with XUB R591 running DOS 6.22, On both occasions i get as expected a 601 error and pres F1 to continue, I press F1 and it continues to boot successfully from the CF.

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