486 VLB upgrade to MicroLab Case
I was unsuccessful with the MicroLab 286 motherboard. But I tested putting this 486 VLB motherboard in the MicroLab case and it will fit. So, I am going to put this 486 in the MicroLab case.
I got this 486 at PT Surplus. It came in a full tower, 25” high. I don’t need such a big case so I am going to clean it up and put it in the smaller MicroLab desktop case. This motherboard is a VLB type and has five ISA slots and three VLB slots. It came with several cards, but no sound card. The cards are a CD-ROM interface, Modem, I/O card, Floppy and Hard Drive controller (VLB) and a video card (VLB). There are two IDE hard drives, one CD-ROM, a 3.5” floppy drive and a 5.25” floppy drive.
I removed the motherboard from the case. It is a little dirty but there is not any corrosion. It uses a CR2032 battery. The CPU heat sink and fan are the dirtiest. There are two SIMMS installed and there are two slots open (total of four slots). The keyboard is a 5-pin DIN type.
I will take the power supply out and clean it up and use it in the new case. The old MicroLab power supply still works and can be stored for future use. [I may use the MicroLab power supply. They look very much the same but I think the one in the MicroLab case may be better. It is 200 Watts. I did end up using the MicroLab supply. The power supply that came in the large tower case is not working]. The MicroLab case has three external 5.25” bays and one 3.5” external bay. There is room for another hard drive under the power supply. But I think I will stay with one floppy, one hard drive, and one CD-ROM. [I ended up using both floppy drives].
I tried powering on with the MicroLab power supply and I got mixed results. Once or twice I did get a front power LED and the small fan on the CPU heatsink “bumped” and stalled. I got no screen readout. I decided to try the original power supply that came in the huge tower. That gave me nothing. I then tried the power supply from the VIP 200 286. It worked! The screen came on and the memory counted down but then I got an error saying the keyboard was missing.
I thought the power supply from the MicroLab 286 was working but now I am not sure. I am going to try it again just to confirm if it does the same thing. I was able to figure out why the keyboard was not working (in line fuse on MB) and I temporarily bypassed the fuse with a jumper wire. I also took out the disk controller card before I booted. I want to try the MicroLab power supply with this configuration before I label it bad.
I swapped in the MicroLab power supply and it worked. It may have been disabled by the bad keyboard fuse. Or maybe it was not firmly connected at the wire connectors. At any rate it seems like the MicroLab power supply will work.
Now I need to solder in a fuse for the keyboard on the motherboard. In the meantime I will put in the other cards and drives and see what else is working or not working with this machine.
I put in the drive controller card (VLB Card) and hooked up the 3.5” floppy and the two IDE drives that were in the case. One of the hard drives could not be detected and had a knocking sound. I unplugged it and only had the one HD attached. I can detect a drive in the BIOS and set it to a 520MB drive. But on boot I get a Hard Drive failure and then I hit F1. After hitting F1 I get a boot of MS-DOS 6.22 and it asks for the date and time. The date and time are correct and just hit enter on both. This brings me to a C:\> prompt. When I put in the DIR command all I get is the command.com. VER reports MS-DOS 6.22.
So, apparently the hard drive has a MS-DOS 6.22 boot but there is nothing else. There are no DOS or Windows files. (The Windows files are probably on the other drive that is not working?)
Why do I get a message saying HD failure but still get a boot to DOS off of the same drive? (See below, I had the wrong drive parameters).
The BIOS shows ram as 32Mb and CPU Type DX4-S at 100Mhz. Two serial ports and one parallel port.
I changed the BIOS to boot first from A: After reboot I got the hard drive fail error (20) and then hit F1. The floppy tries to read the boot disk but it does not read. The floppy drive light is on and the cursor is blinking on screen. But it is not booting. The floppy drive does not sound good. It seems to be spinning but not reading. Maybe try the cleaning diskette? I was able to get a directory when booted in MS-DOS 6.22 and I ran Checkit from this floppy drive. So it is at least working a little. Just not booting.
I connected the 5.25” drive as the B: drive. I was able to read several 1.2M diskettes, and the IBM PC-DOS 3.3 diskette, which I think is a 360k diskette. Then I reset the A: drive to 3.5” 720k and set the boot to “A, C” and rebooted. I got the usual hard disk fail (20) message and this time I got the Floppy disk fail (40) message. I put in a DOS 5.0 boot disk formatted as 720k. Then I hit F1. It failed to recognize the disk and asked to supply another disk. I put in the 1.44M DOS 5.0 boot disk and hit enter. The computer booted from the MS-DOS 6.22 on the hard drive.
Now I will try to use the 5.25” floppy to boot, as A:. Reset BIOS to A: as 1.2 and B: as none. Put in a DOS 5.0 boot disk in the 1.2M drive A: and reboot. Hard disk fail (20) but no other error. Hit F1. This time the computer booted from the floppy.
Both floppy drives seem to work but I can’t boot off the 3.5”. I can boot off the 5.25”.
Maybe there is a setting on the disk controller card?
(I did notice that the floppy disk loaded faster after I correctly set the hard drive and no longer got the hard disk failure error. Maybe the floppies will work better now?)
And when I used FDISK from the DOS 5.0 boot the program seems to look for a second drive, even though it is not present in the BIOS. The partition table? [I had the second hard drive entered as “user” but no parameters. When I set it to “None” it no longer looked for second drive].
Maybe try another hard drive and format with DOS 5.0? Not sure yet if I want to destroy these two drives that came in the case yet.
Anyway, I do seem to have a working computer here. I need to solder a wire for the fuse bypass, or get another fuse. Then I can put it back in the MicroLab case with one or two floppy drive(s), one hard drive, and one CD-ROM. There is no sound card so will have to use the CD-ROM audio only. Also will need a serial mouse.
I ended up soldering in a jumper wire over the fuse for the keyboard. I just need to remember to not unplug or plug in a keyboard with the power on.
I reassembled the motherboard in the case, power supply, VLB video card, VLB Multi i/o and Drive Controller, and the ISA CD-ROM controller. I also attached the wires for the front panel. I power it on and the fans came on and the keyboard lit up but there was no video. I turned it off and removed the ISA CD-ROM card and powered on again. Same thing. I unplugged the front panel wires then rebooted. That worked. I now got the video screen with the familiar hard disk failure (80).
I tried another hard drive, the one from the NEC 286. It also failed and could not be found with FDISK. I removed the original hard drive and looked up the specs on the Internet. It turns out I had the drive parameters wrong. I used the parameters I found for the drive and rebooted. This time I did not get the hard drive fail error and it booted with MS-DOS 6.22. I rebooted from floppy to DOS 5.0 and then ran FDISK and deleted the partitions and created a new partition. I got a warning from the BIOS but after I confirmed I was able to finish the partition and reboot. After reboot I checked the disk with FDISK again and it looked good this time.
I ran a format on the C: drive. It is running now and there are several recovery messages but it is moving forward, slowly. The message is “Trying to recover allocation unit nnnnn.” Apparently this drive had crashed and there are several sectors needing attention. Hopefully it will finish formatting and then I will install DOS 5.0 onto the hard drive.
The format finished. I reset the 3.5” 1.44M drive as the A: drive and rebooted with the MS-DOS 5.0 diskette. It booted and I installed DOS 5.0 to the hard drive. I rechecked the BIOS and set the floppy drives to A:=1.44M/3.5” and B:=1.2M/5.25” and set to boot A,C. Rebooted and tested all drives. Everything is working. The floppy drives are booting now. Apparently the hard drive settings were affecting the floppy boot. Now that it is correct it is all working. I started Checkit and am running a test on the Hard drive.
Next will be to install Windows and a Mouse and the CD-ROM driver. Finally, I need to clean up the faces of the drives. Then I can re-assemble the case enclosure and this machine will be done.
This will be my fourth 486 in my collection - and the highest specs for the processor itself. This is now my “MicroLab 486”, taking the place of the former MicroLab 286.
I wonder if this case will be a problem for the 486DX4-100 and heat. The original tower case had a lot more room. Plus the fan on the heatsink seems to not spin sometimes. I may have to add a cooling fan, or try another case. Let’s see how this goes.