Help needed: Two problems with my new Turbo XT

Posted by SenorPeterz@reddit | vintagecomputing | View on Reddit | 3 comments

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SenorPeterz@reddit (OP)

Yesterday, I got my hands on an old IBM-compatible Turbo XT (Copam PC-401 Turbo) via Facebook Marketplace for $60.

The seller’s dad had it as his work computer in the 1980s, and the seller stated that it had not been used for 35 years or so. From what little information I could glean online before the purchase, it seemed like it would have an I/O card with an RTC on it, meaning a battery, meaning a very, very high probability for a battery leak (perhaps just on the card, but likely also on the motherboard itself).

Judge by my surprise when, after getting the computer home and opening the box, everything looked excellent. The I/O card did indeed have a battery on it, but no signs of any leakage anywhere. Wonderful!

Contents

This is the motherboard.

The computer contained the following ISA cards:

· The abovementioned I/O-and-RTC card

· A combined MDA/CGA graphics card (“Intelligent” something)

· An MFM hard drive controller

· A floppy disk controller (with 34 pin connector at the card, but edge connectors on the rest of the cable)

It had the following drives:

· A 20 mb MFM hard drive, which seemed to work perfectly fine. Found some old games on it that I ran without any issues.

· Two 360k 5 ¼” floppy drives, both of which worked fine.

Saving the files for posterity

I promised the seller to get as much of the hard drive content as I could off the drive and send it to him. For this reason, I slotted in my XT CF Lite 4.1, which I have used with great success in my 5160/XT system, with a 32 mb compact flash card in it.

As suggested here, this did work reasonably well, even with the MFM still hooked up:

· If I just booted the system up normally without interfering, I could see the XUB lines during bootup (with the option of booting from A or C, etc), and it would start up the DOS 2.1 on the MFM just as fine as it did without the XT-CF-Lite. However, when doing so, I was unable to access the CF card (D:). “No such drive”. Running fdisk, I could see that there was another drive in the system – I was just unable to access it.

· When I disconnected the A: 360k drive and installed a 3.5” floppy drive in its place, and then booting up from A: with a PC DOS 5.02 floppy (the first of three 3.5” install diskettes) inserted, I could access the CF card on D: just fine – run games on it, copy files to and from floppy et cetera, but C: (MFM) wouldn’t work properly - when trying to access the MFM drive on C: and running dir, I would get first some weird ASCII characters and then just see three files listed. IE, no easy way of moving files from MFM to CF. Oh well.

· Pressing the Turbo button to switch it to red (to go from 4.77 mhz to 8 mhz) didn’t work. The LED would stay green. However, running the file PCSPEED (found on the hard drive and mentioned in the included instruction booklets that I got with the purchase), the LED would switch to red and the appropriate increases in performance could be noted in games, as well as in benchmark tests in CKPRO and Norton SYSINFO.

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SenorPeterz@reddit (OP)

My problems and the questions I have for this community

1: The keyboard situation

My initial plan was to move the motherboard to an unused 5160/XT case that I have left over, maybe together with the Turbo system’s PSU.

· The main problem here is evident when looking at the two pictures included in this post: The Copam PC-401 Turbo has the keyboard connector on the front of the case, instead of the back of the case like the original 5160 motherboard and most clone XT/AT boards.

· The motherboard still has the traces for the keyboard connector at the usual place in the back, but without the actual connector. I guess I could desolder a connector from a non-working board and solder it in place on this one, but I have neither the know-how, nor any soldering equipment, so that is not an option.

· The keyboard is connected to the Turbo motherboard on some pins near the front of the case, as indicated on picture 2, with a black cable running from the connector to the mobo.

· One conceivable solution would be to get a longer cable like that, and somehow loosen the keyboard connector from front of the case and move it to the back, with the internal cable running across the motherboard, but I have no idea if such cables are even available, or if this was some sort of proprietary solution specific to this motherboard.

· I’ve tried googling for like “XT internal keyboard cable” and such, but got no relevant hits.

Question: Does anyone know what this cable (as seen on picture 2) is called and/or does anyone here have another viable solution for how to be able to use this motherboard in my 5160/XT case?

2: The floppy situation

Leaving the keyboard issue, and thus the case-moving plans, aside for the moment, I instead chose to migrate some cards and stuff from my XT to the Copam Turbo motherboard:

· I removed the Hard drive controller and tried removing the actual MFM, but even though I unscrewed the screws on the left plate on the tray, the hard drive unit seems to be fastened to the right side somehow (not with screws though, as far as I can tell) so I couldn’t get it loose. Thus, I kept the MFM in place (albeit unconnected) at the bottom half of the left hand tray. With this solution, the system would now use the CF card in the XT-CF-Lite 4.1 as C:.

· I switched out the combined MDA/CGA video card and placed my EGA Wonder 700+ card in its place, making the appropriate DIP switch adjustments as indicated by the manual.

· Starting the computer, XUB would boot and the CF card would work flawlessly as C:. However, I noticed that I couldn’t get my 3.5” floppy to work anymore (though, nota bene, it worked without issues earlier. B: would work, and I could move files to and from a 5¼” disk in that drive, but A: wouldn’t.

· The LED on the FDD would turn on momentarily when trying to access the floppy disk within, but then silence and error message.

· When during XUB boot-up I tried to boot from A:, with a DOS disk in the drive, the FDD LED would once again turn on momentarily, but then it would go silent, I would get an “error 2h” message and XUB would boot DOS from C:.

Troubleshooting this, I did the following:

· Tried three different floppy disk controllers, without success.

· Tried three different floppy cables, without success.

· Disconnected the remaining 5¼” drive (with the appropriate DIP switch adjustments on the motherboard to indicate single floppy drive) to use only the 3.5” one, without success.

Again, the 3.5” drive worked fine when I used it initially on this computer, but now, no matter what I do, I cannot get it to work.

Question: What might be the problem with getting the 3.5” drive to work, and what can I do to solve it?

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SenorPeterz@reddit (OP)

I have figured out the floppy issue!

• When reconnecting the hdc and the mfm drive, the floppy started working again.

• I figured it must be an issue of the DIP switches on the motherboard being configured for hard drive usage.

• The computer manual I got with the purchase provided instructions for DIP switched 1-2 and 5-8, but conspicously left out any mention of 3 and 4, as well as any DIP instructions for hard drives.

• I noted that 3 was set to on and 4 was set to off, so I switched both off and voila, the 3.5” floppy drive now works fine!