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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 6th Oct 2018, 9:19 pm   #1
Station X
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Default 486 PC. Keyboard problem.

At the moment I'm trying to get a CNC lathe dating from 1996 working. It was sold as not working, spares or repair. If I succeed in fixing it I'll have got a bargain, if not I'll have a heavy and expensive door stop!

After fixing numerous wiring and switch faults I've finally got the built in 486 PC and CRT display working. However it stalls in the BIOS before accessing the drives.

Initially it reported a flat CMOS battery, but fitting a new one fixed that. Now it's reporting:-

CMOS system options not set.
CMOS display type mismatch.
Keyboard error.

RUN SYSTEM SET UP
Press F1 to resume.

Needless to say pressing F1 does nothing, but I don't think it's a keyboard fault. The keyboard is a non standard one laid out so that the machine can be jogged etc. It connects via a 10 way ribbon cable to an unidentified card plugged into an ISA?? slot on the motherboard. Also connected to this card is the floppy disk drive. I suspect that the BIOS has to be set up to recognize this card and of course the setting have been lost due to the battery failure.

There is a keyboard socket mounted on the motherboard with nothing connected to it. The BIOS has probably detected this and hence the error message.

The keyboard socket looks like a five pin DIN type and I haven't seen a keyboard with that type of connector for years. Is there an adaptor available I could use in order to connect a USB or PS2 keyboard?

Any other possible solution?

Thanks.
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Old 6th Oct 2018, 9:49 pm   #2
G6Tanuki
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Default Re: 486 PC. Keyboard problem.

There certainly were adaptors available to let you connect a PS/2 type keyboard to an old PC/XT 5-pin-DIN socket. Ages since I last used a computer with either PS/2 or DIN-5 connectors, but it seems that yiou can still buy the adaptors off Amazon, Ebay etc for a couple of quid.

https://www.reichelt.com/gb/en/adapt...1-p179857.html for example.
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Old 6th Oct 2018, 11:26 pm   #3
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Default Re: 486 PC. Keyboard problem.

The standard size 5 pin din connector on a keyboard was known as an 'AT' keyboard.... IIRC .So when dealing with computer scrap dealers the 'AT' keyboard is the one you want.
Large din to mini din (keyboard) plugs were available and also mini dins on a back blanking plate you could just plug into the board were also about
(when the change over from the 'AT' board to the more familar 'ATX' was happening) at Maplins etc.. but obviously not much call for them today..or Maplins...somebody though must have a few knocking about?
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Old 6th Oct 2018, 11:50 pm   #4
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Default Re: 486 PC. Keyboard problem.

Thanks both. I've ordered an adaptor lead.
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Old 7th Oct 2018, 6:57 am   #5
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Default Re: 486 PC. Keyboard problem.

I've no idea how your system works but I have seen similar devices where you need a standard keyboard to set it up. Once all the parameters have been re-set, which probably includes initialising the built-in keyboard, you unplug the setup keyboard so that the settings cannot be changed.
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Old 7th Oct 2018, 8:35 am   #6
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Default Re: 486 PC. Keyboard problem.

That's correct. The BIOS settings will have been configured at the factory. They've been lost though as the CMOS battery had gone flat. Actually it had swollen!

The application software runs under DOS and one of the files tells the application where to look for the built in keyboard etc. One of the buttons on the built in keyboard enables an external keyboard to be selected. However the external keyboard (which I don't have) has the same layout as the built in one.

Next step is to get a DOS prompt!
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Old 7th Oct 2018, 2:56 pm   #7
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Default Re: 486 PC. Keyboard problem.

I would expect you are on the right lines. Always made me smile to see keyboard error press F1 to continue. There will be a setting somewhere in BIOS to either switch off the check, or stop it halting with the error.
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Old 7th Oct 2018, 6:27 pm   #8
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Default Re: 486 PC. Keyboard problem.

I never saw anything strange about "keyboard error or keyboard not present, press F1 to continue" -- it was always obvious to me that there was an implicit "sort out the keyboard problem first" hidden away in that sentence. Apropos of nothing, I have never read "misled" as anything but "mis-led", either .....
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Old 8th Oct 2018, 12:08 pm   #9
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Default Re: 486 PC. Keyboard problem.

Quote:
Originally Posted by julie_m View Post
I never saw anything strange about "keyboard error or keyboard not present, press F1 to continue"
Once upon a time using a computer required people to think. Remember the DOS appendices which included useful information such as the format of .exe and .com files and the hex codes for different partition types? Nowadays I suspect people wouldn't have a clue what you are talking about but at the time it was useful information to have. As for pressing F1, I think the POST just produced a list of errors it had found such as disk missing or something, and then added "press F1 to continue". That wasn't really logical if the keyboard wasn't plugged in but we knew what was meant (but then again, once you had mended the keyboard the error disappeared and it didn't stop to let you press F1). Maybe it was just the programmer having a joke. I suspect there was also an error for monitor not attached but there was no easy way to find out.
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Old 8th Oct 2018, 1:54 pm   #10
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Default Re: 486 PC. Keyboard problem.

I'm surprised at the number of replies to this thread.

All I needed was an adaptor lead and I could have Googled for one. However I thought perhaps one of the experts here might know of a work around.

This PC has no HDD (something I may remedy) and runs the application from an FD. Looking at the files on the FD I can see the familiar AUTOEXEC.BAT and CONFIG.SYS. I'm familiar with BIOS and CMOS, but my knowledge may be a bit rusty by now.

The ironic thing is that, as an anti-hoarding measure, I threw away several keyboards with the correct plug several years ago along with some hard drives. I'm sure a lot of us have been there!
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Old 8th Oct 2018, 3:36 pm   #11
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Default Re: 486 PC. Keyboard problem.

I was once asked to fix a paste oven. It had a 386 in it with a floppy drive to boot from.
The stupid bit was that for years they had been booting it from the floppy even though there was a HDD in it.
It sure was booting from the HDD after I had finished fixing the thing.
The even more stupid thing was that the company went bankrupt and HMRC sent in bailiffs whom found out that it was a leaded solder model that was worthless after they took it away.
They got told in short order to employ better bailiffs. There was no come back after that.
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Old 8th Oct 2018, 4:19 pm   #12
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Default Re: 486 PC. Keyboard problem.

Going off topic I know, but you're going to have to tell me what a paste oven is. Do you mean pasty? Pastie to our Australian members.
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Old 8th Oct 2018, 4:39 pm   #13
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Default Re: 486 PC. Keyboard problem.

A solder paste oven for SMD boards.
It was an old leaded solder one.
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Old 8th Oct 2018, 4:45 pm   #14
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Default Re: 486 PC. Keyboard problem.

Thanks.

Google failed me for once.
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Old 8th Oct 2018, 6:14 pm   #15
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Default Re: 486 PC. Keyboard problem.

For completeness sake: there are basically 4 types of PC keyboard.

- PC and XT: 5 pin DIN, unidirectional protocol
- AT: 5 pin DIN, bidirectional, same protocol as PS/2
- PS/2: mini DIN, bidirectional, same protocol as AT
- USB: similar protocol but entirely different hardware layer

AT and PS/2 are always interchangeable with a suitable adapter cable.

Some USB keyboards might have hardware support for an adapter cable as well, but only if it was explicitly built in.

Some mid to late 1980's aftermarket keyboards might sport a switch in the back or on the bottom to switch between XT and AT modes.
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Old 8th Oct 2018, 9:07 pm   #16
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Default Re: 486 PC. Keyboard problem.

Quote:
Originally Posted by Station X View Post
However I thought perhaps one of the experts here might know of a work around.
The workaround is to disable it in the BIOS, once you get the adapter. It's a passive device; if you had a female 6 pin mini DIN and a male 5 pin DIN you'd be able to knock up a quick temporary fix.

Quote:
Originally Posted by Station X View Post
This PC has no HDD (something I may remedy) and runs the application from an FD.
A good option may be an IDE-CF adapter - they are cheap as chips (I grabbed a couple from the NZ vintage computing Facebook group for NZ$5 each). Dead network security appliances (such as the Netgear UTM series) can be a good source of smallish CF cards.
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Old 10th Oct 2018, 10:47 am   #17
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Default Re: 486 PC. Keyboard problem.

Hi.

We just got this in a pile of bits to dispose of. Its measures 11 inches by 5 1/2.

Yours if you want it.

Regards,

Wayne
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Old 10th Oct 2018, 12:48 pm   #18
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Default Re: 486 PC. Keyboard problem.

Thanks for your kind offer and picture of the keyboard Wayne, but I won't be needing it. I hope I don't sound ungrateful.

The adaptor lead arrived this morning and I used it to attach a PS2 keyboard to the PC. Now, when I switch on, the keyboard error message has disappeared, but the two other errors are still present. Pressing F1 brings up the BIOS configuration screen.

Hopefully after changing BIOS settings I'll be able to get a DOS prompt.

I'll report results here.
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Old 10th Oct 2018, 4:22 pm   #19
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Default Re: 486 PC. Keyboard problem.

Not exactly successful I'm afraid. I managed to enter the BIOS and set up the monitor and floppy disc drive. That got rid of the remaining error messages. I'm using a DOS start up floppy disc created on an another PC for testing.

However the PC has now started to freeze at various points during the boot sequence and only once have I got to the stage where I was able to type "dir" at the DOS prompt and see a listing of the files on the floppy.

The PC typically freezes after testing the memory, just before accessing the floppy disc drive, whilst loading files from the floppy disc drive or after reading the files from the floppy disc drive.

The problem may be temperature related. The 486 CPU has no fan, but there is a forced air draught through the control cabinet which houses the PC and all other electronics associated with the CNC lathe.

I'm beginning to think I'm expecting too much from a PC which is at least 22 years old. Next step will be to reseat all socketed ICs and ribbon cable connectors.

No sign of bulging caps on the motherboard. They're mostly tants.
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Old 10th Oct 2018, 6:13 pm   #20
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Default Re: 486 PC. Keyboard problem.

Chips do get loose on those old motherboards. Give it a go.
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