BBC Master Compact - Keyboard Headache

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BBC Master Compact - Keyboard Headache

Postby Beaglz on Sun Mar 12, 2017 3:22 pm

Anyone out there had some experience in troubleshooting problems with this BBC?

Issue is with the keyboard (or related to it). Computer powers on (red shows), Caps Lock LED lights up then off, computer beeps then Caps Lock LED remains on. Only key on the keyboard that does appear to work is the 'Break' key. Have pulled everything apart and the internals of the computer look in really good condition. No blemishes on the PCB, wiped down the keyboard PCB to ensure it was clean (looked brand new to start with) and no change.

Have spent a couple of hours looking through Google results and no reference to this type of problem. Have powered computer up without the disk drive connected and same problem.

Next step is probably to check the cable connection between keyboard and motherboard but visual inspection looks fine - no loose wires.

Any other ideas out there?

Cheers,
Beaglz.
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Re: BBC Master Compact - Keyboard Headache

Postby tezza on Tue Mar 14, 2017 2:16 pm

Hmm...just a thought.

The BREAK key was known to be problematic in the BBC micros in that it reset the machine and cleared memory. This is not how the break key behaved in other micros. Usually it just stopped a BASIC program mid-execution (In the BBC the ESC key does this) but didn't delete it. I've heard of the BREAK key being deliberately disabled in BBCs used for schools because so many students automatically pressed BREAK and lost their work.

I just wonder if this was a ex-school micro and the BREAK key has been disabled somehow (cut track, missing IC or other?).
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Re: BBC Master Compact - Keyboard Headache

Postby Beaglz on Tue Mar 14, 2017 4:47 pm

Perhaps not the cause but does explain why there is a drill hole next to the break key and if I use a flat head screwdriver and rotate a plastic tab 90 degrees it stops the break key from being depressed.
All the ICs that are in sockets look to be full seated. Will have another look over the weekend once I get back from CHCH.
Cheers,
Beaglz.
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