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Old 10th Oct 2018, 11:02 pm   #26
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Default Re: 486 PC. Keyboard problem.

UPDATE.

I removed the PC from the control cabinet, placed it on the bench and reseated everything in sight.

I then connected mains, a VGA LCD monitor (the machine uses a CRT monitor) and a keyboard. Put an MS-DOS start up disk in the FD drive and switched on.

The PC complained about the FD, so I produced another one. Then PC then booted up correctly about 20 times. I thought I'd fixed it!

I put the PC back in the control cabinet and connected it to the CRT monitor and the mains supply inside the cabinet. The same keyboard was used throughout. Nothing else was connected to the PC, which actually controls the machine via a com port.

The PC booted up once and then went back to its old tricks. I powered it from a wall socket rather than from the supply in the cabinet and connected the LCD display instead of the CRT one. Still no joy.

There is no difference electrically between this and the bench set up.

Physically the PC was horizontal on the bench, but is vertical in the control cabinet. Also the PC case is screwed into the control cabinet, so I suppose something could be distorting.

I'll have it back on the bench tomorrow.
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