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Repairing an Olivetti M20
This section is intended to provide an help for common problems in old machines like the M20.We do no take any responsibility for damages or injuries occourred when repairing the machine. Dangerous voltages can be present in several circuits, when the computer is connected to the main power. Remember also that several capacitors can stock dangerous energy for a while after the computer has been switched off. If you feel unconfortable using a soldering iron, you should probably skip this section of the site.
For the moment, we can not give a complete description of every possible problem in the M20. Remember that in such an old machine, almost everything can be repaired. It is just a matter of time, patience and skill. Anyway, if you can solve the problem, we would be happy to include a description of your solution.General informations
Taking apart the Olivetti M20 (by Davide Bucci)The power supply unit
The disk drive units
The keyboard
Diagnostic errors
The Olivetti M20 performs a self test at the startup. In case of problems, it prints error messages on the screen and/or on the printer. Those error messages can be useful to identify and solve the problem. Here is a list of the possible error codes that can be shown at the startup.| Message given: | Error condition: |
| Triangle | Test CPU registers and instructions |
| Triangle | Test RAM |
| 4 vertical lines | Test CPU instructions call and trap |
| Diamond | Screen and printer setup |
| EC0 | 8255 error parallel interface | EC1 | 6845 error screen controller |
| EC2 | 1797 error disc drive controller |
| EC3 | 8253 error timer circuit |
| EC4 | 8251 error keyboard interface circuit |
| EC5 | 8251 error keyboard interface |
| EC6 | 8259 error PIC |
| EK0 | Keyboard not responding |
| Ek1 | Keyboard responding, but autotest failed |
| ED0 | Error floppy 0 |
| ED1 | Error floppy 1 |
| E10 | Non vectored interrupt error |
| E11 | Vectored interrupt error |
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This site is no way related to Olivetti nor Telecom Italia
