Repairing a defective Olivetti M21
Olivetti S.p.A. is an Italian manufacturer of computers, tablets, smartphones, printers and other business products such as calculators and fax machines. Headquartered in Ivrea, province of Turin, the company has been part of the Telecom Italia Group since 2003.
The primacy of the first PC can be assigned to Olivetti thanks to Programma 101, which was produced in 1964 and had a big success in the U.S. market.
Olivetti’s first modern personal computer, the Olivetti M20, featuring a Zilog Z8000 CPU, was released in 1982. In 1983 Olivetti introduced the M24 and in 1984 the M21 (the first and last of transportable of Olivetti), a clone of the IBM PC using DOS and the Intel 8086 processor (at 8 MHz) instead of the Intel 8088 used by IBM (at 4.77 MHz).
The M24 was sold in North America as the AT&T 6300. Olivetti also manufactured the AT&T 6300 Plus, which could run both DOS and Unix.
The comparison (before / after):
Repairing & things before of the Cleaning:
- Mirror image.
- Sometimes garbled image with using the ISA Bus.
- Replaced a 74LS245N on the motherboard side.
- Replaced a 75LS244N on ISA expansion Module.
- Removed the battery for the Realtime Clock.
- Bios v1.36 to v1.43 (latest).