Heath/Zenith Z90

Heath/Zenith Z90, ca. 1981

CPU: Z80 @ 2MHz
Floppy Drives: 2 Teac FD-55F-030U quad-density (720KB each)
Display: 12" Green (25x80)
Ports: 3 RS-232
Model: Z-90-82
Serial No.: J143G060
OS: CP/M 2.2 or HDOS
Original Price:

This system has a double-density controller (Z-89-37), and an additional 16KB memory board (85-2359-1) to take it to a full 64KB. It echoes characters perfectly in offline mode, but the processor board doesn't appear to work at all.

Update (09/14/2014): On checking voltages, I found that the -12V line was down close to -1V. I traced that to a shorted 2.2uf tantalum capacitor (C511) and replaced it, along with several other tantalum caps on general principles. The -12V line now looks good, but the CPU board is still not initializing properly.

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Last updated on Sunday, September 14, 2014