9 May
1999
9 May
'99
12:24 p.m.
We actually have 3 of the wee beasties, one badged Heath, one badged
Zenith, and one badged Heathkit.
On Sun, 9 May 1999, Tony Duell wrote:
M. K. Peirce
Rhode Island Computer Museum, Inc.
215 Shady Lea Road,
North Kingstown, RI 02852
"Casta est qui nemo rogavit."
- Ovid
I picked up a Zenith Data Systems all-in-one box from the trash a few days
ago. Lovely cosmetic condition. Unfortunately there's no response on the
monitor. The fan spins up so it is getting power. Other than the Heath address
on the back it has no model #. It looks like the pictures I have seen of the
Z-100. Do the first models of Z-100 have a model # on them ?
It has a siemens fdd and a really nice FD image decal labelled Xidex. The rear
sockets are labelled DCE and DTE , connected to a serial I/O daughter card,
FR-1 a 34 pin socket FR-2 a40 pin which are connected to a Disk Interface
daughter card and the fdd has a daughter card Disk I/O and a free hanging
connector for an external floppy. The serial I/O is hard wired to another card
labelled Albrektson Sound/Clock H-89 which has a lead to an external RCA
connector Cassette I/O as well as a battery pak and a mini-speaker.
There is a video card on the bottom. The vertical mounted motherboard has pins
for 5 daughter cards and a Z-80 CPU. There's 48 k mem and an additional 16 k
daughter card.
Another card the same dimension is mounted behind the MB and is labelled
Terminal Logic. It also has a Z-80 as well as a Motorola 6845L chip.
Any Z-100 people out there ?
This sounds like an H/Z 88/89/90. Not all of those combinations existed,
but the basic differences are that H* are heathkits (and came as kits)
and Z* are Zenith (and came assembled). IIRC the 88 is a cassette-based
machine, the 89 and 90 are both disk based. There's probably some
difference in the disk controller or standard memory between the 89 and
90. But basically they're all the same machine and can be interconverted.
I have the hardware manual for my Z90 system here, and it's roughly as
you describe it. With the cover open, there's the 'terminal logic board'
at the back. This is the board from a Z19, BTW, and is what it says it
is. A terminal that communicates via an RS232 link to the rest of the
machine. All video comes from that board.
In front of that, and parallel to it, is the main CPU board. It contains
a Z80 + monitor/boot ROMs + 48K RAM + logic. Plugged into that on the
left side (furthest from the disk drive) is a little card with an extra
16K of RAM on it (it also is connected to one of the RAM sockets on the
CPU board). On the right side of the CPU board are connectors for up to 3
expansion cards. The middle one is normally a triple serial port (using
8250 chips) for the 3 RS232 connectors on the back. The other 2 are disk
controllers (I have both the hard and soft sectored disk controller in my
machine).
Flat in the bottom of the machine, under the CRT, is the video monitor
analogue board. There's a little board on top of this, under the CRT
neck, that carries the video amplfier.
The PSU is on a heatsink bracket behind the drive. But the terminal logic
board has its own voltage regulators.
The terminal logic board/monitor can work without the rest of the machine
being operational, BTW.
I'd start with the PSU. The fan runs off the mains side of the
transformer, so the fact that it's turning doesn't mean the PSU is
working, unfortunately. Any beeps at swtich-on? There's a speaker run
from the terminal logic board (unless the wiring has been changed for the
sound card you have - if so, reconnect it to P402 (2 pin connector on the
bottom edge of the terminal logic board for the moment).
Here are some voltage testpoints (WRT ground = black wire) :
Floppy disk power red wire : +5V
Ditto orange wire : +12V
P516 (4 pin to CPU board with 3 wires going to it) red wire (3) : +5V
Ditto orange wire (1) : +18V (approx)
P514 (10 pin from PSU to CPU board) :
Green (1) : -18V (approx)
Orange (3) : +18V (approx)
Red (6) : +8.5V (approx)
Across C1 (large electrolytic on main chassis under drive) : 65V
I guess the question is do I try and ressurect
it ? It has such a nice-looking
KB and is in such good cosmetic shape that it would hurt to junk it.
It's quite a nice CP/M or HDOS machine...
If it is a Z90-a-like, I have schematics for the main machine, Z17 and
Z37 disk controllers, RAM card and drive. And ROM listings for the
machine and terminal logic PCB.
-tony