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:
> >
> > 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
>
>
M. K. Peirce
Rhode Island Computer Museum, Inc.
215 Shady Lea Road,
North Kingstown, RI 02852
"Casta est qui nemo rogavit."
- Ovid
Received on Sun May 09 1999 - 19:24:24 BST
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