View Full Version : Two Mystery Zenith's

August 15th, 2003, 12:47 PM
I am on track in picking up two Zenith desktop computers with monitors. The are both the same system model (unknown at this time), have two half-height 5.25" floppy disks, and operate on a backboard bus-type sustem, with the CPU on a card, and such like that. Both have AMD 8088 CPU's and keyboard/floppy cards, but no video cards or any other periphrials. The monitors are about 8-10" in size and are green monochrome. There are no matching keyboards, unfortunately.

Can anyone tell me about these systems, like are they CP/M or DOS compatible? Where can I find info about this perticular system, or even pictures?

Thanks in advance.

August 23rd, 2003, 03:56 PM
Sounds like they may be Z-150's.

Look on the back and see if you can find anything indicating a model number. If I remember correctly, that particular line had a model number something like this: 151-DVX-??? It's been several years since I did any work on those, the Navy finally upgraded!

Another source is compuserve's vintage forum. Doc Bogner is a tremendous wealth of knowledge on the Zenith line.

I believe compuserve is available via web without subscribing.


August 23rd, 2003, 08:20 PM
I believe compuserve is available via web without subscribing.

If it is, I haven't figured out where. . .

If anyone knows, I'd sure like to see what's there.


August 24th, 2003, 02:58 PM

Just went there and after wading through screen after screen until I finally got to the forum page and selected the "V" for Vintage Computers, I set up a new screen name entirely unrelated to my normal account, at no charge.

Now that I've proved I can get there from here, I may just cancel my paid account!

August 25th, 2003, 02:48 PM
Well, I've tried finding some pics of the Z-150 on the net, without success. Can anyone tell me a bit more about these machines? Like how common are they, perhaps? All I know about them is that they can run both PC-based OS's and CP/M OS's.

August 26th, 2003, 02:53 PM
Z-150's were NOT CP/M compatible. Strictly 8088 machines. I know this for a fact due to the fact the U. S. Navy (my employer) bought about a gazillion of them in a RF reduced format.

If your machine has a Z80 or 8080, then it definitely not a Z-150!

Still think your best bet will be Doc Bogner over on compuserve.


August 26th, 2003, 02:54 PM
Okay, stupid question. Is this an all in one unit, ie with the monitor built in?

If so, then your model number is Z-120! And that did come in a dual processor configuration.


August 26th, 2003, 03:15 PM
Nope. It's a desktop computer with the tower/case seperate from the green monochrome monitor, which is quite small! Only about 8-10", I'd say.

None of the machines have a video card though... could be a problem.

August 27th, 2003, 02:58 PM
Hmmm. Definitely going to need more information.

Is there any sort of identifying info on the back/bottom?

August 27th, 2003, 04:11 PM
I didn't have the chance to look them over thouraghly yet, but will once I buy them, hopefully next week.

August 27th, 2003, 06:12 PM
have two half-height 5.25" floppy disks, and operate on a backboard bus-type sustem, with the CPU on a card, and such like that. Both have AMD 8088 CPU's and keyboard/floppy cards.

That sounds like the computers I bought about ten years ago at an auction. Are the cards taller than average? I bought 24 of them for $9.00

August 29th, 2003, 11:49 AM
I finally got those two Zenith's home. What sort of numbers would you need to help me identify them and where can they be found on the machines?

Both will boot into an OS which I have never encountered before, "MFM-1200" and "MFM-600". I don't know how to do anything else on them, hehe.

August 29th, 2003, 03:58 PM
Both will boot into an OS which I have never encountered before, "MFM-1200" and "MFM-600

I assume that you mean one boots to a MFM-1200 prompt and the other to a MFM-600 prompt?

Have you opened the boxes to see what chips are there?

Do they go through a POST? (power on self test) Do you see access to first to one floppy, then the other? Are there any other messages on the screen? (such as memory counting)

Have you tried powering on with a MSDOS bootable floppy in A:?

August 29th, 2003, 05:55 PM
Well, out of the two I have made one fully functional one, which will be of primary focus:

I knew I forgot something before putting the case covers on, but the operational one working now has a CPU board with 640KB of memory on it. I'm pretty sure it has -both- an AMD 8088 and some type of other processor (what I think is a processor) that said "Z39" or something like that.

It doesn't go through any type of a post procedure that I can see on startup. It goes to access the floppy drives (first A: then B:) then will give me an error concerning the floppy disks - with or without an MS-DOS boot disk in it. At that point, I press escape which brings me into a type of OS which I am not familliar with.

September 15th, 2003, 12:46 PM
I just happened to have Andy Molloy's copy of "Collectible Microcomuters" by Michael Nadeau. It describes a total of a dozen Zenith computers starting with the Z90 and ending with the Z181 and mentions the laptoo and notebook series in the late 80's and early 90's. All but two of them are based on 8088 or better Intel chips. The Z90 was the H-89 they acquired from Heath, with the Zenith name on it. The Z-100 wasa dual processor/operating system computer with an 8085 with CP/M-85 and a 5 mhz 8088 running ZDODS, Zenith's version of MS/.DOS.I remember that one because I did some consulting work for a company that was developing some interesting course-ware for it.) The Z-150 is pictured and described in the book but sounds nothing like the machine discussed in this series of responses.

September 17th, 2003, 02:27 PM
I was thinking about the problem today and it suddenly occured to me that they may be H-89's which they might have sold in Europe and Canada to the educational market, with a "Zenith" name on them.

Ray Borrill

Terry Yager
September 19th, 2003, 10:04 AM
The MFM-xxx program is a system monitor or "software front panel" which is useful for a variety of functions. To see a list of available commands hit the question mark at the prompt. One of the commands is the "B" command which causes the computer to boot from the bootable drive. If that does not work it probly means that yr floppy subsystem is not working.