Arrived:

Desoldered the remains of the battery and did some wet cleaning on the bottom part:

And did a quick test:

Survived 😀

Much work left to do. Need to find a way to remove the rust from the case. But already can say that everything works and this was a good deal 😀

Predator99 wrote on 2020-02-21, 10:01:

Desoldered the remains of the battery and did some wet cleaning on the bottom part:

That looks delicious.

man you dodged a bullet with that battery, amazing it didn't damage any traces or vias

liqmat wrote on 2020-02-21, 16:06:

That looks delicious.

batt on the barb.jpg

🤣 nice picture!

Yes I was really lucky with it. Seems the battery (lithium?) only triggered the formation of rust on the case...

That BIOS is neat. Simply love that 50Hz/60Hz video option! ^^

Yes, also happy that the content of the EPROM is still there as it came without a sticker...will dump it later and upload.

I have found some more data about this PC. Its the Zenith Z-200 / Z-248

Mainboard at Stason
https://stason.org/TULARC/pc/motherboards/Z/Z … 6-Z-248-12.html

Manual and Diag disc:
http://www.mediafire.com/file/fizkmlyjnzw/Z200.zip/file

Three machines in that ad I knew these from back in the day when I helped with computing dept.

Images of these monitors; this was zenith's development of flat CRT monitors. They came with a cooling fan at the rear bottom blowing upwards from the under with inlet vents in the sloped rear area. Multiple boards, bottom, sides and rear and on top. Old tech. Heavy too.

They failed frequently. When they worked, they look really nice. Eventually other competitors came up with their much better reliable , one motherboard design, cooler running, flat CRT monitors fully 20 years later, more plentiful is Samsung. I fixed them these when I was working at electronics shop.

Cheers,

that battery has seen better days x3

can you get the gunk off the cards without damage?

imi wrote on 2020-02-21, 21:38:

that battery has seen better days x3

can you get the gunk off the cards without damage?

Just made a cleaning attempt. For the MFM controller the damage shouldnt matter as the ROM is not populated.

For the EGA/VGA I dont know. Think I will it a try as is. The rust is no conductor therefore there should be no risk of shorting something...

Before:

After:

Made some progress. Further cleaned the EGA/VGA with WD-40, now the rust is almost gone.

Tested both cards and they are running.

Also connected the ST-251. Unfortunately its not spinning up at all and when shaking I hear some clicking sound from the inside - there seems to be a loose part. Thats sad, I was very curious what is stored on the disk...

The best news is the BIOS. This one gets the award for the coolest 286-BIOS I have seen so far. Believe or not, is has an integrated DEBUGGER!!!

I will verify my dump in PCem before uploading...maybe this one is also running in other 286s, will test this...would be really cool!

nice 😀

BIOS here:
80286 BIOS image collection

Its 64k in size, so it does not run in PCem, but I verified the image.

The Zenith 248 was one of the most common PCs used by the US Air Force. I would bet they had many thousands of them. Not sure if the one you are getting was an Air Force computer, but it's statistically probable.

So I did a very quick opening of the ST-251 to remove that loose part and take a photo. Didnt see it falling out but is away now. I assume the top head had a crash and will not work anymore.
Dont know if the head is still OK but these scratches shouldnt be there. Compare these pcitures:
http://www.computerasylum.co.uk/storages/st251/index.html

The disc is spinning up now and I am currently making an image with many many bad sectors....already took a look at the directory structure and content seems not to be military related 😁

Zenith systems were very well engineered - I guess that's why they held such favour with the defence industry. I've got a Z-159 (rebadged as British Telecom), which also has the debugger (built into the 'monitor' ROM - also has some test routines. Very nice system you have there.

Talking about military zenith PC, wanted to add:
I worked on one of zenith boxen that is based on passive slot board with voltage LED status and 8088 specific cards along with regular cards. It was encased in TEMPEST spec box in a box with power filters box with toroidal wound inductors for each voltage output then a metal partition pierced by dielectric pass throughs then toroidal inductors all in a box attached to PSU's side the for PSU's outputs. Also the i/o signals are also filtered with these devices too.

Cheers,