Unique S-100 computer (Z-80/Vector Graphic/Micropolis)

[nullvalue]

So I'm pretty certain this is a Vector Graphic S-100 computer but I haven't seen any others like this with the built-in CRT display. I know nothing about this machine. It came with a Micropolis 1053-II disk drive. Would this computer have originally ran CP/M? I'm going to do a lot of cleaning before trying to power it on. How would I go about testing it?

 

[exidyboy]

Micropolis also had their own DOS called, unsurprisingly, MDOS - so that might be another possibility.

 

[nullvalue]

Some cleaning has revealed it is a Cincinnati Milacron "George" computer, or similar.

 

[nullvalue]

After checking the power supply voltages, I went ahead and booted it up. The screen is bright & clear, however all I get is a block of random characters..

 

[deramp5113]

The ribbon cable for the floppy drives is still there, but the Micropolis floppy controller is missing. This system could run CP/M or MDOS. The version of VG PROM monitor will also help know what it ran. What exactly is shown in the two EPROM labels?

The system has 56K or RAM (48K + 8K) so most likely it is a version 4.x monitor. The Micropolis controller would have been strapped at F800h See https://deramp.com/downloads/vector_graphic/software/disk_images/Micropolis controller/ReadMe.pdf for a bit more info.

Mike

 

[deramp5113]

That’s actually a very good first power-up! The CRT, CRT driver, and video boards look like they’re probably all good. They are typically more difficult to troubleshoot than CPU and memory. The VG PROMs only need the 1K RAM on the PROM/RAM board in order to run, so I’d focus on the PROM/RAM board and CPU board first.

Mike

 

[nullvalue]

The ribbon cable for the floppy drives is still there, but the Micropolis floppy controller is missing. This system could run CP/M or MDOS. The version of VG PROM monitor will also help know what it ran. What exactly is shown in the two EPROM labels?

The system has 56K or RAM (48K + 8K) so most likely it is a version 4.x monitor. The Micropolis controller would have been strapped at F800h See https://deramp.com/downloads/vector_graphic/software/disk_images/Micropolis controller/ReadMe.pdf for a bit more info.

Mike

You're right - there was no Micropolis controller in there - the ribbon cable was just hanging inside the case.

The 12K PROM/RAM board has 2 chips installed. "VG MON VERS 4.0" - one marked "#0 E000" and the other marked "#1 E400".

I agree, I was glad I at least got something when I powered it on. So how would I go about testing this board? Even when I left only the Flashwriter in there, I got the same garbled screen. How would you suggest troubleshooting?

 

[glitch]

The Vector 3 was a similar system, from Vector Graphic of course. If it's a Cincinnati Milacron product, that'd certainly explain the industrial-ish design: they made NC and CNC machine tools.

 

[deramp5113]

The display you’re seeing is from the uninitialized video RAM on the Flashwriter. The fact you’re seeing that display means the Flashwriter is probably OK and the CRT driver and CRT are good. The code in the monitor PROM that would initialize the display RAM is not being executed upon power on/reset. This could be due the CPU board or the PROM/RAM board. Do you have another S-100 system you can put the PROM/RAM board in and test it (e.g., see if you can dump the PROMs, access the 1K RAM)?

Mike

 

[nullvalue]

Do you have another S-100 system you can put the PROM/RAM board in and test it

I do not, this is my first S-100 system of any kind. I'll try to get some hi-res shots of the boards up here.

 

[nullvalue]

Here are some pictures of the boards that were installed. Some of the boards looks like the traces are "bubbling" - not sure if that's corrosion or just the mask layer? The Bit Steamer looks almost like an early prototype with a number of corrections/jumpers.

 

[nullvalue]

Can anyone tell me what the power supply voltages should read? There are 4 GND leads going from the power supply to the bus board. Depending on which GND line I use, I get different voltages. Here's a chart of the values I'm getting - does it look right?

	WHITE	RED1	RED2	RED3	BLUE	PURPLE
GND1	0	11v	11v	11v	0	0
GND2	0	11v	11v	11v	0	0
GND3	0	0	0	0	-19v	-20v
GND4	0	0	0	0	20v	19v

 

[nullvalue]

Here are some pictures of the boards that were installed.

vBulletin seems to have compressed the images.. higher resolution here: https://imgur.com/gallery/hUzUsaq

 

[deramp5113]

From what I see, the boards look fine. The bubbled solder plate under the solder mask on the bottom side of the board was not unusual. The Bitstreamer is the original version of their later Bistreamer II board, but from what I can tell in the pictures, the jumpers you’re seeing are just for setting the address of the board and for configuring serial I/O.

I’d say the first step is to get the CPU to jump into the monitor in EPROM and see the monitor initialize the screen and put up the command prompt. Try this with just the CPU, PROM/RAM, and FlashWriter cards installed. If this works, then one of the cards you pulled out is causing a problem. If you still don’t get a good startup screen (most likely), then check the output voltage of each regulator on the CPU card and PROM/RAM card and let me know what you measure.

Mike

 

[nullvalue]

I’d say the first step is to get the CPU to jump into the monitor in EPROM and see the monitor initialize the screen and put up the command prompt. Try this with just the CPU, PROM/RAM, and FlashWriter cards installed. If this works, then one of the cards you pulled out is causing a problem. If you still don’t get a good startup screen (most likely), then check the output voltage of each regulator on the CPU card and PROM/RAM card and let me know what you measure.

Thanks I'll give that a shot and will take some measurements.. I did try that once already. This may be a silly question, but does it matter in which physical order the cards are installed? I seemed to get different garbled screens depending on the order of installation.

 

[nullvalue]

check the output voltage of each regulator on the CPU card and PROM/RAM card and let me know what you measure.

Ok, I have booted a number of times with just those 3 cards in and it hasn't got me a prompt. Most of the time I get the static screen I previously posted. Sometimes I get an instance where screen has characters "dancing" around, mostly 9's inverting with = signs and other odd stuff. Nothing very promising looking..

The voltage regulators all seem the check out..

Z80
7805: 4.88v

PROM/RAM
7905: -5.13v
7905: -5.04v
7812: 12.04v
7812: 12.07v

 

[deramp5113]

What about the 5v regulator on the PROM/RAM (upper right corner)?

Mike

 

[nullvalue]

Oh I measured that one, forgot to write it down - looks good. 7805: 5.02v

 

[MikeS]

...does it matter in which physical order the cards are installed? I seemed to get different garbled screens depending on the order of installation.

It shouldn't; it might be worth while to clean up the card edge connectors with a soft eraser, spray the sockets with Deoxit or an equivalent contact cleaner and work the cards in and out a few times.

An interesting system to be sure; I have the opposite: a set of Cromemco cards in a VG MZ chassis ;-)

 

[nullvalue]

it might be worth while to clean up the card edge connectors..

Thanks I'll give that a shot.

Its evident there was a floppy controller in this machine at one point but was removed. Is it possible its somehow hard jumpered to boot from floppy? Or are these systems supposed to boot to the monitor every time/or boot failure?