Holborn 6100 working again!

[Roland Huisman]

Hello Everyone, I've got my Holborn 6100 computer working again.

Here is al little story about Holborn and the repair of the Holborn 6100
You can also watch the machine on http://youtu.be/H-xoC5zRjjE

A little story about Holborn computers. Holborn was founded in 1979 in Hengelo. (In the Netherlands)
This was their first building, but soon it was to small.



They built a new and bigger building in Enschede. Here you can see the production room.
For the first 9100 series machines they used Beehive terminals. You can see these
terminals at the front. Their core business was the system unit itself. These had a
Holborn mainboard. In later machines they used their own hardware for the terminals.



Holborn tried to make a difference in design and flexibility. The first machines
were running HOS. (Holborn Operating System). Holborn made special software
for dentists and jewelers. Flexibility was the key in those days.

But CP/M became more and more standard, so they began tu use CP/M as well



And then, the IBM monster came. It killed almost every small computer company.
Many systems were dumped. But some were saved for years in the attic:



And after a LOT of cleaning and removing nicotine it looked like this:

 

[Roland Huisman]

The next thing was to get it working again. Let's open the machine.

You can see here the main board, a terminal board, SASI interface
power supply and keyboard.



The keyboard has a lot of not working keys. The problem was the aged foam.
This process had also damaged the aluminium layers of the capacitive contacts.



So a lot of new contacts were made out of a rubber layer, aluminium tape and scotch magic tape.



But still there was a group of not really important keys which did not function.
These keys had 2 common lines to a scandriver chip. Well I used it a while
and suddenly, after a power on, the total keyboard stopped working.

The problem was the scan IC itself. After replacing it the keyboard worked normal again.
An even the earlier not working keys started to work again.



Lets have a look inside the machine. At the bottom there is the main board.
Above this board is a terminal board. The grey coloured PCB is the SASI interface.
And at the top on the left, there is the power supply.

 

[Roland Huisman]

In the power supply there are some mains filter caps. I know they can burn at 115V.
But we have 230V here. These caps can easily turn into a smoke canon.
So, these were replaced first.



Here is the Z80 mainboard. The mainboard has all fast comminication ports
like the parallel port, floppy interface and harddisk interfacing.



The motherboard has a lot of modifications on the PCB. The machine had serial no 57.
So probably the first batch of PCB's had to be modified while the software was developed.



There is a 3 wire serial connection between the motherboard and the terminal board.
The terminalboard has functions like a VT100 terminal. It generates the characters,
reads the keyboard and the external serial I/O.



And did they call this piggy bagging?

 

[Roland Huisman]

A hard disk was very expensive those days! The SASI HD interface
has serial number 14. the machine 57. So 1 on 4 machines had an hard disk?



To clean the machine I had to remove the CRT. I've never seen this
construction before. A plastic ring glued at the conus of the CRT.
This ring holds the PCB.




The mask had a weird sticky layer on it. So I cleaned it and
the sticky layer disappeared. But also the paint did disappear.



But a nice new layer of paint made it beautiful again

 

[Roland Huisman]

Now its time for the external case. There is a hard disk interface in the system right?
Well no hard disk here! You can see some plastic holders which used to hold
a power supply and a hard disk controller.. 4 holes were for a 5.25" hard disk.



Here you can see the nice 8" Toshiba floppy drive



After putting a floppy into the drive, the center bearing made a lot of noice.
I've pulled the bearing out and put in some new grease. The noise disappeared



Also here a power supply for the floppy drive only. If you have a 2 floppy system
both floppy units are powered by this power supply. And yes, also dangerous caps.



One of the missing PCB's was a power supply. I've checked a Holborn 6100
in a museum nearby to check what I was missing in the external case.

The power was the same model as in the system itself. A friend of mine had
a similar one but not exactly the same. And different voltages!

 

[Roland Huisman]

Because it was the only power supply which looked the same
I've modified the voltages. I needed +5 and +12V. The 5V was okay.
But the other was +15V. I've modified the transformer to get a nice 12V again.



There were also some cables missing. Holborn uses all black wires in the system.
So I did the same here. But be careful, 5V chips do not like 12V.




The other missing PCB was a Xebec S1410 SASI to MFM controller.
Oldappleguy on the forum helped me getting this PCB. Thanks Steve!

I had an old Quantum 5.25" FH hard disk. A bit new for the machine
but I do not have an other older drive. So the machine is complete!



Everything was build into the machine again.

 

[Roland Huisman]

Was it that easy? well noooooooooooooooooooooooooooo............

I spent a lot of time to get this hard disk working again. It was
impossible to get it work with the software I had with the machine.



After a while I made contact with the original technical designer.
He did not remember how it worked. But he had a newer machine
which used the same software as the 6100. It was only on 5.25" disks.
These disks had exactly the same system as the 8" disks.
So the images from the 5.25" disks were 1:1 useful for the 8" disks.

A special thanks to Chuck for figuring out the disk format!

There was also software for hard disk use. The disks were set to
a Rodime 20MB hard disk. I've used these to get the hard disk working.
But the format and configuration tools were password protected !!!

Some friends with more CP/M experience than me, have hacked the software so it
passes the password question. And now it is possible to get it work with
every model MFM hard drive. (Thanks Theo and Freek!)

The system supports a maximum of 2 partitions of 8MB on one hard disk.
You could use two hard disks in the system.




So far the Holborn 6100 story.

============================================================

I've also got this 6500 model from the designer. This was the newer model.
It has almost the same motherboard as the 6100. The 34 pin FDD connector is added.

It has also the possibility to use an external hard disk / floppy unit.
But I have only the system. So I hope I will find another Xebec S1410
to make this system complete as well...




Regards, Roland

 

[Tor]

I don't like "like" buttons, but I now wish there was a "cheers!" button on this forum!
That was a very enjoyable read, thanks for posting! As someone said the last time a picture of that monitor came up, "it looks like something from a science fiction movie!". The screen seems to be very crisp too, from the photos (and makes it easy to spot the original software writer's problem with plurals.. )
The system looks fantastic. Both of them!

-Tor

 

[angel_grig]

I don't like "like" buttons, but I now wish there was a "cheers!" button on this forum!
That was a very enjoyable read, thanks for posting! As someone said the last time a picture of that monitor came up, "it looks like something from a science fiction movie!". The screen seems to be very crisp too, from the photos (and makes it easy to spot the original software writer's problem with plurals.. )
The system looks fantastic. Both of them!

-Tor

Exactly what I wanted to say!!
Excellent presentation Mr Huisman!One of the most futuristic looking computers I've ever seen!

 

[harry]

Excellent and interesting machine , you certainly have put some time and effort into getting it operational well done! Really great looking machine.
... as they say...effort = reward!...........Harry

 

[Roland Huisman]

Hello Tor, Angel_grig, and Harry,

Many thanks for the nice compliments!
It makes it worth to write such an article :D

Regards, Roland

 

[tingo]

Very well written - thanks! I add my praise to the others; well done with both the machine and the article.

 

[Roland Huisman]

Hello Torfinn, Thank you! :D

Regards, Roland

 

[VintageC]

Hoi Roland,

Nice to see a fellow dutch guy made such a beautifull system. You really have a lot of experience and I enjoyed reading this post. Also a lot of nice pictures. Keep up the good work!

 

[leeb]

Fantastic read and AWSOME looking machine!
:D

 

[Roland Huisman]

Hello VintageC and Leeb,

Thanks for the compliments :D

Regards, Roland

 

[Denniske1976]

There's one for sale on MP... not yours? They look very cool

 

[Roland Huisman]

Hello Denniske1976,

I've also got an private message with the tip that there is one for sale.
That is not my machine. It's also not my intention to sell it al all.

But I really wonder if there is some interesting software with it.

In the meanwhile I've got very much information and a lot of
source code for the machine. Even the schematics. And MP/M!

Regards, Roland

 

[VintageC]

There's one for sale on MP... not yours? They look very cool

Im interested in this system but im not sure if I got the knowledge to fix it if its broken.
The seller told me he never tested the machine and was not intended to do so.

What do you think its worth Roland?

 

[Roland Huisman]

Im interested in this system but im not sure if I got the knowledge to fix it if its broken.
The seller told me he never tested the machine and was not intended to do so.

Well for me the most important thing is if it's complete. The electronics is quite straight forward.
There are no tantals used. Only nice ceramic caps on the boards. Electrolytics are good.
The only caps you should replace are the Rifa filter caps. Further: I have all information you
possibly should need for you. Documentation, software, ROM images you name it...

What do you think its worth Roland?

That is a very difficult question. There is no collector sales history for these machines known.
But let me help a bit. Here is an overview of the production in 1982.


(Please note the table is cumulative, so every month they added the previous month)

As you can see they started the 6100 production in Feb 1982. From February until December there were 71 built.
On the 27th of April 1983 Holborn bankrupted. A little guess is that they built another 30 machines
in the last months. That makes about 100 x 6100 machines total. The highest known serial number in existence is 94.
(This particular machine is proprietary of an old Holborn employee.)

So if there is about 10% left of the machines after 30 years, that makes 10 units total in existence.
I guess you won't find a second one...

So what do you think it's worth?

Regards, Roland