HP250


OldHP
 

Hello at all,

I'm new in this group and would like to get in contact with people owning a HP250 or who are familiar with this computer.
Such a computer is used in my museum as a living exhibit .
Am I right here with this theme?

I already tried to contact hpmuseum.net because these people asked for surviving HP250, but never got a response.
Is hpmuseum.net still active?

Best regards
Rüdiger


David Collins
 

Rudiger, we replied to your email on April 3rd as follows..

 

 

 

Hi Rudiger and thanks for making contact. I’ve looked back through our emails and can’t see any previous messages from you, but my suggestion is you ask your questions at the Vinthpcom forum at groups.io.

 

If you can provide the part numbers of the boards in question I might be able to get more info.

 

Do you have a 250A in the desk top style with the 10MB drive built in or the later 250 in the cabinet with separate disc/tape?

 

David Collins

Curator

 

 

 

From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of OldHP
Sent: Wednesday, 20 April 2022 5:41 PM
To: VintHPcom@groups.io
Subject: [VintHPcom] HP250

 

Hello at all,

I'm new in this group and would like to get in contact with people owning a HP250 or who are familiar with this computer.
Such a computer is used in my museum as a living exhibit .
Am I right here with this theme?

I already tried to contact hpmuseum.net because these people asked for surviving HP250, but never got a response.
Is hpmuseum.net still active?

Best regards
Rüdiger


 

@Rudiger

 

Hi there, i have many years of experience with HP250.

I have next to none hardware-  but a LOT of software knowledge.

I would gladly help you if I can.

 

Greetings,

Harold

 

 

From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of David Collins
Sent: Wednesday, April 20, 2022 12:38 PM
To: VintHPcom@groups.io
Subject: Re: [VintHPcom] HP250

 

Rudiger, we replied to your email on April 3rd as follows..

 

 

 

Hi Rudiger and thanks for making contact. I’ve looked back through our emails and can’t see any previous messages from you, but my suggestion is you ask your questions at the Vinthpcom forum at groups.io.

 

If you can provide the part numbers of the boards in question I might be able to get more info.

 

Do you have a 250A in the desk top style with the 10MB drive built in or the later 250 in the cabinet with separate disc/tape?

 

David Collins

Curator

 

 

 

From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of OldHP
Sent: Wednesday, 20 April 2022 5:41 PM
To: VintHPcom@groups.io
Subject: [VintHPcom] HP250

 

Hello at all,

I'm new in this group and would like to get in contact with people owning a HP250 or who are familiar with this computer.
Such a computer is used in my museum as a living exhibit .
Am I right here with this theme?

I already tried to contact hpmuseum.net because these people asked for surviving HP250, but never got a response.
Is hpmuseum.net still active?

Best regards
Rüdiger


OldHP
 

My HP250 has only one FDD (also no cable to add a second) and I only own one floppy disk set to the computer:
so its future currently depends on the survival of the one functional boot disk.

It is urgent to me to create backups: best would be as disk image files to a PC.
I know the solution of Ansgar using a HP-IB card and a 9895A drive, unfortunately I don't own both devices.
But I could use low level FDC's like Catweasel, Greaseweazle or Cryoflux.
The software of these controllers needs to match to the structure/encoding/CRC's of the disk, so I cannot simply use any copy program.
Is there already a way using such controllers for HP250 backups? Or is there a different technology to save HP 8" disks?

Best regards.


 

We're do you live?
Maybe there is a member in your neighborhood who can help you with this.

-Rik


OldHP
 

In Germany. The museum is in Halle (Saale).

I'm already searching for HP250's here, but without success.
Asking local computer forums did not show more exemplars.
The only other HP250 I know at my region has been sold to a dealer and is offered expensive at ebay (175152156665) since that.


 

But you don't need a HP 250 to make the backup, a 9895A with a PC with hpdir should be enough to make the images of the discs. And we have some  members also living in Germany, maybe one of those could help you. I haven't looked up the exact location, so I could be way off, but I like in the north of the Netherlands. If it's in your range you would be welcome. I have a working 9895A in combination with a hpdir setup, so making a backup wouldn't be any problem.

-Rik


OldHP
 

650 km away: too much for a travel. All the most via parcel.

Is there anywhere a description of the structure of the HP250's 8" floppy disk sectors?


Ansgar
 

Guess the 250 is using a 9895K (=9895A w/o PSU and with a different controller) as default floppy drive. The controller is a bit different, but also provides a HP-IB interface and understands the same AMIGO commands as a 9895A. The drive module should be the same, so should be the media format. See http://bitsavers.org/pdf/hp/disc/7902/07902-90030_7902_9895_Svc_Jan81.pdf

-Ansgar


OldHP
 

@Ansgar: Thanks for the link.

My HP250 got a new problem: keyboard does not work anymore (no reaction when pressing any key).
The reason could be the keyboard itself or the keyboard controller (I have no spares of both to locate).

That keyboard has an interesting design: inside each key there are two wire loops with ferrite cores on it.
In unpressed state that loops work as transformers: transporting a ramp signal from one loop to the other.
If the key is pressed, two magnets are moved beneath the ferrite cores and bring them into magnetic saturation: it stops the transport of the ramp signal and is detected by a receiver.
That principle was also used at HP 264xx terminal keyboards: http://www.hpmuseum.net/document.php?hwfile=2538

Now the questions:
Has anybody knowledge about such a keyboard problem?
What happens if a key would be erroneously permanently pressed (I suspect a magnet could be slipped): would it disable all other keys?


 

It's the same principle used by the 9810 and 9820 calculators. There is a signal called key pressed if that's adserted it will hang the keyboard logic.

-Rik


 

On April 23, 2022 12:12:33 PM "Rik Bos" <hp-fix@...> wrote:
It's the same principle used by the 9810 and 9820 calculators. There is a signal called key pressed if that's adserted it will hang the keyboard logic.
This happens with a lot of HP test equipment too. Astuck front panel button will prevent the instrument from initializing, and it will appear to be dead. I've gotten a number of very nice deals that way. ;)

-Dave

--
Dave McGuire, AK4HZ
New Kensington, PA


OldHP
 

On Sat, Apr 23, 2022 at 06:12 PM, Rik Bos wrote:
It's the same principle used by the 9810 and 9820 calculators. There is a signal called key pressed if that's adserted it will hang the keyboard logic.
 
-Rik
I don't understand. Here...
http://bitsavers.informatik.uni-stuttgart.de/pdf/hp/250/45251-90001_HP250sch_Jun82.pdf
...at page 48 (especially at upper left corner) there is the schematic plan of the HP250 board where the keyboard is connected to.
I see many signals but no "key pressed".


 

The first thing to do is removing all boards and connectors and replace them, if there are any socketed IC’s pull them and replace them. This should eliminate the most off the contact resistance. If you’re lucky this solves the problem, probably not but it looks very silly if you tried it after several hours fault finding and the machine works..  The next thing you have to do is checking the ic’s on the keyboard especially the analogue IC 1821-0001 which is a CA3046. Look for non-compliant TTL signals >1V <3V those are suspicious. Next check the output signals to the keyboard J3-5, J3-15 J3-R etc.  J3-10 should be a continuous clock signal even as J3-L. Check J3-9 when no key pressed it should give no signal or a continuous square signal, this is the serial keyboard data in. The signal should change when a key is pressed, I think the SRO signal is the release signal for the keyboard so check it, it should do something.

This should give you some idea of what’s happening.

 

If you have a logic analyzer hook it up to the keyboard signals and look what’s happening.

 

-Rik

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens OldHP
Verzonden: maandag 25 april 2022 14:07
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP250

 

On Sat, Apr 23, 2022 at 06:12 PM, Rik Bos wrote:

It's the same principle used by the 9810 and 9820 calculators. There is a signal called key pressed if that's adserted it will hang the keyboard logic.

 

-Rik

I don't understand. Here...
http://bitsavers.informatik.uni-stuttgart.de/pdf/hp/250/45251-90001_HP250sch_Jun82.pdf
...at page 48 (especially at upper left corner) there is the schematic plan of the HP250 board where the keyboard is connected to.
I see many signals but no "key pressed".


OldHP
 

HP service manual advises to replace keyboard or KBD controller in this situation.
Or to type a BASIC program to test the keys.  :-D

Should anything happen if I press the 8 soft keys at the screen right after boot procedure (while keyboard is unplugged)?




On Mon, Apr 25, 2022 at 09:35 PM, Rik Bos wrote:

The first thing to do is removing all boards and connectors and replace them, if there are any socketed IC’s pull them and replace them. This should eliminate the most off the contact resistance.

I have already re-plugged the boards and the plugs: it does not better my situation.
All IC's are soldered.
May be I could measure the keyboard cable for interruptions.


The next thing you have to do is checking the ic’s on the keyboard especially the analogue IC 1821-0001 which is a CA3046.


To which schematic plan you are referencing? I've not yet found a schematic plan of the keyboard...
In the HP250 service manual I only find a picture of the layout (http://bitsavers.informatik.uni-stuttgart.de/pdf/hp/250/45251-90001_HP250sch_Jun82.pdf ,  Page 49).


Look for non-compliant TTL signals >1V <3V those are suspicious. Next check the output signals to the keyboard J3-5, J3-15 J3-R etc.  J3-10 should be a continuous clock signal even as J3-L. Check J3-9 when no key pressed it should give no signal or a continuous square signal, this is the serial keyboard data in. The signal should change when a key is pressed, I think the SRO signal is the release signal for the keyboard so check it, it should do something.

This should give you some idea of what’s happening.


I will do.
Because I only can sporadic travel to the computer, it will take some days.


 

About the IC’s on the keyboard, at the layout drawing of the keyboard you can read the hp numbers of the IC’s.

With use of the hp part number index you can see what the manufacturing number of the IC is.

This make functional tests possible, measure the input signals against the output signals and check using the datasheet of this correct is.

Even reverse engineering of the diagram is possible this way.

But as far as I understand the diagram on page 48 the controller is providing scan signals (output) which are read back by the /SRIN signal

The /SRIN signal should contain the data of which key is pressed.

The Softkeys are parallel buffered by a 74LS377 and read independently from the keyboard than the signals are multiplexed by U26 which outputs the SRIN’sk signal which is fed thourg a NOR gate with the SRIN signal and becomes the /SRIN’ signal containing the combined keyboard signal.

You could check if your keyboard works if the Softkeys are decoupled.

You’ll need an oscilloscope to check this signals to see if the levels are right and to check if the is no distortion and to check the noise levels.

Keep in mind the TTL-LS (74LS) series is much more noise sensitive as the standard TTL (74xxx) series IC’s

 

-Rik

 

 

 

 

Van: VintHPcom@groups.io <VintHPcom@groups.io> Namens OldHP
Verzonden: dinsdag 26 april 2022 10:00
Aan: VintHPcom@groups.io
Onderwerp: Re: [VintHPcom] HP250

 

HP service manual advises to replace keyboard or KBD controller in this situation.
Or to type a BASIC program to test the keys.  :-D

Should anything happen if I press the 8 soft keys at the screen right after boot procedure (while keyboard is unplugged)?




On Mon, Apr 25, 2022 at 09:35 PM, Rik Bos wrote:

The first thing to do is removing all boards and connectors and replace them, if there are any socketed IC’s pull them and replace them. This should eliminate the most off the contact resistance.

I have already re-plugged the boards and the plugs: it does not better my situation.
All IC's are soldered.
May be I could measure the keyboard cable for interruptions.

The next thing you have to do is checking the ic’s on the keyboard especially the analogue IC 1821-0001 which is a CA3046.


To which schematic plan you are referencing? I've not yet found a schematic plan of the keyboard...
In the HP250 service manual I only find a picture of the layout (http://bitsavers.informatik.uni-stuttgart.de/pdf/hp/250/45251-90001_HP250sch_Jun82.pdf ,  Page 49).

Look for non-compliant TTL signals >1V <3V those are suspicious. Next check the output signals to the keyboard J3-5, J3-15 J3-R etc.  J3-10 should be a continuous clock signal even as J3-L. Check J3-9 when no key pressed it should give no signal or a continuous square signal, this is the serial keyboard data in. The signal should change when a key is pressed, I think the SRO signal is the release signal for the keyboard so check it, it should do something.

This should give you some idea of what’s happening.


I will do.
Because I only can sporadic travel to the computer, it will take some days.


OldHP
 

On Tue, Apr 26, 2022 at 04:45 PM, Rik Bos wrote:

With use of the hp part number index you can see what the manufacturing number of the IC is.

Where can I get such a part number index? Until now the names of the HP IC's are a secret for me.


I traveled to the museum and made the ROM based keyboard test (mode 13 at CPU card).
Self test progress goes then until "7P".
No reaction when pressing any keys at keyboard and soft keys at screen.
I've disconnected main keyboard then and pressed soft keys at the screen again. Also no reaction.
So I suspect the keyboard controller is defective, not the keyboard.


Paul Berger
 

The best cross reference I know of is the one offered by Sphere https://sphere.bc.ca/download/hp_xref-free.pdf

Paul.


On 2022-04-30 06:14, OldHP wrote:
On Tue, Apr 26, 2022 at 04:45 PM, Rik Bos wrote:

With use of the hp part number index you can see what the manufacturing number of the IC is.

Where can I get such a part number index? Until now the names of the HP IC's are a secret for me.


I traveled to the museum and made the ROM based keyboard test (mode 13 at CPU card).
Self test progress goes then until "7P".
No reaction when pressing any keys at keyboard and soft keys at screen.
I've disconnected main keyboard then and pressed soft keys at the screen again. Also no reaction.
So I suspect the keyboard controller is defective, not the keyboard.


OldHP
 

We made first measures an the keyboard port: all wires erroneously have static levels. :-(
Next step will be to check the two PHI signals beginning at 1820-1849 IC at the keyboard logic card (45000-66508).

I'm astonished the boards of the HP250 have metric dimensions.
Does it mean the computer was developed in continental Europe?
Some of my boards have stickers "Made in Germany", but with HP logo.


Steve Leibson
 

The HP Museum has a nice write up about the HP250's history:

http://hpmuseum.net/display_item.php?hw=249

The short version: The HP 250 was developed in Fort Collins, Colorado by the Fort Collins Systems Division (what used to be the Desktop Computer Division) and then transferred to the General Systems Division. The HP 250 was based on the same Hybrid Microprocessor used for the HP 9825/31/35/45. Boeblingen Division made HP 250s for the European market.

--Steve


On 5/8/2022 8:58 AM, OldHP wrote:
We made first measures an the keyboard port: all wires erroneously have static levels. :-(
Next step will be to check the two PHI signals beginning at 1820-1849 IC at the keyboard logic card (45000-66508).

I'm astonished the boards of the HP250 have metric dimensions.
Does it mean the computer was developed in continental Europe?
Some of my boards have stickers "Made in Germany", but with HP logo.
-- 
Steve Leibson

Phone (Cell): 408-910-5992
Phone (Home): 408-292-4930


Please feel free to link to me on LinkedIn


History site: www.hp9825.com