Did you try it without the case? I had a similar problem (DIN keyboard with adapter). It turned out the adapter was slightly short and was blocked by the case

I tried using an IBM PS/2 model 25 with a Microsoft Natural Ergonomic wired (beige) keyboard, purchased in 2000. They didn't jive.

Try another keyboatd (apologies, I didn't read your whole post).

Here my theory:
In the technical documentation it seems like in the drawing the keyboard connecor is AT.
Some of my PS2 keyboards work on AT machines with a ps2>at adapter, some dont...

Maybe you need a PS2 Keybaord that can "still talk AT" (or a AT keyboard with a AT>PS2 adapter).

Check the inductors around the ps/2 keyboard connector for continuity.

Zerthimon wrote on 2023-09-21, 21:03:

Check the inductors around the ps/2 keyboard connector for continuity.

Yeah I did that. Also checked the diodes. For the Caps I don't know their values but my multimeter shows that they all charge up.

HanSolo wrote on 2023-09-21, 20:23:

Did you try it without the case? I had a similar problem (DIN keyboard with adapter). It turned out the adapter was slightly short and was blocked by the case

kant explain wrote on 2023-09-21, 20:25:

I tried using an IBM PS/2 model 25 with a Microsoft Natural Ergonomic wired (beige) keyboard, purchased in 2000. They didn't jive.

Try another keyboatd (apologies, I didn't read your whole post).

DerBaum wrote on 2023-09-21, 20:48:

Here my theory: In the technical documentation it seems like in the drawing the keyboard connecor is AT. Some of my PS2 keyboard […]
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Here my theory:
In the technical documentation it seems like in the drawing the keyboard connecor is AT.
Some of my PS2 keyboards work on AT machines with a ps2>at adapter, some don't..

Maybe you need a PS2 Keybaord that can "still talk AT" (or a AT keyboard with a AT>PS2 adapter).

I will take the thing apart today again and check for shorts. I was going to put the board into another SNI case I have lying around anyway. Also the eBayer answered and she was using some old HP Keyboard. Might be the reason it worked for her because as you (Herr Baum 😉 ) already said...that AT connector and no further info on that in the handbook kinda tripped me up as well. I ordered a new keyboard from Amazon (which I don't think will work but I'd like to try) and I found an old SNI ps/2 keyboard from the 90s for relatively cheap. Let's see if that works. Initially I wanted to see if I can just put together two at->ps/2 - ps/2 -> at adapters just for the kicks. Maybe I still have an AT to ps/2 one in one of my unordered boxes.

DerBaum wrote on 2023-09-21, 20:48:

In the technical documentation it seems like in the drawing the keyboard connecor is AT.

The image is not precise anyway. Mine has a 128k cache pre-soldered to the board already with 4 slots + tag slot for another 128k and there is no Bank1 for vram. Maybe they started this D756-type board with an AT connector and replaced it with a PS/2 connector later. The early 1992 version of this board that I had back then came with PS/2 already as well. So they must have made the change early on. Also my board features a CL-GD5428 VLB graphics chip and not a 5426. Looking at the chips (4xHYB514256B-60, 4xHYB514256BJ-60) it seems to have 2MB vram as well which is a lot! They definitely innovated on this board.
I also have a hard time finding any sticker or serial that indicates from when this board here is specifically. Maybe when I get into the BIOS the reset clock gives an indication but I suspect it to be a late '93 version

afaik signaling and protocol is same for both AT and PS/2 keyboards.

rasz_pl wrote on 2023-09-22, 11:35:

afaik signaling and protocol is same for both AT and PS/2 keyboards.

Indeed. The adaptors are purely passive pin-to-pin connections and specifications are identical. It's XT keyboards that talk a different protocol.

What can differ is power draw. Some keyboards (IBM monsters...) draw a lot more than others (eg. Cherry, Alps or Rubber dome), leading to issues, either permanent (won't work) or intermittent (sometimes keypresses not registering, some boots keyboard error etc). I've had that with a KVM switch that wouldn't work reliably with a 2nd gen Modem M IBM Enhanced Keyboard. Worked fine with pretty much anything else I hooked up.

Given the small form factor here that might also play a role, but first things first I'd get the board out of the case and see if something's not shorting - not to mention trying with a few other keyboards.

dionb wrote on 2023-09-22, 12:53:

Indeed. The adaptors are purely passive pin-to-pin connections and specifications are identical. It's XT keyboards that talk a d […]
Show full quote

rasz_pl wrote on 2023-09-22, 11:35:

afaik signaling and protocol is same for both AT and PS/2 keyboards.

Indeed. The adaptors are purely passive pin-to-pin connections and specifications are identical. It's XT keyboards that talk a different protocol.

What can differ is power draw. Some keyboards (IBM monsters...) draw a lot more than others (eg. Cherry, Alps or Rubber dome), leading to issues, either permanent (won't work) or intermittent (sometimes keypresses not registering, some boots keyboard error etc). I've had that with a KVM switch that wouldn't work reliably with a 2nd gen Modem M IBM Enhanced Keyboard. Worked fine with pretty much anything else I hooked up.

Given the small form factor here that might also play a role, but first things first I'd get the board out of the case and see if something's not shorting - not to mention trying with a few other keyboards.

I second that. The old IBM monsters are much more power hungry. By today standards.
They worked within the specs of the old IBM PCs and ATs, after all.

Another issue that comes to mind is a keyboard lock.
Some PC chassis have a lock feature that "cuts" the keyboard power or keyboard i/o.
Not sure if it's true for this particular PC model, though. 🤷‍♂️

Jo22 wrote on 2023-09-22, 13:20:

Some PC chassis have a lock feature that "cuts" the keyboard power or keyboard i/o.

marbury wrote on 2023-09-21, 20:14:

The Keyboard lights up when I plug it in. So it seems to have power.

^

Jo22 wrote on 2023-09-22, 13:20:

Not sure if it's true for this particular PC model, though. 🤷‍♂️

Edit: I think it would be helpful if there's a manual available somewhere.
Such computers were quite odd at times.

Edit: There is. The technical manual is available on the site linked in first posting.
It says as follows:

"Security Features
This field allows you to define a password to prevent access to the data in
your PC. The following options are available:
DISABLED
No passwords are in effect.
SYSTEM AND Setup LOCK
The SETUP menu and operating system are protected by passwords.
Setup LOCK
The SETUP menu is protected by a password.
KEYBOARD AND Setup LOCK
The SETUP menu is protected and the keyboard and the mouse are
locked by passwords.
CHANGE PASSWORD
This option is displayed only if a password has already been defined. It
enables you to alter the password.
Default entry: DISABLE "

Jo22 wrote on 2023-09-22, 15:34:

Edit: There is. The technical manual is available on the site linked in first posting.
It says as follows:

Yeah but that could not have been it for 2 reasons:
- completely wiped the cmos multiple time
- setting a password shouldn't give a "NO KEYBOARD" error but present a field to enter a password. Not making it possible to use you keyboard ever again would make that a setting to effectively brick you computer for good 😉

But to answer this question. Except for the BIOS password there is no intrusion prevention on the board.

But anyway girls and guys. I spent the last two hours or so debugging this. I measured everything my multimeter could measure in the vicinity of the ps/2 ports again and again. Everything capacitates, resists and diodes as is should. I also took a piece of wire put it in each of the ps/2 holes and tried to find a matching pin on U41 for the 4 connected ps/2 pins. Which worked. While doing that I noticed that the data-pin of the ps/2 connector seemed to be worn out a bit making the wire wobble around a bit more in that hole.

I think a change of the port is in order at some point. But I don't have a ps/2-port at home at the moment and first need to order one.

So desperate times call for desperate measures. I took a DIN-port and whipped up this contraption to test with thicker wires.

Guess what ... it works. omg!

marbury wrote on 2023-09-22, 16:02:

Yeah but that could not have been it for 2 reasons: - completely wiped the cmos multiple time - setting a password shouldn't g […]
Show full quote

Jo22 wrote on 2023-09-22, 15:34:

Edit: There is. The technical manual is available on the site linked in first posting.
It says as follows:

Yeah but that could not have been it for 2 reasons:
- completely wiped the cmos multiple time
- setting a password shouldn't give a "NO KEYBOARD" error but present a field to enter a password. Not making it possible to use you keyboard ever again would make that a setting to effectively brick you computer for good 😉

But to answer this question. Except for the BIOS password there is no intrusion prevention on the board.

Hi there! There's a misunderstanding, I'm afraid. 😅
I didn't even try to prove my idea here. I was only looking for an answer for the problem.
The quote was just meant as a help to clarify the situation, not to express that I'm right.

The quote from the manual essentially talks about keyboard protection being a software solution, rather than a hardware solution.

Anyway, I'm really glad that it now works.
Siemens PCs aren't exactly "0815" (generic), so to say. Sometimes the company comes up with unusual solutions. 🙂

Jo22 wrote on 2023-09-22, 16:20:

Hi there! There's a misunderstanding, I'm afraid. 😅 I didn't even try to prove my idea here. I was only looking for an answer fo […]
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Hi there! There's a misunderstanding, I'm afraid. 😅
I didn't even try to prove my idea here. I was only looking for an answer for the problem.
The quote was just meant as a help to clarify the situation, not to express that I'm right.

The quote from the manual essentially talks about keyboard protection being a software solution, rather than a hardware solution.

hehe, was wondering why it would be useful to brick a pc by design 😁

Jo22 wrote on 2023-09-22, 16:20:

Anyway, I'm really glad that it now works.

Yeah but now I need a PS/2 socket and stupid Munich, Germany does not have any electronics store left where I can buy one socket for 50ct without paying 6bucks for shipping m(
Or is anyone here from Munich and we can meet in an hour exchanging a PS/2 socket for some money....?

marbury wrote on 2023-09-22, 16:33:

Yeah but now I need a PS/2 socket and stupid Munich, Germany does not have any electronics store left where I can buy one socket for 50ct without paying 6bucks for shipping

Hm. All that comes to mind is Conrad Electronic. It had a big outlet there, if not the most important one, but that was in the 90s.
It's probably closed by now. 🙁

Jo22 wrote on 2023-09-22, 16:54:

marbury wrote on 2023-09-22, 16:33:

Yeah but now I need a PS/2 socket and stupid Munich, Germany does not have any electronics store left where I can buy one socket for 50ct without paying 6bucks for shipping

Hm. All that comes to mind is Conrad Electronic. It had a big outlet there, if not the most important one, but that was in the 90s.
It's probably closed by now. 🙁

yeah, they closed almost all Conrad stores in all of Germany. Munich had two. Both closed for years now 🙁 ... and in their online shop they don't have even a "ps/2 Einbaubuchse".

marbury wrote on 2023-09-22, 17:32:

Jo22 wrote on 2023-09-22, 16:54:

marbury wrote on 2023-09-22, 16:33:

Yeah but now I need a PS/2 socket and stupid Munich, Germany does not have any electronics store left where I can buy one socket for 50ct without paying 6bucks for shipping

Hm. All that comes to mind is Conrad Electronic. It had a big outlet there, if not the most important one, but that was in the 90s.
It's probably closed by now. 🙁

yeah, they closed almost all Conrad stores in all of Germany. Munich had two. Both closed for years now 🙁 ... and in their online shop they don't have even a "ps/2 Einbaubuchse".

I just had to verify this
searched conrad.de for this "mini din"
and this was in the list
https://www.conrad.de/de/p/mini-din-einbaubuc … -st-741797.html

there was also a green one. didn't check if there was a plain black one before replying 😀
edit: just noticed the category that connector is listed under... "centronics" *sigh* 😐

weedeewee wrote on 2023-09-22, 17:43:

I just had to verify this searched conrad.de for this "mini din" and this was in the list https://www.conrad.de/de/p/mini-din-ei […]
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I just had to verify this
searched conrad.de for this "mini din"
and this was in the list
https://www.conrad.de/de/p/mini-din-einbaubuc … -st-741797.html

there was also a green one. didn't check if there was a plain black one before replying 😀

Interesting, thanks for the tip! 😎👍
The term "mini din" is surely correct, but not exactly what's being used in daily life.
So that's why it didn't cross our mind, maybe.

Another, one for the DIN connector, is "Diodenstecker" (diode plug).
The same one that MIDI uses, I think.
It's a lesser known term, I believe.
Edit: I must correct myself. The 3-pin model is a Diodenstecker.
The 5-pin model must be explicitly named as such ("5 poliger Diodenstecker"). 😅

Btw, there are still three Conrad "shops" open, it seems. Hm. That's unexpected.
One of the three is a bigger store in Regensburg. It's for business customers, though, it seems.

Then there's one in Mannheim, which my dad claims to remember visiting once.
It's also next to the Conrad warehouse, I assume?
It will be transformed into a store for business customers, as well, if I understand correctly.

The third one apparently is in a kaff (eng. hicksville) in Bavaria I never even heard of.
The location is some sort of market, where Conrad has its logistics central or something. 🤷‍♂️
It's the closest to Munich, maybe. But still not "close" in the usual sense.

So it's not really something for private people to casually visit, not a Radio Shack like experience.
Private and business customers of Conrad have different customer numbers, also, if I remember correctly.

weedeewee wrote on 2023-09-22, 17:43:

I just had to verify this
searched conrad.de for this "mini din"

Yeah, you're right. I always neglect that this is "mini din" *sigh*

Jo22 wrote on 2023-09-22, 18:08:

Btw, there are still three Conrad "shops" open, it seems. Hm.

yeah I know. They are ... as you said already ... somewhere nobody wants to go to ;o) And the one in R is not open to the public.