Hello Willis, I don't have a photo of my Tower AT's PSU at hand, but these links might be interesting for you maybe..

Re: My Schneider AT Towers

Help me fix my Schneider Euro XT?

Re: Fixing a Schneider 386 SX System 40

Looking for Schneider Tower AT BIOS

Thanks a lot Jo22! I really appreciate that.
These links look very helpful.
I'm looking forward to read them.
I'm going to contact you back, as soon as I have results.

Hello.

The diagram, that devius had made is really helpful.
But I have several questions.
1. What is PWR ON?
When searching for the pinout of a 20 pin ATX PSU, I could only find a PWR OK and a PS ON pin.
2. Which pin is -12v and which pin is power good?
On the diagram, these pins are marked as unknown.
3. Does the power good pin and PWR OK pin even exist on a ATX PSU?
4. Which of these pins are required, for booting this thing up?

Thanks in advance for your help

Update: I have followed what Emu10k1 did in this link: Schneider 80286 PSU?
I know, that what i'm doing is incredibly risky and honestly, I really don't want to destroy anything.
Therefore, i'm going to upload some pictures tomorrow, showing what I did, before i'm doing something stupid.

Wilius wrote on 2020-08-09, 13:06:

1. What is PWR ON?
When searching for the pinout of a 20 pin ATX PSU, I could only find a PWR OK and a PS ON pin.

PWR ON has the same intention as PS ON. It is used to turn the supply on or off. I can't tell you whether it works the same way as PS ON on an ATX supply, but you can likely measure it. PS ON on an ATX supply is open (not connected to anything) if the supply is supposed to be off and shorted to ground if the supply is supposed to be on. My guess is that PWR ON is directly controlled by a physical power swithc in the VGA AT System.

Wilius wrote on 2020-08-09, 13:06:

2. Which pin is -12v and which pin is power good?
On the diagram, these pins are marked as unknown.

If the VGA AT System has serial ports, you are very likely to find 1488/1489 family chips to create the RS232 levels from the TTL logic levels. Datasheet here: https://www.st.com/resource/en/datasheet/cd00002037.pdf. VEE (Pin 1 of the 1488) is directly connected to -12V.

Wilius wrote on 2020-08-09, 13:06:

3. Does the power good pin and PWR OK pin even exist on a ATX PSU?

"PWR OK" and "power good" is the same thing. It's pin pin 8 on the 20-pin ATX connector.

Wilius wrote on 2020-08-09, 13:06:

4. Which of these pins are required, for booting this thing up?

You need +5V and GND for sure.
If there is a "PWR OK" or "PWR GOOD" pin, you likely need that too, because it's common to keep the processor in reset until a power good signal is present.
Some boards need +12V for auxiliary stuff that is needed to boot up, but possibly it works without +12V.
PS_ON or PWR ON is only needed to turn on the supply. If you use a different way to turn on the supply, you don't need that pin.
-5V is most likely not used for anything
-12V is most likely only used for serial ports.

Wilius wrote on 2020-08-09, 15:54:

Update: I have followed what Emu10k1 did in this link: Schneider 80286 PSU?
I know, that what i'm doing is incredibly risky and honestly, I really don't want to destroy anything.
Therefore, i'm going to upload some pictures tomorrow, showing what I did, before i'm doing something stupid.

That machine is still going strong. if you need photos of the backplane or something, just let me know.

I´ve just remembered that Dersammler asked me for a back up of the bios too. I should just get to it and get it done already.

Thanks mkarcher & Emu10k1 for your amazing help. I really appreciate that a lot.

Here is a little diagram I made, showing what I did.

The green circles with the white letters are indicating, that these connectors are located on the board.
L stands for left and R stands for right.

Do you guys think, it's going to work?

And Emu10k1, it would be awesome, if you could make some photos of the backplane.

Thanks in advance! You guys rock.

Sadly my vacation is ending tomorrow. This week, I have little to no time. I'm going to contact you again next weekend, or if I can.

Mine its an AT40, and it seems that we both have the same Backplane (Matching serials).

Im reusing the housing of the old psu, you´ll have to do pretty much the same to get a mini ATX or ATX inside the machine and to get the screws aligned. I really REALLY should do something about the rust in the housing though.

As you mentioned that you wont be able to get to it this week, ill take some time this weekend to change the electrical tape and take better photos of the wiring. You could probably make a better job at this than me, as I just needed it to work as fast as posible to use measurement equipment and i never thought about using a needle to take out the pins with the cables from the AT psu from the socket to insert the ones from an ATX psu without the need of bridging, soldering, or making a botch.

Also, now that i think about it, I´m not really sure right now if the floppy drive has a standard pinout either, keep that in mind if you need to clean or replace it.

Once you get it up and working, you can use a CF card of <=256 on any CF to IDE. Or you can use just a 512~4gb one if you use Ontrack manager on a boot disk or a XT-IDE on a net card. My Schneider came paired with a Crystal MPU sound along with the SBC, once you get 3 cards inside you can forget everything you know about cable managment.

I just found out that I have to go to vocational school a little later today.
I'm using this as a oppertunity, to quickly reply to your post.
1. Thanks for the amazing pictures.
2. You mentioned, that you reused the PSU housing, to fit a ATX PSU inside.
Sadly, the original owner has disposed the original housing and PSU a long time ago.
So I suppose, that this won't be an option for me. I'm going to have to build a housing from scratch.
It's not going to be pretty, but I guess it's not about the aesthetics, but rather the functionality.
3. Good, that you mentioned the Floppy drive.
Fortunately, I own the original 3 1⁄2-inch floppy drive and it indeed has a custom connector. (It say Sony MODEL MP-F17W-58S on the bottom)
In which direction is the notch of the FDD connector supposed to be facing, if I want to connect it to the backplane? (If the ISA slots are facing downwards and the I/O is on the left)
4. I'm worried, wheter there are even more custom connectors inside this thing. Will a normal AT Keyboard work with this System?
5. Before using a CF card, I want to get sure, if the original MFM HDD is indeed dead. If not, I will definitely keep the original drive.
6. Do I have to consider something before connecting it to a ATX PSU?
7. I have a small PCB with two switches. I assume one of them is the reset button. But what's the purpose of the second one?
Is this a turbo switch, or perhaps even the power switch? If yes, can I start the computer without jump-starting the PSU by connecting PS_ON# with COM?
8. Have I done everything right, in the diagram, I made?

Thanks in advance for answering my questions

Wilius wrote on 2020-08-10, 04:04:

I just found out that I have to go to vocational school a little later today. I'm using this as a oppertunity, to quickly reply […]
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I just found out that I have to go to vocational school a little later today.
I'm using this as a oppertunity, to quickly reply to your post.

3. Good, that you mentioned the Floppy drive.
Fortunately, I own the original 3 1⁄2-inch floppy drive and it indeed has a custom connector. (It say Sony MODEL MP-F17W-58S on the bottom)
In which direction is the notch of the FDD connector supposed to be facing, if I want to connect it to the backplane? (If the ISA slots are facing downwards and the I/O is on the left)
4. I'm worried, wheter there are even more custom connectors inside this thing. Will a normal AT Keyboard work with this System?
5. Before using a CF card, I want to get sure, if the original MFM HDD is indeed dead. If not, I will definitely keep the original drive.
6. Do I have to consider something before connecting it to a ATX PSU?
7. I have a small PCB with two switches. I assume one of them is the reset button. But what's the purpose of the second one?
Is this a turbo switch, or perhaps even the power switch? If yes, can I start the computer without jump-starting the PSU by connecting PS_ON# with COM?
8. Have I done everything right, in the diagram, I made?

Thanks in advance for answering my questions

3. There is no notch in the cable. Put the Blue/red stripe on pin 1, both in the motherboard and on the drive.
4. Normal AT keyboards works fine. I´ve used a generic one on this machine before (LIA KW200), the machine came paired with a Patrol K280w keyboard.
6-7. one is the reset button, the other one is the power button. i was just starting the psu that way because i was not using the power switch on the pcb at that time. you have to bridge the white AT cable to green on the ATX and red AT to Ground in ATX.

8. its mostly ok. As i said in 6-7, red is gnd and white goes to green. Look at the photos im attaching in this post. Note that you can test the psu te same way im doing it right now, just bridge white to ground after adapting your ATX psu, or bridge black and green before completely modifying it.

Before I end forgetting about it, -5v and -12 if needed seems to be done on the motherboard. The pinout was measured from the original psu on another schneider tower and no negative rail was found.

A pair of photos of the fairly ugly botch i did back then.

i´d like to say that im really happy with the uni-t multimeter im using to measure this, its not Fluke brand but its really good for ist price.

Hi there
Excuse me, that it took me so long to reply.

Once again, i want to say thank you for your precious help and support, that's very kind of you.
So far, your pictures helped me a lot.
I want to apologize for the confusion. By "notch", I actually meant cable key. (My cable has one.)
I wasn't sure, in which direction it should face, but thanks to you, I've now figured it out.
Intrestingly, my cable has only a red stripe. The blue stripe is completely missing.
I've made a new and improvised version of my diagram. It should now be fixed.
What else do I have to modify on my PSU?
Speaking of PSU, can I use any ATX power supply? What PSU have you used?

Wilius wrote on 2020-08-11, 16:29:

Hi there Excuse me, that it took me so long to reply. […]
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Hi there
Excuse me, that it took me so long to reply.

I've made a new and improvised version of my diagram. It should now be fixed.
What else do I have to modify on my PSU?
Speaking of PSU, can I use any ATX power supply? What PSU have you used?

Hey, dont worry about it.

Everything should be alright as it is. I used a Hipro of 240w from a htpc, almost any atx psu with 100w-160w+ should be enough, the HDD its probably the most power hungry thing in your setup.

Take your time, maybe check the motherboard for shorts first (continuity on 12v-ground, 5v-ground, if there is continuity then something is shorted. You can test this on the old psu too to get to know what was wrong with it and in wich rail it is). Then double check your psu setup, plug it in and lets hope you get the blessing of hearing a beep coming from the speaker. Try it with th SBC and the backplane only at first, after that add the rest of the peripherals starting with the floppy.

if the machine its still alive, youll probably need to set the values of the HDD and other things in the bios, as the dallas RTC should be completely dead.

Hi

I'm almost ready to test my System.
But before I'm going to do it, could you please tell me, in which direction the red stripe is supposed to be facing?

Wilius wrote on 2020-08-14, 15:28:

Hi

I'm almost ready to test my System.
But before I'm going to do it, could you please tell me, in which direction the red stripe is supposed to be facing?

Red stripe facing the numbers in the pcb. Exactly the way you are holding it in the photo, with the cable facing away from the pcb.

Alright

The first start didn't go so well. I have a black screen. (Who would've thought that)
At least nothing blew up.
I tested for continuity, but couldn't find any shorts.
Any advise, what I can try now?
Do you think it makes sense, to jumpstart this thing, by connecting green to ground and removing the cable of white and red?
I believe there are some loose connections on my front panel, as the led is flickering, when I touch it.
Thanks in advance.

Nevermind it just fixed itself.

Holy bleep! it's working! I simply can't believe it, but it's working. I am so happy right now, cause I thought it was dead!

Thank you guys for your amazing help. You did it. Thanks to you it's working again.
And a especially, a huge thanks to Emu10k1, for the amazing material you provided me.
You guys are the best!

Wilius wrote on 2020-08-14, 22:36:

Nevermind it just fixed itself. […]
Show full quote

Nevermind it just fixed itself.

Holy bleep! it's working! I simply can't believe it, but it's working. I am so happy right now, cause I thought it was dead!

Thank you guys for your amazing help. You did it. Thanks to you it's working again.
And a especially, a huge thanks to Emu10k1, for the amazing material you provided me.
You guys are the best!

Hey! congrats!. I'm glad I could be of help.

Enjoy!

Hello, I have sad news

I did something incredibly stupid.

I reseated the CPU board and forgot, that there was a crack in the rear of the connector.
Due to the crack, the board slided too far backwards and therefore, every pin of the CPU board were touching the wrong pins of the IO Board.
The result: I shorted the whole thing and killed/fried it.
There is visible damage, on a chip labled "Schneider BIGJIM 50773".
Is it possible to find a replacement?
I couldn't find anything about this chip online.
I assume it's probably not the only chip, which got damaged during the process.
I feel very guilty and stupid. I'm so sorry for this utter embarrasment. This is a big disgrace.
I should've paid more attention. I guess this is what you get, when you become reckless.

Despite the fact, that I already know, which chip got damaged, I still meassured for continuity.

Here is what I meassured so far:

Power Connector 1:
+12v 1909 (with CPU board installed: 1890)
+5v 806 (with CPU board installed: 096)
+5v 806 (with CPU board installed: 096)
red 873 (with CPU board installed: 873)
GND 001 (with CPU board installed: 001)
GND 001 (with CPU board installed:001)
OK_PSU nothing (with CPU board installed: 955)

Power Connector 2:
+5v 806 (with CPU board installed: 096)
+5v 806 (with CPU board installed: 096)
GND 001 (with CPU board installed: 001)
GND 001 (with CPU board installed: 001)
PWR_ON nothing (with CPU board installed: nothing)

I have also meassured the CPU Board (PDF files in the attachments)
I will also attach pictures of the faulty chip and connecter as well.

Darn, that was by far the most idiotic thing, i've ever did.
I really should've known better.

I beg your pardon

I hope someone can help me, to find that chip.
Thanks in advance for your help.