Siemens Nixdorf PCD-3Bsx not POSTing \ VOGONS

Siemens Nixdorf PCD-3Bsx not POSTing

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First post, by Tomek TRV

Posted on 2023-08-17, 21:00

Tomek TRV Offline

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Hi
I am working on PCD-3Bsx which is not starting. I have diagnostic card and I see that I have all voltages (I tried 2 power supply), POST code is "----" and CLK, FRAME led are on but maybe not so bright like voltages LEDs. I don't see any flash of RESET LED. Maybe I am wrong but I think that it should flash after turning on.

There is no electrolitic capacitors on this board and I also checked it for shorts on power supply connector. Mainboard (actually main card) looks perfect - no battery leakage, no damage (beside SIMM slots).

I don't know what should be connected to some pin headers: X4 NMI; X10; X11 and I have two connectors which I don't know where to connect: ST3 (two wires) and ST4 (one wire). PCD-3Bsx don't have reset buton so I think that one of these connectors can be for this function. Maybe somebody have the same computer and can help me with this.

30 pin SIMM sockets are in bad condition because they are plastic and as we know it is easy to damage clips. My SIMM sockets for bank 0 and bank 1 are an example of this problem. I know that 386SX needs two simm's in bank (because they are 8 bit each) but the question is: can I install SIMM modules to bank 3 and 4 leaving bank 0 and 1 empty?

This computer look's great and I hope that somebody will help me to bring it back to life.

Reply 1 of 5, by Tomek TRV

Posted on 2023-08-19, 19:02

Tomek TRV Offline

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SUCCESS
Nobody answer but I will write here what I learned. Maybe someday it will be useful for somebody. So:
1. Connectors ST3 and ST4 must be connected to X10. Without this connection computer will not post. I still don't know what is X4 NMI and X11.
2. Computer will not run with memory in bank 3 and 4 . Memory modules must be in bank 0 and 1 so now I have to desolder these sockets and solder good ones into bank 0 and 1.
Now it is time to wash the case and build nice 386SX.

Reply 2 of 5, by HanSolo

Posted on 2023-08-20, 09:37

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That's a cute little PC 😀 Didn't know it exists

Reply 3 of 5, by CoffeeOne

Posted on 2023-08-20, 09:42

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Tomek TRV wrote on 2023-08-19, 19:02:

SUCCESS
Nobody answer but
.....

Pictures would have been helpful to catch the attention of readers.

Nevertheless, good job.

Reply 4 of 5, by GeorgeMan

Posted on 2023-08-20, 09:49

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Tomek TRV wrote on 2023-08-19, 19:02:
SUCCESS Nobody answer but I will write here what I learned. Maybe someday it will be useful for somebody. So: 1. Connectors ST3 […]
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SUCCESS
Nobody answer but I will write here what I learned. Maybe someday it will be useful for somebody. So:
1. Connectors ST3 and ST4 must be connected to X10. Without this connection computer will not post. I still don't know what is X4 NMI and X11.
2. Computer will not run with memory in bank 3 and 4 . Memory modules must be in bank 0 and 1 so now I have to desolder these sockets and solder good ones into bank 0 and 1.
Now it is time to wash the case and build nice 386SX.

Hi!
I have exactly the same computer. It was working good, stored in my wardrobe for many years but when I saw your post I took it out to see what's connected where inside the case to help you.
I then realised that it's not working anymore. I measured the psu rails with a multimeter, they seem fine. I reseated the wdc vga card and the memory, but still no signs of life. I don't know what else to check. I had removed the nicd battery years ago, I remember it posting without the battery connected.
The hdd spins up fine so the psu should be ok, but nevertheless I tried unplugging the ide and floppy cables but no luck. CPU gets warm. My memory slots are not broken.

Reply 5 of 5, by Tomek TRV

Posted on 2023-08-20, 21:19

Tomek TRV Offline

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Rank: Newbie
Posts: 53
Joined: 2022-12-19, 13:19

It would be good to have diagnostic card. Then You could see is there any activity. At Your place I would disconect everything what is possible, all connectors but also pull out BIOS chips and assembly everything again. After so long time there may be some oxidation and, like in my case, take care about ST3 and ST4 connectors. Also it would be good to try with other simms. There is not much things that could damage on this motherboard, no electrolitic caps, no Varta (my Maxel is dead but not leaking). I hope You will bring it back to life.

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