Might be a longshot, but you if you cut off the connector that goes to the motherboard, you might be able to splice a homemade power supply adapter. It's what I did for my NCR System 3200 386 machine after I blew up two power supplies.

I wouldn't dare. Sometimes these systems have some jackass way of starting the power supply.

At least not without more research.

I've been working on reverse engineering the PSU already. I've got some info figured out and I'm working at trying to make an external setup to trip the PSU on. Not only does that make fixing the PSU easier, it'll help to figure out if I can rig something else up.

Kind of like lucky Bob said, this thing is pretty screwed up. It's more ATX like in that it has 5v standby power and isn't just mains switching.

Unfortunately so far it's all being done with a multimeter and notes as no one has the service manual.

There is something to be said to repair the damage and keep it as close to original as possible.

Repair the traces, replace the mosfets and caps. The choke will probably still work, if the insulation is still intact. Worst case, you can get some wire of equal gauge and re-wind it.

I assume you already tried bridging the broken traces on the PCB and replacing the larger caps? How did the symptoms change?

So, it's been a while but, guess what's up and running. Here's a quick video of the first power on of it. https://www.youtube.com/watch?v=y0ZZMGsougw

It's a lot more complex than I thought. It seems to have its own onboard firmware setup that can run diags and all that. Pretty ahead of its time, especially for an x86 box.

Have you been told it's likely the CMOS battery is dead, yet? 🤣

Looks really interesting. Also, hard to understand without a manual.

Are all those diagnostic tests are being run from a firmware EPROM chip? Does it run them every boot?

How far are you from installing DOS and running DOOM? And how from from a CPU upgrade? It would be really exciting to get some faster CPUs, more RAM, and more cache in there, if they aren't already maxed out.

I've got a dual Pentium 90 CPU card and fully loaded RAM card (128MB or 256MB, not sure) somewhere... It's all I saved from the ones I found with a missing power supply.

Looking forward to this getting back up and running properly.

Yes diagnostics, no not too close to getting anything installed yet. It's failing the processor board during the self test unfortunately, but it does provide some useful information.

I need to figure out which way the interconnect numbers pins and trace back from there to find out what's failing. Unfortunately Pin 1 isn't marked anywhere so I suppose there's a 25% chance of figuring it out right away. Either way, I've got a 'scope here.

This thing is very un-PC like in that the diagnostics are running on a separate CPU and separate ram from the main system. You can pull the ram and CPU boards and it'll error that they're not there but still drop you into the diag menus. Some other cool features are stuff like built in ram tests, cache tests and power supply voltage monitoring.

yawetaG wrote:

Looks really interesting. Also, hard to understand without a manual.

If anyone has one, it's NCR P/N D2-0524-A. It looks to be unobtanium though.

Sent you these on IRC but figured they'd be helpful here for reference.

Press release PDF http://www.thecorememory.com/3000_Press_Release_1990.pdf

for a 3445 but might be of use http://www.thecorememory.com/NCR_3445.pdf

https://web.archive.org/web/20000605134203/ht … ystems/3450.htm

https://web.archive.org/web/19970617153011/ht … t/nt/ipdocs.htm

http://www.thecorememory.com/Aberdeen3000report.pdf

this site has lots of info on NCR http://www.thecorememory.com/index.html

Really a very nice box. Once owned a NCR 3434 myself, but passed it to another microchannel collector. Still own the dead PSU as I was able to obtain a working one from a collector in the netherlands. Need to check my archives if I might have some docs on this one from the late 90s when there were still downloads availiable at NCR. Did you ask in the comp.sys.ibm.ps2.hardware computer newsgroup? Despite the name, all kind of microchannel machines are dealt with there and some people there have excellent knowledge on these systems.

Pics of the Pentium 90 CPU card and RAM card - https://imgur.com/a/f86WUPN.

These came out of a 3450 that appeared to have been upgraded several times in its life. It had 2 of these single CPU cards (the other big chip under the heatsink is a cache controller, not a 2nd CPU). Looking at the PCB layout it looks like dual CPU cards were also available. The dual CPU cards appear to have the RAM on the CPU card and use 72 pin SIMMs. The custom PANTHER3 bus chip is bigger than the Pentium CPU.

The RAM card has 48 64 pin SIMMs slots. Each SIMM has 14 chips on it (ECC?). This card is older than the CPU cards possibly from the original 486 configuration.

That system is absolutely a beautiful beast. I really hope you can fix what ever is wrong and get it back to a fully running system.

Update quite a few months later: It works! Sort of. I decided to dig it out again today and see if it magically fixed itself, and sadly it did not. I did find a way to make it work though.

Here's a pic of the system actually accepting everything installed:

How much ram does it have? 64 megs.

Oh yeah, and I picked up a 2nd MCA based NCR 486. This one's an NCR System 3434, a single 486 CPU but still MCA based. Not as cool as the 3450, but shoot, it's still a giant MCA based non-IBM box.

Oh my.

Are you going to see if Windows NT 3.51 or NT 4.0 will install? Might be neat to run WinQuake for kicks. I assume there weren't any 3D accelerators for use on this platform.

This is pre APIC (1992 82489DX) so needs very custom OS support to work. It probably wont even run non vendor specific NT install.