[Geoman]

They guy wrote: "With big SGI Monitor, Keyboard, Mouse, CD-Rom und booting IRIX 5.3" -- so I bought that thing at once. It's even near me so I can pick up locally.

Context: Split off a What's on eBay Thread: https://forums.irixnet.org/thread-2763.html

[jan-jaap]

Nice! Looks like you'll need to extract it from an attic. Keep us updated

[Geoman]

Thank you for your answers   that helped a lot! 

[jan-jaap]

You cannot simply replace the CPU with a 150MHz one, you also need to replace a 50MHz oscillator with a 75MHz one and replace a PAL somewhere.

The memory is PowerSeries specific, and comes in 2 or 8MB (red stripe) sticks. Most Crimsons came with 64MB RAM 'from the factory' but it wasn't Kingstom memory.

[GeekLucanis]

I was talking to Ian, and if you install a 150mhz cpu and replace the 50mhz oscillator to a 66mhz oscillator without updating the rom, you'll get a 133mhz machine, apparently.

link providing more context:http://www.sgidepot.co.uk/simonpigot/r4400/r4400board.html

[Geoman]

You cannot simply replace the CPU with a 150MHz one, you also need to replace a 50MHz oscillator with a 75MHz one and replace a PAL somewhere.

The memory is PowerSeries specific, and comes in 2 or 8MB (red stripe) sticks. Most Crimsons came with 64MB RAM 'from the factory' but it wasn't Kingstom memory.

I was talking to Ian, and if you install a 150mhz cpu and replace the 50mhz oscillator to a 66mhz oscillator without updating the rom, you'll get a 133mhz machine, apparently.

link providing more context:http://www.sgidepot.co.uk/simonpigot/r4400/r4400board.html

I was interested if changing the CPU was a simple task. But I will refrain from modding this machine in any way, because I think it's an historic piece of art and will leave it as it is. Only the leaked/bulged capacitors have to to, since they are a risk for the machine due to the acid.

Concerning the memory, I find it remarkable that there were Kingson ones inside. I guess there must have been a memory failure of the original SIMMs. Otherwise one would have simply added the Kingston-Modules afterwards while keeping the original modules.

While I have to say these boards full of custom ICs are a sight to behold, they will be a diagnostic nightmare if one ever fails... then only a capacitiy like Ken Shirriff https://www.righto.com/p/about-ken-shirriff.html (known from the Alto and AGC restaurations) can reapir that thing. While handling the electronics of the machine I always had an ESD-strap on my wrist.

[Geoman]

As I tested a custom null modem cable, the situation described by Jan-Jaap on Nekochan June 17, 2004 occurred, see  First power up, Crimson and PowerSeries - Page 1

Next up do a test run with the cards installed and monitor the LEDs on the cards. If they are "solid" (there is supposed to be LED activity during operation): good. If they all blink "nervously" in sync: power down immediately because you've got a PSU problem. Do not run the system for too long with the card cage open.

The LEDs from the mainboard blinked and the machine powered up and down. And despite its looking undamaged, it is an Cherokee-PSU. So I guess this will be a greater reastauration project as I initially thought:
1. Solder Keyboard-Adapter
2. Replace broken caps
3. Find a PowerOne PSU


Edit: Wow this forum is excellent!

https://forums.irixnet.org/thread-427.html

all the research is there - thank you guys!

[Geoman]

Okay here is the problem: CB_HK & especially jan-jaap did an excellent job in researching the PowerOne-PSU. The thing is, my Crimson has a Cherokee. So I cannot simply buy a generic SPM5ADAELBS180 and do a replacement, because those are missing the "AE board (5/12 volt)" ["Also, the SGI (S180) version includes an extra PCB which effectively sites between the control input and the backplane. You've got to keep that, of course."]

So I have got 2 choices: Try to repair the Cherokee or buy an SGI 041-0001-001.

Then there are these giant blue voltage rails, Cherokee and PowerOne each have their own.

So at the moment there is a white, errm crimson red elephant standing in my living room.

[Geoman]

In the otherwise well crafted PSU I found a charred PCB, that has end-stage carbonized and therefore conducting characteristics. 

That was the sweet-burned smell while testing the Crimson at the seller's. Like a sweet cigarillo. 

I see a double-sided PCB, I wonder if I manage to reddesign it and order a replacement via "pcbway". I fear there might be some rare components on it...

[weblacky]

While I've never been inside these PSUs, I've been inside a few SGI workstation PSUs. Yes many are customized, but take heart in the that they aren't designed by SGI, they were all designed by power supply companies of the day. That often means, off the shelf parts. So I'd be very hard pressed to believe those parts are wholly-proprietary to SGI (weren't not talking Apple Computer here). Yes, the ICs will be discontinued and may not have modern-day formfactor replacements, yeah the connectors are also the same (but you'd often reuse those), but the power circuitry, I'd bet fair money you can find modern replacements for those parts.

You just have to be very meticulous in your desoldering, recording, documenting. But unless you find a custom management IC that has burnt out, I'd guess you'll do fine given time and care.