[jan-jaap]

The Crimson will almost certainly need a PSU rebuild. I think most Crimsons came with a Cherokee (black) PSU but they work with a PowerOne PSU (silver) usually found in the PowerSeries as well.

I just finished rebuilding the PowerOne PSUs of my 4D/380VGX, 4D/440VGX and Crimson RE systems. The filter caps of the output modules were completely shot, leaking goo everywhere. To inspect them you need to basically take the whole thing apart so  you might as well replace them while you're in there. I rebuilt at least 5 of these so I know their weak spots. Here's some more detail.

If you've got a Cherokee PSU in there, well, good luck. If these things go, they go with a bang and you're left with scorched PCBs that are basically trash. It's also not modular so much harder to work on.

You'll want to be very careful around the RealityEngine, especially the RM4 board(s). They take considerable force to push into the backplane, but are thinner than what the guide rails of the card cage are made for so they can flex and wobble when you push them in. That, with a board full of large QFP chips and brittle 30 year old soldering joints is a big risk. Consider leaving the RE in place if you can. But check that all fans underneath the fan cage work (they are not monitored).

The Onyx and Challenge have their own gremlins. I never looked inside an OLS (yet) but didn't have one fail on me either so far. The most common power failure seems to be coming from the VCAM: -5 and -12V out of spec, system shutdown. Last time that happened to me it wasn't even coming from the VCAM itself, but from the monitoring circuit in the system controller.

All of these systems are going to have dead RTC batteries. In the Crimson that means garbled environment variables and it doesn't know 'resetenv'. But at least it keeps it's system serial#. The Challenge / Onyx have two Dallas chips each, one of the system controller and one on the IO4.

The Challenge is probably the least involved to get going. Pull everything except the IO4, the system controller and the 512 power brick. Hope the OLS works and see if all voltages come online good on the LCD. From there, add back a CPU board and the MC3 (you will probably need to pull all SIMMs and clean contact edges first) and see if she will POST. Then put everything else back in. In case of power problems, refer to the "Challenge/Onyx Diagnostics Roadmap" document which you can find on Ian Mapleson's site.

Invest in some good equipment. A decent soldering station with a couple of tips gives better results and saves frustration. You'll need an oscilloscope with an isolated probe if you want to measure anything in the interesting (not galvanically isolated!) parts of a PSU.

Good luck, and be careful!

NB: A Crimson RE is a pretty rare and valuable systems these days, so you want to take your time with it and not rush things. Or, depending on your skills, simply sell it as-is to someone who knows what they're doing rather than breaking it.