SGI O2 stuck at boot with Amber LED

[SGIArtist]

Because my new O2 was quite loud, I decided to replace the PSU and CPU fans. After replacing the PSU fan the machine worked without a problem. Then I replaced the (R10K) CPU fan for a noctua NF-A6 PWM. After pushing the system board back into the machine it's now stuck at boot with an amber led. I have to unplug the machine to shut it down and when I plug the power cord in it immediately starts the machine up. Pushing the reset button, the led turns red briefly, then becomes amber again. According to the reference manual flow chart it's a system board problem.

Things I already tried:
- I popped the RAM and pushed it back in. Tried only first two slots with different DIMMs
- Re-seated the CPU twice
- Reinstalled the old fan
- Power on jumper trick (three times)

Output to the serial port gives nothing, except when pressing reset button the output is "[00]".

Is there anything else I can try? I did unplug the power cable every time I removed the system board or put it back in.

 

[kikems]

My O2 in the mainboard have a 2 pins for a jumper , use a jumper to connect pins during few seconds and later remove jumper. This works for me for hard reset mainboard and Prom values.

Usually an amber light is a recoverable machine. Remember connect mouse and keyboard before power on, sometime you have amber light because not keyboard connected or keyboard fairule.

 

[SGIArtist]

Thanks. Tried both multiple times. Unfortunately no change.

Edit: I've tried loading the system board without any ram, which gives me a blinking amber red. So at least something different. I'll try some different RAM combos.

Edit2: tried multiple RAM stick combinations in first two slots, with no result.
Edit3: tried booting without the PCI slot addon, got an amber LED as well.

 

[kikems]

In this case maybe you have a problem with the CPU board. I you have another R5k O2 you can change CPU board easy to test.

 

[SGIArtist]

I think you're right. Without additional hardware there's not much I can do. Guess I'll have to go searching. Thanks.

 

[Jacques]

If you have an R5k CPU you can test it to see if it's the CPU or the system board. I sold a second spare 180Mhz R5k cpu last year for £5, pity as I would happily have sent it to you for postage.

 

[SGIArtist]

Thanks man. I'm pretty sure it's the CPU that's the problem.

 

[SGIArtist]

I got a new CPU board from a local seller. That seems to have fixed the issue. Somehow I damaged the original board when screwing in the new fan. Thanks for all the advice and help.

 

[Jacques]

Result! Well done.