[weblacky]

Did you measure the actual voltage it complains about?

I'm facing a similar problem in my Challenge L deskside which was complaining about the -5 and -12 being out of spec. I measured them and they were fine, it was the monitoring circuit that was broken. Borrowed the system controller from my Onyx IR and all was good, installed a spare system controller and (1) that one complained that all voltages were 10% too low, but (2) the 5V supply which feeds the MCU on the system controller (which has 8 A/D channels used for measuring voltages and the blower) was 10% too high @ 5V6.

I'm now waiting for parts to rebuild the 5V supply on this system controller.

In this case the answer is, no...I did not actually measure them...but that's because the DS1780 onboard the PIMM is what is reporting that for me (also tiny traces, live voltages...shaky hands...slipping...not a good plan). Everything comes through the MegArray and as you know...you don't mess with a MegArray!  So there are no obvious "tracks" for each voltage...I've just been guessing based on layout.  But as I mentioned, a lot of the PIMM rails show shorts in diode mode with 25 Ohms or less of resistance in Ohm mode.  They still pull current..but aren't a dead shorts.

It's very likely that there is a short BEHIND a ~25 Ohm resistance..so it pulls but the 25 Ohm resistance limits how much and saves the other regions. which also limits the severity of the voltage drop.

I truly believe it's accurate (at this time), however I am going to try to track down the 12V line by backtracking the 12V DS1780 sensor line on the PIMM.

Now when the DS1780 says the 12V rail is low...it doesn't mean the ENTIRE machine's 12V rail is low, only locally.

You see, if the V10 design is any indicator, the SGI designers loved using resistors and resistor arrays to current limit both sensors and various regions.  So we're often talking about a local voltage drop due to a local short.  Also these resistors compartmentalize the damage the short causes.

Also while it may be first-come-first-serve on the ATTN warnings, it's my impression (from at least a shorted V10 I had) that ALL errors are reported so I assume the PIMM 5V error was cured by the work I did, the fact that that larger feed 12V rail is also pulling down doesn't prevent the 5V PIMM line from working on standby as ~9V can still produce 5V via buck converter.

So this seems like a good and simple progress on finding multiple shorts.  But for now I'm trusting the DS1780 to do its job and let me know what's going on.

I know older machines don't have this luxury but with the knowledge of the DS1780 ICs exitance in this later platforms, we KNOW how voltages are reported and a general knowledge of which one reports what (only for PIMM and XIO at this time).  But, you make a good point...checking the protection around the PIMM DS1780 will also reveal the voltage tracks AND some if any of the protection resistors are out of tolerance that causing false errors.