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SGI Onyx 350 Capacitor Replacement Guide

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SGI Onyx 350 power supply removal (User's Guide Figure 7-27)
Taking out an Onyx 350 compute module supply: (A) screen cover screws, (B) cover and fan swung aside, minding the ribbon cable, (C) release and green handle, (D) supply out (SGI User's Guide, Figure 7-27)

Capacitor notes for the SGI Onyx 350. SGI's user's guide treats the power supplies as sealed replaceable units and gives no component lists or capacitor values for them, for the compute module's boards or for the graphics.[1] No owner has published a capacitor list for an Onyx 350 either. The values in your system have to be read from the parts themselves; do not fit values copied from another machine.

The compute module is the SGI Origin 350's, and the owners' findings on its supplies and regulators are set out in full on SGI Origin 350 Capacitor Replacement Guide. The points below summarise them and add what is known about the graphics hardware.

Warning: the compute module supplies, the InfiniteReality module's supply and the L2 controller's supply all run from the mains, and their input capacitors can hold a dangerous charge after the cord is pulled. Unplug the module, wait, and confirm with a meter that the input capacitors have discharged before working inside a supply.

Where the power is converted

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Power conversion in an Onyx 350 system
Assembly What is documented
Compute module supplies One or two per module, each rated 500 W from 110–220 V AC. SGI's Onyx 350 guide gives the outputs as 12, 5 and 3.3 V. jan-jaap identifies the supply as a rebadged Delta DPS-500EB; jwhat's L1 reports it as DPS-500EBE, SGI part 060-0178-003.
Compute module boards The IP53 node board has VRMs for the processor core, 1.5 V and 2.5 V; the interface board has further voltage regulators.
InfiniteReality graphics module Its own supply, on the front of the midplane, from a 220 V outlet outside the rack.
InfinitePerformance module Fed by the compute module's own supplies; SGI gives about 563 W for the module.
L2 controller 48 V DC from a small supply fed by the PDU, or from a power bay.

[2][3][1][4][5][6]

What owners have found

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On the compute module, as reported on the IRIX Network forum and described in detail on the Origin 350 pages:

  • Older revisions of the Delta supply have a fault covered by Intel Technical Advisory TA-0674-5, in which the primary power factor correction diode fails. jan-jaap's own supply failed this way; he repaired it and others, and the fault did not return.[5]
  • aSpartan111 traced a missing PCI 5V rail on an Origin 350 interface board (030-1809-006, the same part as in jwhat's Onyx 350) to an LTC1629 switching regulator. New Panasonic 220 µF 6.3 V output capacitors on the PCI 5V and 3.3 V regulators did not cure it; a new LTC1629 did.[7][8]
  • weblacky, who repairs these boards, describes the regulator output capacitors of this generation as solid polymer types, and suspects ageing of their ESR in rails that drift low; he had not confirmed it.[9]

No owner reports of failed capacitors in the InfiniteReality module supply or on the InfinitePerformance board have been found.

Recording your own system

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  1. Shut IRIX down, power the system off at the L2, turn off the InfiniteReality modules' rear switches and unplug every cord.[3]
  2. Take the supplies out from the front and open the module cover as described on SGI Onyx 350 General Maintenance.
  3. Photograph both sides of every board or supply before desoldering anything, with designators readable.
  4. For each electrolytic or polymer capacitor, write down the designator, capacitance, voltage rating, temperature rating, maker and series, size and polarity.
  5. Look for domed tops, leakage at the base, brown or crystalline residue and corroded traces near capacitors.
  6. Measure ESR with the part out of circuit and compare it with the maker's figure for that series.
Record sheet
Assembly Designator Capacitance Voltage Temperature Series Size Condition
Compute module supply
2U interface board regulators
IP53 node board VRMs
InfinitePerformance board
InfiniteReality module supply

Replacing

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  • Fit the same capacitance and at least the same voltage rating, with 105 °C parts, and low-ESR series wherever the original was a low-ESR type.
  • Replace solid polymer parts with the same technology at an equal or lower ESR.
  • Keep the original size where a heat sink, duct or neighbouring part leaves no room for a larger one.
  • Mark polarity on your photographs before removing anything.

After the repair

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  1. Refit the supply without pinching the fan's ribbon cable, and leave a supply or a blanking plate in every bay.[1]
  2. Plug the module in: the supply LED should blink green, then turn steady green when the module powers up; amber means a fault.[1]
  3. Power the module up from the L2 or its L1 and run env. Every rail should be inside its warning limits; SGI counts 10% from nominal as a warning and 20% as a fault.[10]
  4. Measure the rails you worked on with a meter as well, so that a failed DS1780 monitoring chip does not mislead you.
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References

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  1. ↑ 1.0 1.1 1.2 1.3 SGI, 007-4632-001, chapter 7, pp. 136–140, Table 7-2. Power supply replacement and LED.
  2. ↑ SGI, 007-4632-001, chapter 3, pp. 54–60. IP53 node board VRMs, interface board, power supplies.
  3. ↑ 3.0 3.1 Silicon Graphics, SGI Onyx 350 Visualization System User's Guide, 007-4632-001, June 2003, chapter 2, pp. 32–45 (File:SGI Onyx 350 Visualization System User's Guide (007-4632-001).pdf). Power connections, L2 controller supply, powering off.
  4. ↑ SGI, 007-4632-001, appendix A, p. 152, Table A-5. Module input power.
  5. ↑ 5.0 5.1 jan-jaap, jwhat and vvuk, "o350 env chip locations", IRIX Network forum, 28 February to 1 March 2022, forums.irixnet.org. Supply identity, outputs and part number, TA-0674-5.
  6. ↑ Silicon Graphics, SGI Onyx 300 Graphics System User's Guide, 007-4509-002, May 2002, pp. 19 and 128 (File:SGI Onyx 300 Graphics System User's Guide (007-4509-002).pdf). InfiniteReality module power supply.
  7. ↑ aSpartan111, robespierre, jwhat, weblacky and jan-jaap, "Origin 350 - PCI 5V missing", IRIX Network forum, September to December 2023, forums.irixnet.org.
  8. ↑ jwhat, "What to do with some lonely O350's?", IRIX Network forum, 22 July 2021, forums.irixnet.org. hinv listing the 2U_INT_53 interface board, part 030-1809-006.
  9. ↑ weblacky, replies of November 2020 to March 2022 in "O350 Voltage Fault:ATTN: 1.8V low fault limit reached @ 1.396V.", IRIX Network forum, forums.irixnet.org.
  10. ↑ SGI, 007-4632-001, chapter 8, p. 144. Voltage thresholds.


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