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SGI Onyx 3000 Capacitor Replacement Guide

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SGI Onyx 3000 rack with G-brick (Owner's Guide Figure 1-1)
Onyx 3000 rack: the power bay at the bottom feeds 48 V to the C- and I-bricks, while the G-brick at the top has its own mains supply (SGI Owner's Guide, Figure 1-1)

Capacitor notes for the SGI Onyx 3000. SGI's owner's guide treats the power bay supplies, the bricks and the G-brick as units for its own engineers and gives no component lists or capacitor values for any of them.[1][2] No owner has published a capacitor list for an Onyx 3000 or Origin 3000 brick or power supply either. The values in your system have to be read from the parts themselves; do not fit values copied from another machine.

Warning: the power bay supplies, the G-brick supply and the D-brick supplies all run from the mains, and their input capacitors can hold a dangerous charge after the cord is pulled. SGI also warns that the brick midplanes carry voltage even when the system has been reset or halted.[1] Unplug everything, 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 the Onyx 3000 (SGI Owner's Guide and owners' notes)
Assembly What is documented
Power bay Up to six supplies of 950 W each, 4.4 kW in all, with eight 48 V DC outputs; each supply has its own 200–240 V, 20 A input cord from the PDU. The bay is 3U and weighs 33 kg with six supplies.
Bricks fed from the power bay C-, I-, P-, X-, N-, R- and V-bricks and the L2 controller take 48 V DC and make their own lower voltages.
X-brick power board Carries the L1 controller logic, five VRMs, one DC-DC converter and three voltage regulators that convert the 48 V for the brick.
P-brick power board Feeds the twelve PCI slots, on average 17.5 W (5.3 A at 3.3 V) per slot, under the control of the L1.
G-brick Its own supply, 180–254 V AC, up to 2000 W, with its own cord to the wall.
D-brick Two 550 W supplies, 180–254 V AC, fed from the power distribution strip.

[3][4]

jan-jaap, a long-time collector, describes the brick converters as replaceable modules, not parts soldered to the boards.[5] SGI's guide does not identify the converter modules or their makers.

What owners have found

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No owner reports of failed capacitors in Onyx 3000 or Origin 3000 power bay supplies, G-brick supplies or bricks have been found. The faults owners do report on these bricks are monitoring chips and L1 controllers, covered on SGI Onyx 3000 Troubleshooting Guide.[6][7] For the later Origin 350 and Onyx 350 compute modules, which use a different supply and boards, owners' repairs of regulators and supplies are on SGI Origin 350 Capacitor Replacement Guide.

Recording your own system

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  1. Power the system down from the L2, turn off the PDU and PDS breakers and the rear switches of the G-bricks, and unplug every cord.[1]
  2. Photograph both sides of each board or supply before desoldering anything, with designators readable.
  3. For each electrolytic or polymer capacitor, write down the designator, capacitance, voltage rating, temperature rating, maker and series, size and polarity.
  4. Look for domed tops, leakage at the base, brown or crystalline residue and corroded traces near capacitors.
  5. 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
Power bay supply
G-brick supply
Brick power board or converter module
D-brick 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 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. Reconnect the brick or supply and power the system up from the L2.[1]
  2. Check the brick's rear 12 VDC and 48 VDC LEDs, and that its front panel shows no service-required or failure light.[8]
  3. Run env on the brick. Every voltage should be inside its warning limits; SGI counts 10% from nominal as a warning and 20% as a fault.[9][10]
  4. Measure the rails you worked on with a meter as well, so that a faulty 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, 007-4264-002, chapter 4, pp. 92–119. Maintenance and safety, voltage in the midplanes, powering off.
  2. ↑ SGI, 007-4264-002, chapter 5, pp. 121–125. Customer-replaceable units.
  3. ↑ Silicon Graphics, SGI Onyx 3000 Series Graphics System Hardware Owner's Guide, 007-4264-002, November 2001, chapter 1, pp. 4–5, Table 1-1 (File:SGI Onyx 3000 Series Graphics System Hardware Owner's Guide (007-4264-002).pdf). Power bay, PDU, PDS and G-brick power cables.
  4. ↑ SGI, 007-4264-002, appendix A, pp. 143–146, Tables A-4 to A-6. Power bay and brick power, X-brick and P-brick power boards.
  5. ↑ jan-jaap, reply of 17 January 2019 in "Proactive maintainability of SGI Power Supplies, thoughts?", IRIX Network forum, forums.irixnet.org.
  6. ↑ jan-jaap, reply of 27 September 2023 in "Origin 350 - PCI 5V missing", IRIX Network forum, forums.irixnet.org.
  7. ↑ jan-jaap and jpstewart, replies of 12–13 November 2020 in "CBRICK Error", IRIX Network forum, forums.irixnet.org.
  8. ↑ SGI, 007-4264-002, chapter 2, pp. 36–60. Brick front and rear LEDs.
  9. ↑ SGI, 007-4264-002, chapter 6, p. 132, Table 6-2. Voltage warning and fault thresholds.
  10. ↑ Silicon Graphics, SGI L1 and L2 Controller Software User's Guide, 007-3938-006, chapter 3, pp. 66–68 (File:SGI L1 and L2 Controller Software User's Guide (007-3938-006).pdf). env command.


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