SGI O2+ Capacitor Replacement Guide
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The capacitors most likely to matter in an SGI O2+ are in its power supply. SGI's Silicon Graphics O2+ Workstation Hardware Reference Guide treats the supply as a single replaceable unit and lists no components for it, for the system board or for the CPU modules.[1] SGI describes the O2+ as an O2 with more memory and disk, a newer processor and a purple case, and sends owners to the O2 manuals for setup and troubleshooting; it mentions no change to the supply.[2] No capacitor list for the O2+ itself has been published. For the O2 supply there is a partial list, covering the board at its connector end, and a description of its connector and outputs; both are summarised below, and the full O2 procedure is on SGI O2 Capacitor Replacement Guide.
Warning: the supply runs from the mains. SGI warns that opening covers can expose dangerous voltages.[3] Unplug the machine, take the supply out, and discharge and check its primary-side capacitors with a meter before working on the board.
The power supply
[edit | edit source]The O2+'s mains input, from SGI's specifications, is 100 to 132 V AC at 2.4 to 1.8 A or 200 to 264 V AC at 1.2 to 0.9 A, 47 to 63 Hz, with a heat dissipation of 245 W.[4] The supply slides out of the back of the case once its bezel is off and its lever is moved to the right; SGI's procedure is the same on RM7000-class and R12000-class machines.[1]
The supply in an O2 was described in detail by Elf, whose notes are now kept on the TechPubs Wiki. The unit he tested was a Sony APS-90 (Sony part 8-68-1189-41), SGI part 060-0022-001.[5] Compare the label on your own supply with this before relying on the figures below.
| Rail | Rating |
|---|---|
| +3.43 V | 31 A |
| +5.1 V | 10 A |
| +12 V | 3.2 A |
| −12 V | 0.25 A |
| +3.3 V standby | 10 mA |
Points from the same notes that matter when testing a supply on the bench:[5]
- Power goes through a 24-pin Molex Mini-Fit BMI connector, female on the supply and male on the frontplane.
- The 3.3 V standby rail is live whenever the supply is connected to the mains. Unlike the Indy and Indigo² supplies, the O2 supply does not start by itself: the Run line, pin 2, has to be grounded.
- Pin 1 is the sense line for the +3.43 V rail and pin 13 the sense line for the 0 V return. Without both connected to their rails, the +3.43 V output swings above 5 V and the supply tends to shut down under any load.
- Pin 14 is power good, asserted at 3.3 V logic level after the main rails have settled.
- Elf measured a power factor of about 0.6 and a standby draw of about 4 W.
Recapping the supply
[edit | edit source]Raion, who took an O2 supply apart in 2020, listed the electrolytics on the board at its connector end: four 10,000 µF 6.3 V, two 2200 µF 25 V, two 2200 µF 6.3 V, two 220 µF 16 V and one 22 µF 50 V, all axial 105 °C parts. He gave no board positions, and the parts on the other side and on the board mounted at right angles were not listed in the thread.[6] KiwiME brought a failed O2 supply back by replacing only the six largest output capacitors, the four 10,000 µF and two of the 2200 µF parts, and did the same to his spare.[6] The opening procedure and soldering notes are on SGI O2 Capacitor Replacement Guide. Record the remaining values from your own board (see below), and check the listed ones against it too.
A recap is not a guaranteed cure. KGLlewellyn reported a dead O2 supply that had already been recapped and still did not work; he planned to test its diodes next.[7]
System board
[edit | edit source]No component list for the O2+ system board has been published. stormy reported finding many O2s that do not respond to the power button. His own had a supply he knew to be good, and he planned to look at the MOSFETs and capacitors near the NVRAM clock chip.[8] weblacky notes that the O2 and the SGI Octane use the same Dallas real-time clock module.[9] On the Octane, Erik Baigar traced a machine that would not power on to a shorted 10 µF 16 V capacitor, C1053, beside that chip; see SGI Octane Capacitor Replacement Guide.[10] Whether the O2 board has a matching part has not been documented. Baigar's advice for the O2 was to work out the power-on circuit with a meter first, check the power button input, the clock chip's standby supply and output, the points between the MOSFETs and the line to the supply for shorts to ground or to a rail, and check every power rail on the board for shorts.[10]
Recording your own boards
[edit | edit source]Photograph each board before removing anything. For each electrolytic, note its position, value, voltage, temperature rating, diameter, height, lead spacing and polarity against the silkscreen. Order replacements by capacitance and voltage first, then by size and footprint, as Erik Baigar did for the Octane's Cherokee supply.[10]
Related pages
[edit | edit source]- SGI O2+
- SGI O2+ General Maintenance
- SGI O2+ Troubleshooting Guide
- SGI O2 Capacitor Replacement Guide
- SGI Octane Capacitor Replacement Guide
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 Silicon Graphics, Silicon Graphics O2+ Workstation Hardware Reference Guide, 007-4486-001, January 2002, pp. 149-157 (File:SGI O2+ Workstation Hardware Reference Guide (007-4486-001).pdf). Replacing the power supply.
- ↑ Silicon Graphics, Important Note: Silicon Graphics O2+ Hardware Documentation, 007-4473-001, 2001 (File:SGI O2+ Hardware Documentation Important Note (007-4473-001).pdf).
- ↑ SGI, 007-4486-001, p. 184. Safety information.
- ↑ SGI, 007-4486-001, p. 208, Table A-19. Physical environment specifications.
- ↑ 5.0 5.1 5.2 Elf, "O2 Power Supply Information", TechPubs Wiki, revision 310, tech-pubs.net/wiki/index.php/O2_Power_Supply_Information, retrieved 22 October 2026. Connector pinout, rail ratings and bench-test notes for an O2 supply. Community source.
- ↑ 6.0 6.1 Raion and KiwiME, "O2 PSU disassembly and refurb", IRIXNet forum thread 1809, 14 January to 15 May 2020, forums.irixnet.org/thread-1809.html. Partial capacitor list for the O2 supply; repair by replacing six output capacitors.
- ↑ KGLlewellyn, "Cherokee 747W Briefly Powers on then Shuts Off", IRIXNet forum thread 3932, 9 May 2023, forums.irixnet.org/thread-3932.html. A recapped O2 supply that still did not work.
- ↑ stormy, "Octane PSU repair / Cherokee...", IRIXNet forum thread 4349, 13 October 2024, forums.irixnet.org/thread-4349.html. O2s that will not power on.
- ↑ weblacky, IRIXNet forum thread 4349, 14 October 2024, forums.irixnet.org/thread-4349.html. Same Dallas clock module in the O2 and the Octane.
- ↑ 10.0 10.1 10.2 Erik Baigar (ebaigar), IRIXNet forum thread 4349, July to October 2024, forums.irixnet.org/thread-4349.html. Advice on tracing an O2 that will not power on; Cherokee recap list.