SGI O2 Capacitor Replacement Guide
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The aged electrolytic capacitors in an SGI O2 are in its power supply. SGI's hardware reference guide treats the supply as a part to slide out and replace, and gives no component list for it or for the system board.[1] The supply is built from through-hole parts.[2] Raion, who took one apart in 2020, published the values of the capacitors on the board at its connector end.[2]
Warning: the supply runs from the mains and stays live on its standby output whenever it is plugged in. Unplug it, let the input capacitors discharge and check them with a meter before touching the boards.[3]
Signs that the supply needs work
[edit | edit source]- No LED and no fan when the power button is pressed, with the mains lead and outlet known to be good.[4]
- A supply that has failed outright. One owner repaired a failed supply by replacing its six largest output capacitors, and did the same to his spare.[2]
- On the bench, the +3.43 V output swinging high or the supply shutting down under load. Check first that both sense lines are connected, since a supply without them behaves the same way.[3]
See also Capacitor Failure Symptoms.
Supply identification
[edit | edit source]The supply measured by Elf for the TechPubs Wiki is a Sony APS-90, Sony part 8-68-1189-41, SGI part 060-0022-001.[3] Bukošek's photograph shows a transformer marked Sony.[5] Its ratings are +3.43 V 31 A, +5.1 V 10 A, +12 V 3.2 A, −12 V 0.25 A and +3.3 V standby 10 mA.[3]
Capacitor values
[edit | edit source]| Quantity | Value | Type |
|---|---|---|
| 4 | 10,000 µF 6.3 V | Axial, 105 °C |
| 2 | 2200 µF 6.3 V | Axial, 105 °C |
| 2 | 2200 µF 25 V | Axial, 105 °C |
| 2 | 220 µF 16 V | Axial, 105 °C |
| 1 | 22 µF 50 V | Axial, 105 °C |
Raion did not publish designators, and his list covers only the board on the connector side. The capacitors on the other side and on the board mounted at right angles were still to be listed when the thread ended. Record those parts from your own supply before ordering: photograph the board, then note each capacitor's position, capacitance, voltage, temperature rating, series, diameter, length and lead spacing.[2]
The owner who repaired two supplies replaced only the six largest output capacitors, the four 10,000 µF and two of the 2200 µF parts; his post does not say which voltage of 2200 µF.[2]
Opening the supply
[edit | edit source]Remove the supply from the O2 first; see General Maintenance.[1] Then, following Raion:[2]
- Free the Panaflo fan, which is held by a plastic rivet. Raion drilled it out; another owner got the rivets out undamaged.
- Remove the five screws holding the side panel and set the panel aside.
- Check the fuse for continuity.
- Unplug the fan's two-pin connector and slide the fan out. Remove the five screws and the earth lug holding the boards, including the screw inside the hole for the heavy metal tab.
- Press in the two plastic studs that hold the system connector to the frame, using needle-nose pliers, and slide the boards out as one unit with the connector.
Replacing the capacitors
[edit | edit source]- Note the polarity marking at each position before removing anything; the owner who repaired two supplies stresses checking it three times when fitting the new parts.[2]
- The large axial capacitors need a powerful iron: that owner had to buy an 80 W iron because his 40 W iron could not do it, and used fresh solder, a solder sucker and a sewing needle to clear stubborn holes. Raion could not clear the holes with a hand sucker and wick and stopped until he could get a desoldering gun. Another forum member's method is to add fresh solder, cut the old part away and pull each lead out from the component side while heating the joint.[2]
- Fit 105 °C parts of the same capacitance and at least the same voltage, matching the polarity.
- Secure the large capacitors together again: that owner used a few dabs of silicone rubber, and notes hot-melt glue would look closer to the original.[2]
- While the supply is open, consider replacing the plastic Mini-Fit connector housing, whose latches go brittle and can let the connector fall back into the supply.[2]
Checks after the work
[edit | edit source]To run the supply on the bench, connect the sense lines (pin 1 to +3.43 V, pin 13 to 0 V) and ground the run line (pin 2); the standby output on pin 15 is present as soon as mains is connected. Power good (pin 14) should rise after the +3.43 V and +5.1 V rails settle.[3] Load it before trusting the readings, since most of the O2's demand is on the +3.43 V rail.[3] Then refit it, check the fan turns, and run the IDE diagnostics; see SGI O2 Troubleshooting Guide.[6]
Related pages
[edit | edit source]- SGI O2
- SGI O2 General Maintenance
- SGI O2 Troubleshooting Guide
- SGI O2+
- Capacitor Failure Symptoms
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Silicon Graphics, O2 Workstation Hardware Reference Guide, 007-3275-002, 1996, pp. 143–151 (File:SGI O2 Workstation Hardware Reference Guide (007-3275-002).pdf). Replacing the power supply.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 "O2 PSU disassembly and refurb", IRIX Network forums, Raion and others, 14 January to 15 May 2020, forums.irixnet.org. Disassembly, capacitor list, desoldering methods, connector housing, repair by replacing six output capacitors.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 "O2 Power Supply Information", TechPubs Wiki, based on measurements posted by SGUG forum member Elf, tech-pubs.net (revision of 27 September 2025). Supply model and part numbers, ratings, standby output, sense, run and power-good lines.
- ↑ SGI, 007-3275-002, pp. 97–98, Figure 4-1. No LED: power supply failure.
- ↑ Andrej Bukošek, photograph of the inside of an O2 power supply (File:SGI O2 Sony power supply interior (Andrej Bukosek).jpg).
- ↑ SGI, 007-3275-002, pp. 99–100. Diagnostic tests.