SGI Octane Capacitor Replacement Guide

IP30 system board 030-0887-003 rev F. The surface-mount aluminium electrolytics are in the audio section at the upper right; the yellow parts are tantalum chips (Mister rf, CC BY-SA 4.0)

The capacitors that matter most in an SGI Octane are in its power supply. SGI's owner's guide treats the supply as one replaceable unit and gives no component list for it or for any other module, and owners on IRIXNet report that no schematics or board views have been published. The lists below come from owners' recaps: Erik Baigar's Cherokee 747 W supply and megaimg's Lucent 623 W supply, both shopping lists by value and quantity, without board positions. System board values are read from a photograph or from repair reports. Check each value against the part on your own board before ordering.

Warning: both supplies run from the mains and hold their bulk capacitors charged after the cord is removed; the Cherokee's are 470 µF parts rated at 450 V. Discharge them and confirm with a meter before touching the boards. A Lucent supply recapped by one owner exploded at its first power-up and tripped the house breaker; bring a repaired supply up through a current-limiting lamp.

Signs of failure

• Click of death: the relay clicks when the cord goes in and nothing else happens.
• The supply starts for a moment and shuts off.
• Leaked electrolyte around the small capacitors on a Lucent supply, near a burnt diode and burnt load resistors.
• A shorted capacitor on the system board's standby rail stops the machine responding to the power button at all, with a healthy supply.

Electrolytics do not always bulge or leak when they fail; some simply dry out. See also Capacitor Failure Symptoms.

Cherokee 747 W supply

The Cherokee is the silver-handled supply, required for VPro graphics. Erik Baigar's is labelled SP360 2A, Rev A, and is built on two boards joined by a 9-pin cable. He replaced every electrolytic. His Mouser order, chosen to match capacitance and voltage first and then footprint, diameter and height, with 105 °C long-life, low-ESR parts where available:

Electrolytic capacitors replaced in a Cherokee SP360 2A supply (Erik Baigar, 2024)

Value	Rating	Qty	Part he fitted	Notes
470 µF	450 V	2	Würth 861141485033	Bulk capacitors. In one post he gives them as 450 µF
33 µF	450 V	1	Panasonic EEU-ED2W330
18000 µF	6.3 V	3	Nichicon UHE0J183MHD (1), Chemi-Con EKYB6R3ELL183MMP1S (2)
8200 µF	10 V	3	Panasonic EEU-FS1A822B
4700 µF	10 V	3	Nichicon UBT1A472MHD8
3300 µF	25 V	2	TDK B41888C5338M
2200 µF	25 V	1	Panasonic EEU-FR1E222L
1000 µF	35 V	6	Vishay MAL225090105E3 (5), Panasonic EEU-EB1V102B (1)	The 1000 µF parts include the 24 V section
330 µF	35 V	3	KEMET ESW337M035AH2AA
47 µF	35 V	2	Rubycon 35ZLH47MEFC5X11
22 µF	35 V	4	Würth 860240572002
not stated	not stated	2	Kyocera AVX REF0611101M025K	The list gives no value for this part

Erik Baigar measured the 1000 µF capacitors he took out of the 24 V section at 1000 to 1050 µF with 0.20 to 0.24 Ω ESR, against 1040 to 1080 µF and 0.15 to 0.23 Ω for the new parts, unbiased and at low current. His supply was sound before the recap; the fault that stopped his machine was on the system board.

Lucent 623 W supply

The Lucent is the black-handled supply. megaimg's unit, SGI part 060-0028-003, is built on three boards stacked in the case, with one capacitor on a small AC/DC control board mounted on the middle board. He replaced every electrolytic on all three boards. His post lists Mouser part numbers and quantities only; the values below are decoded from the manufacturers' part numbers.

Electrolytic capacitors replaced in a Lucent 060-0028-003 supply (megaimg, 2021)

Mouser number	Qty	Value and rating from the part number
647-UPJ1V102MHD6	9	Nichicon PJ, 1000 µF 35 V
75-517D476M025JA6AE3	6	Vishay 517D, 47 µF 25 V
667-EEU-FC0J682S	6	Panasonic FC, 6800 µF 6.3 V
710-861221484008	6	Würth; value not decoded
647-UPM1V222MHD1AA	2	Nichicon PM, 2200 µF 35 V
647-UVK1E101MDD	2	Nichicon VK, 100 µF 25 V
667-EEU-EB1J100S	2	Panasonic EB, 10 µF 63 V
667-EEU-FM1V681B	1	Panasonic FM, 680 µF 35 V
647-UBW1V221MPD1TD	1	Nichicon BW, 220 µF 35 V
647-UPV1H4R7MFD1TD	1	Nichicon PV, 4.7 µF 50 V

The recap alone did not revive megaimg's supply. It started after he replaced the TOPSwitch converter on the AC/DC control board and a 67F095 thermostat. Another owner reports leaking small electrolytics next to a burnt area on the third board of a Lucent supply, and suspects their failure started a chain of damage there.

IP30 system board

SGI published no component list for the IP30. In the Commons photograph of board 030-0887-003 rev F most of the capacitors are tantalum chips, marked 22 µF 10 V, 33 µF 25 V and 10 µF 16 V. The aluminium electrolytics visible are seven surface-mount cans in the audio section at the upper right, each marked 220 µF 10 V; the designators that can be read beside them are C3, C36, C47 and C52.

Erik Baigar's machine would not power on because C1053, a 10 µF 16 V capacitor on the system board next to the DS1687 real-time clock, had shorted the 3.3 V standby rail. He checked C177, a tantalum on the same circuit, as well. C177 is visible near the lower left corner of the rev F board in the photograph; his post does not say which board revision his machine had. Before replacing parts here, measure the standby rail for a short with the supply out.

Other boards

• PCI card cage 013-2304-001: tantalum C25 exploded on one owner's cage. weblacky read it from his own cage, a different revision, as 22 µF 35 V.
• ESSI (SSE) graphics board 030-1240-005 rev D: capacitors C234 and C79A were damaged on one failed board, beside a burst chip at U8. Their values have not been published.

Recording your own board

Where no list exists, photograph each board before removing anything, then note each capacitor's position, value, voltage, temperature rating, diameter, height and lead spacing, and its polarity mark against the silkscreen. megaimg advises keeping track of every screw and labelling the mains input wires by colour before disconnecting them.

Procedure

Lucent supply, following megaimg's disassembly:

1. Remove the supply from the Octane (see SGI Octane General Maintenance) and open its case.
2. Remove the top board, held by four screws, after unplugging the cable that joins it to the middle board. Free its wires from the white external connector by pushing the contacts out with fine needle-nose pliers; leave the connector on the board.
3. Label and disconnect the mains input wires from the middle board, remove its two screws, unplug the cable to the bottom board and lift the middle board out.
4. Remove the bottom board, held by four screws. Unplug the fan and feed its cable back between the heat sinks, and free the second white connector as before.
5. Replace the electrolytics on all three boards, including the one on the small AC/DC control board.

Cherokee supply, following Erik Baigar's work:

1. Separate the two boards, which are joined by a 9-pin cable.
2. For bench testing, remove the bulk capacitors or fit much smaller ones (he used 22 µF), and feed the boards from a current-limited DC supply at reduced voltage (he used 64 V). He found the standby (kick-start) converter on the first board runs once the rectified voltage passes about 60 V.
3. Replace the electrolytics from the list above.
4. Bench test with a resistive load of at least 1 A on each output, from the mains through an isolating transformer. Pull the INHIBIT line low to start the supply: the relay that brings in the PFC stage and bypasses the inrush thermistors should click in at once, every output should come up, and the power-good signal should follow after about 500 ms.

Erik Baigar's Cherokee documentation lists +3.45 V, +5 V, +12 V and +24 V outputs, plus the 3.3 V standby that powers the system board's real-time clock.

Related pages

• SGI Octane
• SGI Octane General Maintenance
• SGI Octane Troubleshooting Guide
• SGI Octane2 Capacitor Replacement Guide
• Capacitor Failure Symptoms
• Recommended Tools