SGI Indy Capacitor Replacement Guide

Main board of an Indy Nidec power supply. The two 680 µF 200 V input capacitors are at lower right, one under a "Caution High Voltages" sticker; brown stabilising adhesive holds several parts together (Andrej Bukošek)

The electrolytic capacitors that age in an SGI Indy are in its power supply. SGI's owner's guide treats the supply as one replaceable part and publishes no component list for it or for the system board. The Indy system board itself uses tantalum capacitors, which fail short. Two supplies were fitted, the Nidec (SGI part 9430813) and the Sony (SGI part 060-0008-001); weblacky's published rebuild work is on the Nidec.

Warning: the supply rectifies the mains onto two 200 V 680 µF input capacitors, which can stay charged after the mains lead is removed. One carries a "Caution High Voltages" sticker and the supply case has a yellow hazard label. Unplug the supply and check that the input capacitors have discharged before touching the board.

Signs that the supply needs work

• The Indy runs for a few minutes and then switches itself off as the supply warms and its outputs sag or become noisy.
• The supply is dead, with no fan and no response to the power button, or it clicks while the red LED flickers.
• The supply looks as if it is running, but its output voltages rise and fall rhythmically as it restarts over and over in protection mode.
• Scorched adhesive around the load resistors, which run hot all the time.
• Burnt or shorted tantalum capacitors on the system board, which weblacky has seen on machines run from a poorly regulated supply.

See also Capacitor Failure Symptoms.

Nidec supply (SGI 9430813)

The label reads "Nidec/Power General", model FLU5-170-1-6560, and the board silkscreen reads "Power General". No capacitor list has been published by SGI, Nidec or Power General. What the sources give:

• The two input capacitors are marked 200 V 680 µF in Bukošek's photograph of the board.
• weblacky, who rebuilds these supplies, replaces every electrolytic capacitor on the board, including the two input capacitors, with United Chemi-Con and Nichicon parts of the same or similar families. He warns against substituting low-ESR types chosen only by value: he found no controller IC in the supply, whose oscillator runs from passive parts, transistors and op-amps, so he expects it to be sensitive to ESR.
• He wrote in 2021 that the values listed on the Preterhuman wiki's Indy page agreed with the parts he removed, apart from one capacitor he thought was missing from that list, but that the list gives no diameters, lead spacings, heights or original series. He has not published his own parts list.
• He also replaces two or three load resistors whose heat discolours the surrounding adhesive, and fits parts of higher wattage.

Record your own board before ordering. For each electrolytic, photograph it in place and note its designator, capacitance, voltage, temperature rating, series, diameter, height and lead spacing; weblacky points out that diameter, lead spacing, height and series all matter when choosing replacements.

Construction points that affect the work

• The case has no screws. It is held by clips along the long top edges and comes apart along one side only; start it with a stiff putty knife and do not bend the clips.
• The small board at the front, carrying the power, reset and volume buttons and the speaker, should go back into the empty case first on reassembly.
• The long control daughterboard is tacked to the main board with adhesive and should be separated for the work. Three clusters of parts, mostly around the large chokes, are glued together, and three of the capacitors are heavily glued to their neighbours. weblacky melts through the adhesive with a knife-tip iron at about 400 °F (204 °C) and does not prise parts apart.
• The board is thin and effectively single-sided, with tracks built up with solder under a fragile solder mask, and its holes are small. weblacky says a desoldering gun is essential, and that desoldering wick will lift the tracks and pads.

Sony supply (SGI 060-0008-001)

No capacitor list or recap report for the Sony supply has been published. weblacky had not taken one apart when he documented the Nidec. Raion notes that the Sony supplies are not immune to failure and blow their MOSFETs easily.

System board tantalum capacitors

Tantalum capacitors reported failed

Board	Position	Value	Notes
Indy system board	C602	4.7 µF 20 V	On the underside; burnt on an Indy R5000 with a Sony supply. Value read from another owner's board
Indy system board	C16	Not reported	One of three yellow capacitors, C15 to C17, in a row; dexter1 reports that it sometimes blows
Challenge S system board	Not reported	10 µF 25 V	Between the GIO sockets; blew while the server kept running

dexter1 has also seen tantalum capacitors fail near the IndyCam connector; that Indy would not boot afterwards. To find a short, remove the CPU module, SIMMs and boards and measure across each tantalum capacitor; compare readings with a good board where possible, since parallel capacitors read the same. Replace a failed part with the same capacitance and at least the same voltage, and fit it with its polarity stripe the same way round as the original.

Procedure for the Nidec supply

These steps follow weblacky's published method.

1. Remove the supply from the Indy (see General Maintenance) and let it stand unplugged.
2. Open the case at the clipped side and lift out the board assembly. Clean dust out with a soft brush and compressed air, and clean the fan.
3. Separate the control daughterboard from the main board by melting through the adhesive that tacks it.
4. Photograph the board and record every electrolytic capacitor as described above.
5. Remove the capacitors with a desoldering gun, melting the adhesive away from the glued clusters first. Clean the exposed areas with isopropyl alcohol and a brush.
6. Fit the new capacitors with the polarity of the originals, and replace the hot-running load resistors.
7. Check the front-panel buttons before reassembly and replace any that are unreliable.
8. Refix the board and the glued clusters with a silicone stabiliser; another forum member suggests Dow 738.
9. Fit the front-panel board into the case first, then the main assembly, and clip the case together.

Checks after the work

weblacky's first start of a recapped supply was through a 150 W incandescent bulb as a current limiter, with loads of 2 to 3 A on the 3.3 V and 5 V outputs. His finished supplies are then loaded at 4 A on the 3.3 V and 5 V rails, checked for stability, and run in an Indy under IRIX for at least three hours.

Nidec supply outputs (label and TechPubs Wiki)

Rail	Rating	Main connector pins
+3.3 V	7 A	1, 2
+5 V	25 A	3 to 8
+12 V	4.5 A	17
−12 V	0.75 A	10

The supply runs whenever mains is applied unless the run line, pin 3 of the auxiliary header, is grounded, so it can be tested off the board; do not leave it running without a load for long. Check that the fan turns: on the Nidec it always runs. weblacky's experience is that a supply which had already stopped working usually has a damaged semiconductor as well, so a recap alone may not bring it back.

Related pages

• SGI Indy
• SGI Indy General Maintenance
• SGI Indy Troubleshooting Guide
• Capacitor Failure Symptoms
• Recommended Tools