SGI Crimson Capacitor Replacement Guide

Leaking Elna 1000 µF 10 V capacitors taken out of the 5 V module of a Crimson's Power-One supply (jan-jaap)

The electrolytic capacitors that fail in an SGI IRIS Crimson are mostly in its power supply. SGI's installation and upgrade guides treat the supply as one replaceable unit and give no component values for it or for any Crimson board. The values below come from owners who have rebuilt the Power-One SPM5 supply, mainly dexter1's full recap of his Crimson's supply in 2020 and jan-jaap's rebuild in 2022. They are what was found in individual units, not a parts list. Check every part on your own supply before ordering.

Warning: the supply's input module and internal bus carry about 300 V DC from rectified mains, and about 70 V can remain on the main filter capacitors more than ten minutes after power is removed. Large parts of the supply are not isolated from the mains.

Signs of failure

• Brown electrolyte on the boards of the output modules, and lacquer lifting from the copper where it has soaked in. dexter1's 5 V module was so wet that the fluid had collected in pockets under the solder resist.
• Bulging capacitors on the underside of the supply's backplane board; all of dexter1's 47 µF 35 V parts there had bulged.
• Corroded pads that solder will not wet, and tin missing from the pads around a leaked capacitor.
• An acid smell when the system is switched on.
• Electrical symptoms: outputs that turn on with the front switch off, over-voltage LEDs on the status panel, the supply switching its outputs on and off rapidly, or the system rebooting after running for a while. See SGI Crimson Troubleshooting Guide.

See also Capacitor Failure Symptoms.

Which supply is fitted

Remove the plastic back panel and the metal sheet behind it. A silver supply above the mains inlet is a Power-One SPM5; a black one is a Cherokee. The SGI Power-One is type SPM5-AD-AE-LB-S180: an input module, a backplane board, an AD output module for 5 V at 170 A and an AE module for +12 V, −12 V and −5 V. No owner's capacitor list for the Cherokee supply has been published. Geoman's repair notes on one describe a charred section around its feedback circuit and give no capacitor values.

Power-One SPM5 capacitors found by owners

SGI and Power-One published no values for this supply. The owners' reports name only one designator, C12 on the AE module.

Capacitors reported in the SGI Power-One SPM5 (owner repair logs)

Part of the supply	Capacitors reported	Notes
Input module, rectifier and filter	Two banks of three 1500 µF main filter capacitors (voltage not stated)	jan-jaap measured them good and left them in place; replacements would have cost about US$100 and were hard to find. The film capacitors on this board had cracked with age and he replaced them
Backplane (base connector board)	13 capacitors, including the 47 µF 35 V parts	All the 47 µF 35 V parts were bulging on dexter1's board. GanjaTron found the backplane capacitors "leaking all over the place" in two supplies
Base daughter board	2 capacitors (values not stated)	Replaced by dexter1
5 V, 170 A module (AD)	9 × 1000 µF 10 V, Elna CERS, 105 °C, 12.5 × 40 mm, 5 mm pitch 2 × 1000 µF 10 V, Nichicon, 105 °C, 13 × 25 mm, 5 mm pitch 1 × 470 µF 10 V, 105 °C, 8 × 12 mm, 5 mm pitch 3 × 47 µF 35 V, Nichicon, 105 °C, 8 × 12 mm, 4 mm pitch	dexter1's list for his module. The Elna parts had leaked badly in both dexter1's and jan-jaap's supplies. jan-jaap's photograph of the parts from his 5 V module also shows a Nichicon 2200 µF 10 V capacitor, which is not in dexter1's list
+12 V, −12 V, −5 V module (AE)	3 Nichicon electrolytics (values not stated)	All three had started to leak on dexter1's module; jan-jaap found the same module badly contaminated

dexter1 counted 34 electrolytic capacitors in his supply and replaced them all with the same values. He advises replacing every electrolytic in the supply except perhaps the large filter capacitors on the mains side, and checking those by measuring the bus voltage.

Write down the value, voltage, temperature rating, size and lead pitch of every capacitor on your own modules before removing anything, and photograph each board. The 5 V module's Elna parts are 40 mm tall and 12.5 mm across, and dexter1 chose some of his replacements for their lead pitch.

System boards

SGI published no capacitor lists for the IP17, IO3B, PS3, PP2 or graphics boards. Owners' reports:

• CB_HK's system rebooted after about 20 minutes even with a repaired supply. He never found the single bad capacitor, but after replacing every electrolytic he could find, including those on the backplane, the system was stable.
• Geoman replaced all the capacitors on the boards of his Crimson and found one leaked capacitor whose electrolyte had eaten into three copper traces under the silkscreen.
• jan-jaap's photograph of a PS3 status panel board shows one small radial electrolytic, beside the flat-cable connector.

Replacement procedure for a Power-One supply

1. Take the supply out of the system. Before taking it apart, note the mains link on the input terminal block and photograph the DIP switch settings on the supply's backplane.
2. Separate the modules. The SPM5 is modular, so each output module and the input module can be removed and worked on alone.
3. Desolder the capacitors. dexter1 needed a 40 W iron because the solder melts at a higher temperature than usual; jan-jaap bought a desoldering station after doing his first module with braid.
4. Clean off the electrolyte. dexter1 scrubbed his 5 V board with soapy water and a toothbrush, rinsed it in demineralised water twice and left it to dry for about a week. robespierre points out that capacitor electrolyte is acidic and is neutralised with sodium bicarbonate solution, not vinegar, and that flammable solvents must not be used in an ultrasonic cleaner.
5. Restore corroded pads before soldering. robespierre suggests a fibreglass pen to get back to bright copper, then activated rosin flux and a cool iron for tinning. dexter1 recommends also replacing ICs and small glass diodes in areas where electrolyte had reached their pins.
6. Fit new 105 °C low-ESR capacitors of the same capacitance and at least the same voltage. jan-jaap recommends Panasonic FR series for this supply; dexter1 used Panasonic FR and Würth Elektronik parts where he needed a smaller lead pitch or an unusual value. Observe polarity.
7. Renew the thermal compound on the heat sinks you disturb, including the rectifier's.
8. Re-secure components with a non-corrosive silicone. jan-jaap's supplies used a rubbery sealant where wires meet the boards; forum members recommended DOWSIL 738 or a similar electronics-grade product, and robespierre warns against acetoxy-cure silicone, which gives off a corrosive by-product.
9. Bench-test the reassembled supply before refitting it, as described in SGI Crimson Troubleshooting Guide#Bench-testing a Power-One supply.

After recapping

Check that the internal bus reads about 300 V DC with the outputs inhibited, and that each output shows its voltage once the inhibit is released. SGI's ratings for the supply as configured are 5 V at 170 A, −5 V at 5 A, +12 V at 16 A and −12 V at 7 A, for 1050 W in total. Run it under load for a while before refitting it; jan-jaap ran his for a couple of hours at 40 A.

Related pages

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