SGI Indigo Capacitor Replacement Guide
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The electrolytic capacitors that owners replace in an SGI IRIS Indigo are in its power supply.[1][2] SGI's owner's guide treats the supply as a part to slide out and replace and gives no component list for it.[3] The supplies were not designed by SGI, and no schematic for them is known.[4] One owner who examined the backplane found only passive parts and the address EEPROM on it, with no electrolytic capacitors.[2] The IP12 CPU board's schematic shows a number of polarised capacitors, listed below.[5]
Warning: the supply runs from the mains. Unplug both power cables, let the input capacitors discharge and check them with a meter before touching the board.[3]
Signs that the supply needs work
[edit | edit source]- No LED, and the supply fan above the power sockets at the back is not turning. SGI's guide treats this as a failed supply.[6]
- A supply that will not start. The owner of one failed R4400 supply notes that it needs a load on the 5 V rail before it will start on the bench, so test it loaded before condemning it.[7]
- Corroded or burnt parts. One owner found two corroded rectifier diodes on a PEC4044B daughterboard; another found a shorted diode in a supply whose transistors a previous owner had replaced as burnt.[1]
See also Capacitor Failure Symptoms.
Supply identification
[edit | edit source]| Machine | Supply | Notes |
|---|---|---|
| R4400 (IP20) | ITT PowerSystems PEC4044B, part 6064459 Rev F | Owner believes R3000 machines use a different supply[1] |
| R4400 (IP20), a second machine | Not named | 5 V rail rated 34 A; needs a 5 V load to start[7] |
| R3000 (IP12) | Not named | Owner of one replaced four 3300 µF capacitors[2] |
An R3000 Indigo converted to R4000 needs the R4000-family supply as well as the board.[8] One owner believes he damaged a supply by fitting an R4000 board to a machine with the R3000 supply.[9]
Capacitor values
[edit | edit source]The capacitor lists that owners have posted for both supplies are attachments on the IRIX Network forums, which need a forum login to view. The owner who recapped a PEC4044B posted his list in October 2025, with physical sizes measured by ruler, and chose parts that met or exceeded the original ratings.[1] Another owner posted a parts list for an R3000 supply rebuild in May 2022; weblacky, replying, praised the UPM and UPJ series and said he uses them a lot in Indy supplies.[10]
Before ordering, record each electrolytic from your own supply: photograph the board, then note its position, capacitance, voltage, temperature rating, series, diameter, length and lead spacing, and mark the polarity on the photograph.
Removing the supply
[edit | edit source]Remove the supply from the machine as described in General Maintenance: front cover off, one Phillips screw out at the back, and push the supply out towards the front by pressing on its power sockets.[3]
Working on the PEC4044B
[edit | edit source]Notes from the owner who recapped one in 2025:[1]
- The board is thick and some leads go into a heavy ground plane, so a decent temperature-adjustable iron is needed.
- The leads are bent over on the underside at an angle, so a desoldering gun cannot be put over the lead ends.
- Two diodes on the daughterboard, CR207 and CR209, marked FE5D, were corroded. weblacky found a datasheet for the FE5D, a glass-passivated fast efficient rectifier, and the owner confirmed the match. The owner found no modern equivalent in stock and bought old-stock FE6D diodes, which he describes as identical apart from a 6 A rating in place of 5 A. Another forum member thought cleaning them would be enough; weblacky advised replacing them because the corrosion may mean the seal has failed.
- On another PEC4044B, a shorted diode, CR106, stopped the supply. A previous owner had already replaced the transistors Q103 and Q104 as burnt; on the first owner's supply they are marked National 2N4400 and Supertex VN0655. Once CR106 was replaced the supply worked, and the replacement transistors were fine as fitted.
Checks after the work
[edit | edit source]- Load the supply before measuring. One owner loaded the 5 V and 12 V rails with two car bulbs of about 50 W each.[1] Another notes that the supply will not start without a load on 5 V.[7]
- Check that the fan runs. After one recap the fan did not turn although the 12 V rail measured 12.3 V and the fan worked in another supply; the owner had not checked the fan before starting.[1]
- Refit the supply fully home in its connector; a supply that is not fully seated can leave the +12 V rail at about 2.2 V.[11]
- Power on and watch the front LED, then run the diagnostics; see SGI Indigo Troubleshooting Guide.[6]
CPU board (IP12)
[edit | edit source]SGI's HP1 schematic for the IP12 board gives values but no voltage ratings. Most of the polarised capacitors on it are in the audio power supply on sheet 29, where 78L05 and 79L05 fixed regulators and LM317 and LM337 adjustable regulators, fed from +12 V and −12 V, make the analogue supplies for the converters, op-amps and speaker amplifier.[5] Values are as printed on the drawing:
| Designator | Value on drawing | Position |
|---|---|---|
| C29 | 33uF_AVX | +12 V input, after L10 |
| C562 | 33uF_AVX | −12 V input, after L8 |
| C542 | 0.33uFSM | Input of U15 (78L05) |
| C535 | 0.33uFSM | Input of U14 (78L05) |
| C529 | 47uF_AVX | Output of U14, AV+5 |
| C545 | 0.33uFSM | Input of U19 (79L05) |
| C557 | 47uF_AVX | Output of U19, AV−5 |
| C539 | 0.33uFSM | Input of U13 (LM317) |
| C14 | 47uF_AVX | Output of U13, AV+ (op-amp supply) |
| C558 | 0.33uFSM | Input of U20 (LM337) |
| C15 | 47uF_AVX | Output of U20, AV− (op-amp supply) |
| C556 | 1.0uFSM | Input of U25 (LM317T) |
| C561 | 1.0uFSM | Output of U25 |
| C567 | 47uF_AVX | AV+HP (speaker and headphone amplifier) |
| C568 | 1.0uFSM | Input of U26 (LM337T) |
| C569 | 1.0uFSM | Output of U26 |
| C22 | 47uF_AVX | AV−HP (speaker and headphone amplifier) |
Polarised capacitors noticed on other sheets include C588 (2.2uFCSM) at the input and C605 (1.0uFSM) at the 8 V output of regulator U50 (78M05DT) on sheet 15, C576 (1.0uFSM) on the clock driver supply on sheet 26, and C506 (10uF_ADC) on the VREF pin of the CS5336 converter on sheet 32.[12] The list above is not a complete survey of the board. Check the board and the schematic before ordering, and measure or read the voltage from the fitted part, since the drawing does not give it.
No schematic for the IP20 board was found.
Related pages
[edit | edit source]- SGI Indigo
- SGI Indigo R4000
- SGI Indigo General Maintenance
- SGI Indigo Troubleshooting Guide
- SGI Indigo Documentation
- Capacitor Failure Symptoms
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 "Help identifying Indigo PSU components?", IRIX Network forums, 9 October to 29 November 2025, forums.irixnet.org. PEC4044B recap, FE5D diodes, CR106, Q103 and Q104, bulb loads, fan.
- ↑ 2.0 2.1 2.2 "IRIS Indigo no gfx card detected", IRIX Network forums, January 2025, forums.irixnet.org. R3000 supply with four 3300 µF capacitors replaced; backplane has no electrolytic capacitors.
- ↑ 3.0 3.1 3.2 Silicon Graphics, IRIS Indigo Workstation Owner's Guide, 007-9065-050, 1996, pp. 151–155 (File:SGI IRIS Indigo Workstation Owner's Guide (007-9065-050).pdf). Replacing the power supply.
- ↑ "Iris Indigo pops GFI when powered on", IRIX Network forums, weblacky, 28 October 2025, forums.irixnet.org.
- ↑ 5.0 5.1 5.2 Silicon Graphics, HP1 schematic, 032-8044-003 rev C, 31 October 1991, sheet 29, "Audio Power Supply" (File:SGI IRIS Indigo IP12 (HP1) CPU board schematic (032-8044-003 rev C).pdf).
- ↑ 6.0 6.1 SGI, 007-9065-050, pp. 112–113. No LED: check the fan at the rear.
- ↑ 7.0 7.1 7.2 "Indigo R4400 PSU Repair", IRIX Network forums, 18 April 2026, forums.irixnet.org.
- ↑ Kaya Kupferschmidt, "The SGI IRIS Indigo", hardware.majix.org, 2003, hardware.majix.org. Upgrading from R3000 needs the board and the power supply.
- ↑ "Help me fix this PSU", IRIX Network forums, 27 July 2026, forums.irixnet.org.
- ↑ "Indigo R3000 PSU Rebuild", IRIX Network forums, 27 May 2022, forums.irixnet.org.
- ↑ "Need troubleshooting help with Indigo (2.2v on 12v rail)", IRIX Network forums, May 2026, forums.irixnet.org.
- ↑ SGI, HP1 schematic, 032-8044-003 rev C, sheets 15 (SCSI and keyboard/mouse), 26 (GIO clocks) and 32 (audio line in).