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SGI Visual Workstation 330 Capacitor Replacement Guide

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SGI Visual Workstation 330 system board layout (User's Guide Figure 3-1)
M25D system board layout (SGI User's Guide, Figure 3-1), with the two processor sockets at the lower left and the power connectors PWR1 and PWR2 on the left edge

SGI's Silicon Graphics 330 Visual Workstation User's Guide describes the SGI Visual Workstation 330 down to replaceable parts and gives no component values. The chapters on the M25D system board were written by Acer, which designed it, and no schematic or parts list for the board or the power supply has been published.[1][2] Take every value from the part on your own board.

Where the electrolytic capacitors are

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  • The power supply, which SGI treats as a sealed unit to replace whole. It is switch-selectable for 110 V or 220 V and feeds the board through two ATX connectors, PWR1 and PWR2.[3][2][4]
  • The M25D system board, around the two processor sockets (U20 and U3) and near the power connectors. SGI's layout drawing shows the sockets, slots and connectors but does not identify individual capacitors.[2]

The board is the same size and in the same chassis as the SGI Visual Workstation 230's M23D, but it is a different design, so do not take values from a 230 board.[2][5]

Signs of failure

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SGI's error messages do not point at capacitors directly. Look for domed tops, electrolyte on the board, and split or shrunken sleeves, and see Capacitor Failure Symptoms.

Recording your board

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  1. Remove the system board as described in SGI Visual Workstation 330 General Maintenance: side panel off, AGP and other cards out, cables off, loosen the board screw, pull the board away from the I/O gasket.[6]
  2. Photograph the board square-on in sections with enough light to read the sleeves, paying particular attention to the area around both processor sockets.
  3. For each electrolytic, record the printed designator, capacitance, voltage rating, temperature rating, series and can size.
  4. Note the rail each one is on by tracing it to PWR1, PWR2 or the regulator it belongs to.

Replacement

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  1. Fit parts of the same capacitance and at least the same voltage rating, in a low-ESR series where the original is one, and no larger than the original so that the processor heat sink brackets still fit.
  2. Observe polarity: the stripe on the sleeve marks the negative lead.
  3. Refit the board on its standoff hooks with the retaining bracket, tighten the screw, and reconnect every cable, including both power connectors, before the first power-up.[6]
  4. Check the BIOS and SCSISelect settings afterwards.[7][8]

Warning: SGI's guide says the power supply can hold dangerous voltages after it is unplugged.[4] Leave it unplugged until its input capacitors have discharged and confirm with a meter before touching the primary side.

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References

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  1. ↑ Silicon Graphics, Inc., Silicon Graphics 330 Visual Workstation User's Guide, 007-4278-001, June 2000, front matter (File:SGI Visual Workstation 330 User's Guide (007-4278-001).pdf). Chapters 3 and 4 provided by Acer Incorporated.
  2. ↑ 2.0 2.1 2.2 2.3 SGI, 007-4278-001, pp. 55-62, Figure 3-1 and Table 3-1. M25D board layout and components.
  3. ↑ SGI, 007-4278-001, pp. 6-7. Power supply and voltage switch.
  4. ↑ 4.0 4.1 SGI, 007-4278-001, p. 28. Dangerous voltages when unplugged; no user-serviceable parts.
  5. ↑ Silicon Graphics, Inc., Silicon Graphics 230 Visual Workstation User's Guide, 007-4263-001, March 2000, pp. 57-62 (File:SGI Visual Workstation 230 User's Guide (007-4263-001).pdf). The 230's single-processor M23D board.
  6. ↑ 6.0 6.1 SGI, 007-4278-001, pp. 42-47. Removing and refitting the system board.
  7. ↑ SGI, 007-4278-001, pp. 67-71. BIOS settings and error messages.
  8. ↑ SGI, 007-4278-001, pp. 109-116. SCSISelect settings.


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