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IBM IntelliStation Capacitor Replacement Guide

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IBM IntelliStation Z Pro 6221
IBM IntelliStation Z Pro Type 6221.

IBM published no capacitor list for any IBM IntelliStation system board or power supply. Its hardware maintenance manuals treat the system board, the power supply and each adapter as field-replaceable units with part numbers, and give no component values or schematics.[1] A recap therefore starts by reading the values from the board in front of you.

Many IntelliStations date from the years of the "capacitor plague", when aluminium electrolytic capacitors with faulty electrolyte failed early. Wikipedia dates the problem to capacitors made between 1999 and 2007, most of them produced from 1999 to 2003 and failing between 2002 and 2005, and names IBM among the affected vendors.[2]

Safety

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The power supply's primary capacitors are charged from the mains and can hold a charge after the machine is unplugged. Unplug the machine, discharge the primary capacitors through a suitable resistor and confirm with a meter before working on a supply. Use an anti-static strap for system board work.

What is known about specific boards

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The Z Pro 6221 system board is MSI's MS-9121. A badcaps.net member who compared an IBM board with MSI's published pictures found that IBM's version uses Sanyo OS-CON polymer capacitors where MSI used other polymers, and Rubycon electrolytics at the processor voltage regulator where MSI's board had Nichicon; the rest were Sanyo on both.[3] The thread reports the parts fitted, not a failure.

Rubycon MBZ capacitors can fail without bulging. The founder of badcaps.net reported a batch of 30 IBM/Lenovo ThinkCentre boards with 1000 µF 10 V Rubycon MBZ capacitors (date codes 2006 to 2008) that were far out of specification with flat tops and clean vents: one measured 2.78 µF at 27 Ω ESR. The boards would not POST, or crashed, until every MBZ was replaced.[4] These are ThinkCentre boards, not IntelliStations, but the lesson applies to any IBM board of the period: a capacitor that looks healthy can still have failed.

Inspection

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  1. Unplug the machine and remove the cover following the procedure for its type.
  2. Look at every aluminium electrolytic on the system board, concentrating on the processor voltage regulator: domed or split tops, electrolyte residue at the base, or a capacitor lifted off the board.
  3. Note the make, series, capacitance, voltage and date code of each.
  4. Because a failed capacitor may look normal, measure capacitance and ESR out of circuit when the machine is unstable and nothing is visibly wrong.
  5. Photograph both sides of the board before removing anything.

Symptoms that point to capacitors are described in Capacitor Failure Symptoms and in IBM IntelliStation Troubleshooting Guide.

Replacement

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  1. Record every capacitor's position, polarity, value, voltage and diameter from the board and the photographs.
  2. Remove the system board from the chassis. Its removal procedure is in the HMM or installation guide for the type.
  3. Desolder each capacitor; add fresh solder and flux first to help it flow. Voltage regulator ground pads sit on large copper areas and need more heat.
  4. Clear the holes with solder wick or a desoldering tool.
  5. Fit replacements of the same capacitance and the same or higher voltage rating, of a low-ESR series with a ripple current rating at least that of the original. Where the original is a polymer (OS-CON or similar), fit a polymer.
  6. Match polarity to the board marking and to your photographs.
  7. Refit the board and check that POST completes, then run IBM's diagnostics or a memory test, then a long load test.

Check the polarity of every position against the photographs before power-up.

Power supplies

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IBM rated the supplies by type (145 W on the E Pro 6893, 200 W on the Z Pro 6899, 330 W on the 6865, 6889 and 6898, up to 815 W on the Z Pro 9228) and listed them as single FRUs.[1][5] Identify the supply from its own label and read its capacitors from its board. After a recap, check the outputs against the ATX limits in the maintenance guide before reconnecting the system board.

References

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  1. ↑ 1.0 1.1 IBM, IBM Personal Computer 300 Series, 700 Series, IntelliStation Hardware Maintenance Manual, S83G-7789-17, September 1998, parts lists pp. 114 to 143. Hosted here as File:IBM PC 300 700 IntelliStation Hardware Maintenance Manual S83G-7789-17 (Sep 1998).pdf.
  2. ↑ Capacitor plague, Wikipedia (secondary source).
  3. ↑ "MSI MS-9121 vs IBM Z-pro Intellistation 6221", badcaps.net forum, February 2009 (a user's comparison, not a manufacturer document).
  4. ↑ "Scary Trend of Rubycon MBZ failures - No bloating!!", badcaps.net forum, March 2012.
  5. ↑ IBM Support, "Overview - IBM IntelliStation Z Pro (Type 9228)": 815 W voltage-sensing power supply with PFC.
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