IBM PS2 Model 55 SX Hardware Maintenance Service
The IBM PS/2 Model 55 SX Hardware Maintenance Service is IBM's 35-page service pamphlet for the PS/2 Model 55 SX (8555). Part number 91F8637, form number S15F-2195-02, © IBM 1991.
Its own front matter describes it as containing "procedures for isolating problems to a FRU, a Symptom-to-FRU Index, and a parts listing", to be used with the general Hardware Maintenance Reference (15F2190 / S15F-2190-00) and Hardware Maintenance Service (15F2200 / S15F-2200-00) volumes.
What it contains
[edit | edit source]- 1.0 General Checkout and 2.0 Installed Devices List — automatic configuration, device types, SCSI and non-SCSI devices.
- 3.0 Power-On Password and 4.0 Undetermined Problem.
- 5.0 Power Supply Voltages / Fan — the bench measurements, below.
- 6.0 Enable and Disable Settings — SCSI presence error reporting, set from Set and View SCSI Device Configuration.
- 7.0 Display Self-Test, 8.0 Display Adapter 8514/A, 9.0 Keyboard, 10.0 Printer, 11.0 Memory.
- 12.0 Symptom-to-FRU Index, 13.0 How To Use This Parts Catalog, 14.0 System Overview, 15.0 Parts.
What it does not contain
[edit | edit source]Module level only. IBM serviced these machines by field-replaceable-unit exchange, and this pamphlet reflects that: it names FRU part numbers, not component values. There is no capacitor list, no resistor list, no semiconductor list and no schematic anywhere in it. The power supply, the planar and each drive are single line items in the parts catalogue. This is why no IBM machine checked in this wiki's verification drive has a published component-level capacitor list — it is not that the manuals were lost, it is that IBM never wrote one.
It is also not a standalone book. IBM issued it as a pamphlet to be filed in a binder alongside the general-purpose IBM Personal System/2 Hardware Maintenance Reference (part number 15F2190, form number S15F-2190-00) and Hardware Maintenance Service (part number 15F2200, form number S15F-2200-00), which carry the safety information, the general checkout procedure and the option and adapter sections. Those two general volumes are not hosted here.
What it settles
[edit | edit source]The power supply check. Power off, remove connectors P7 and P14 from the system board, power on, and measure. IBM gives the checks as lead placements and does not name the rails:
| V dc minimum | V dc maximum | − lead | + lead |
|---|---|---|---|
| +4.8 | +5.2 | P7-5 | P7-10 |
| +4.5 | +5.4 | P7-9 | P7-5 |
| +11.5 | +12.6 | P7-5 | P7-3 |
| +10.8 | +12.9 | P7-4 | P7-8 |
| +4.8 | +5.2 | P14-1 | P14-3 |
| +4.8 | +5.2 | P14-1 | P14-4 |
| +4.8 | +5.2 | P14-2 | P14-5 |
Two of the P7 checks are taken with the negative lead on a pin other than the one IBM uses as return elsewhere in the table, which is how IBM specifies checking a supply of the opposite polarity. Compare IBM PS2 Model 55 Technical Reference (October 1990), which states that the system-board voltages are +5, +12 and −12 Vdc. If the voltages are wrong or the fan is not running, check the power cord for continuity; if the cord is good, replace the power supply.
Download it here: IBM PS2 Model 55 SX HMS.pdf