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IBM PS2 Model 50 Hardware Maintenance Reference

From RetroTechCollection

The IBM PS/2 Model 50 Hardware Maintenance Reference is IBM's 50-page service reference pamphlet for the PS/2 Model 50 (8550). Part number 64F3989, form number S64F-3989-00, First Edition (March 1990).

What it contains

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The Hardware Maintenance Reference pamphlets all follow the same structure:

  • 1.0 Product Description — security and the cover lock, the power-on password, and the system-board features (microprocessor, CMOS RAM, ROM BIOS, video, serial and parallel ports, diskette controller, keyboard and pointing-device connectors).
  • 2.0 Option Compatibility — drive and diskette compatibility, fixed disk drives and terminators, and any adapters that are incompatible with this model.
  • 3.0 Operating Requirements — the power supply and its minimum under-voltage sense levels, the power-on self-test, and the memory subsystem with its configuration rules and error handling.
  • 4.0 Specifications — size, weight, electrical input and heat output.
  • 5.0 Special Tools — the model's own service tools.
  • 6.0 Removals and Replacements — the numbered 10xx procedures, in the order IBM intends them to be done.
  • 7.0 Locations — front, rear, interior and system-board views with connector and jumper callouts.

Model-specific removals: 1005 Cover, 1010 Battery and Speaker Assembly, 1015 Fan Assembly, 1020 Adapters, 1025 Diskette Drives and Bus Adapter, 1030 Fixed Disk Drive and Adapter, 1035 Support Structure, 1040 Power Supply, 1045 System Board, 1050 Math Coprocessor and 1055 Memory-Module Packages.

What it does not contain

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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

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This pamphlet is the source cited on IBM PS/2 Model 50 for the machine's power-supply behaviour, and it settles two things:

  • Three outputs only — +5.0, +12.0 and −12.0 Vdc. There is no −5 V rail on the Model 50. Minimum under-voltage sense levels are +4.5 V, +10.8 V and −10.2 V respectively.
  • Power off for ten seconds or more before switching back on. The supply generates its 'power good' signal on that basis, and 'power good' is what lights the green lamp on the front of the machine. "If the green light is not on, the power supply is not functioning properly." The supply also switches automatically between the 100–125 Vac and 200–240 Vac ranges.

Download it here: IBM PS2 Model 50 HMR.pdf

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