IBM 5120 Maintenance Information Manual
The IBM 5120 Maintenance Information Manual, order number SY34-0192-0 (December 1979), is IBM's field service manual for the IBM 5120 Computing System, which IBM designates internally as the 5110 Model X3X. 324 pages.
What it contains
[edit | edit source]- Locations (section 2) — including 207 AC Box (power on/off switch, terminal blocks TB1 and TB2, a sealed line filter module, circuit breaker CB1 and the AC line cord) and 208 Power Supply, which identifies the AC box, PC Board A1 with fuses F2 (+5 Vdc), F3 (−5 Vdc) and F4 (+24 Vdc), the resonant capacitor C4, PC Board A2 carrying the AC1/AC2 inputs and the output terminals E1 to E14, transformer T1, circuit breaker CB1 and the diskette AC connectors P4 and P5.
- 272 Power — Y1 Socket Pin Assignments — the Y1 cable to A1 board pin map and the DC rail tolerance table for loaded and unloaded conditions.
- 273 AC Voltage Distribution, 274 DC Voltage Distribution and 284 Internal Diskette DC Voltage Distribution (including load resistor RL1).
- Maintenance analysis procedures, with a dedicated Power 700 MAP set, plus diskette, display, keyboard and communications MAPs and the error-code and device-address summary.
Section 208 is the reason this manual matters for restoration: it is the only IBM document on this wiki that names a capacitor in the 51xx family as a functional part rather than a stores item. C4 is the resonant capacitor of a ferroresonant supply — an AC-rated part that sets the regulation, not a smoothing electrolytic.
What it does not contain
[edit | edit source]No capacitance values, and no component-level parts list. The scan has no text layer, so it cannot be searched; pages must be read by eye.
Download the IBM 5120 Maintenance Information Manual here: IBM 5120 Maintenance Information Manual SY34-0192-0.pdf