IBM 5110 Capacitor Replacement Guide
The IBM 5110 Computing System uses the same design of DC supply as the IBM 5100: a transistor switching regulator producing +5, −5, +8.5, +12 and −12 V, with the same tolerances, protection trip points and five-second restart rule.[1] The rail tables and general method on the IBM 5100 Capacitor Replacement Guide apply.
IBM's 5110 maintenance manual, MAPs and system logic manual give no capacitance values for the 5110 system unit. The logic manual draws the regulator board as a block with numbered output terminals.[2] What is specific to the 5110 is the terminal map on the supply board and the IBM 5114 Diskette Unit, a separate mains-powered box with a ferroresonant supply, published ripple limits and capacitor part numbers.
Safety
[edit | edit source]- The 5110 and the 5114 have separate line cords and separate supplies. Unplug both before opening either.
- Both supplies have capacitors that hold charge after power-off. Discharge through a resistor and confirm with a meter.
- The display is fed low-voltage DC but generates its own high voltage for the tube. Follow the CRT Discharge Procedure.
- The 5110 AC power box carries mains to the line filter, fuse, power switch, cooling fan and tape unit motor.[2]
The 5110 system unit
[edit | edit source]Measuring the rails at the supply itself
[edit | edit source]The supply board brings each rail out to terminals E1 to E14, which IBM's note says are shown as they are physically located on the board:[2]
| Terminals | Rail |
|---|---|
| E1, E2, E3 | +5 V |
| E4, E5, E6 | Ground |
| E7, E8 | +8.5 V |
| E9, E10 | +12 V |
| E11, E12 | −12 V |
| E13, E14 | −5 V |
Measuring here separates a supply fault from a load fault. Judge the readings against the loaded and unloaded tolerances in the 5100 table, which the 5110 MIM repeats unchanged.[1]
The AC power box
[edit | edit source]The 5110 AC box holds line filter L1, AC capacitors C1 and C2, fuse F1 and plug sockets J1, J2 and J3.[3] C1 and C2 are the only capacitors IBM identifies by designator in the 5110 system unit, and no value or rating is published for them. They are on the mains side, so a replacement must match the capacitance and have at least the original's AC voltage rating and safety class, as printed on the part.
The tape unit has one more capacitor, for its AC motor, shown without a designator on IBM's tape unit location drawing.[4] IBM's Tape Read MAP names a bad tape motor start capacitor, alongside the tape motor assembly and its cable, when the motor will not run even with its plug moved to the supply's AC socket J1.[5]
IBM's grounding advice includes checking that the AC box capacitors are not twisted with their wires crossed, since crossed line and load wiring can couple line spikes into the load side.[6]
Three supplies were offered, for 100–124 V 50/60 Hz, 200–235 V 50 Hz and 235 V 50 Hz (UK); the input connection does not change with voltage.[2] Check which supply is fitted before powering a machine from another region.
The IBM 5114 Diskette Unit
[edit | edit source]Supply
[edit | edit source]IBM: "The 5114 uses a ferroresonant power supply that develops three DC voltages."[7]
| Rail | Feeds | Range |
|---|---|---|
| +5 V | A1 board and the I/O interface port (the 5110's +5 V is not used in the 5114) | +4.6 to +5.5 V |
| −5 V | A1 board | −4.6 to −5.5 V |
| +24 V | Diskette control card | +21.6 to +26.8 V |
Peak-to-peak ripple must not exceed 0.16 V on +5 V and −5 V, or 0.8 V on +24 V. Input voltage may vary ±10 %, and input frequency by no more than ±0.5 Hz.[7] Measure ripple with an oscilloscope on a running unit.
The supply, including its AC input and DC output cables, is a field-replaceable unit that needs no adjustment. A fuse protects it: an overloaded or short-circuited output blows the fuse and the supply shuts down.[7]
Components IBM identifies
[edit | edit source]The power supply location drawing shows terminal block TB1, transformer T1, capacitors C1 and C2 (C2 is not present on some supplies), rectifier assemblies D1 and D2, fuse F1, capacitors C3 and C4, the PC board and capacitor C5.[8] The logic manual's sheet 440 draws the circuit, without values. C1 and C2, with R1 across them, smooth the +5 V output of rectifiers D1 and D2 ahead of 10 A fuse F1; on supplies without C2, F1 is 8 A. C3 and R2 do the same for +24 V (D3 and D4, 5 A fuse F2), and C4 and R3 for −5 V (D5 and D6, 1 A fuse F3). C5 is wired to terminals 5 and 6 of the transformer terminal block TB1.[9] The 5114 AC box holds relay R1, power connector J4, connector J3, fuse F4 and the line filter.[10]
The parts catalogue's power supply list (figure 13) gives:[11]
| Part | IBM part number |
|---|---|
| Power supply assembly | 4176540 (110–115 V 60 Hz), 4176555 (220–235 V 50 Hz) |
| Capacitor (two fitted) | 5252526 |
| Capacitor, where only one is fitted | 5616823 |
| Bar (not used with one capacitor) | 2572196 |
| Capacitors | 5261370, 5213837 |
| Capacitor | 5252868 |
| Transformer | 4176544 (60 Hz), 4176557 (50 Hz) |
| PC board assembly | 4176545 |
| Rectifier assembly | 5565062 |
| Resistor | 589764 |
| Fuse | 218794, or 122641 where only one capacitor is fitted |
| Fuses F2, F3 | 855251, 855253 |
The catalogue does not tie these part numbers to designators, and gives no capacitance or voltage for any of them. A supply with a single capacitor in place of the pair is a factory variant with its own fuse.[11][9]
Getting real values
[edit | edit source]Read the values printed on the parts, photograph every board before removing anything, and record designator, value, voltage, type and lead spacing. Measure capacitance and ESR out of circuit rather than replacing on age alone. The same method is set out on the 5100 guide.
Do not use values from the IBM PC family (5150, 5155, 5160, 5170). Those machines have no +8.5 V or +24 V rail and no ferroresonant supply.
When to recap
[edit | edit source]- A capacitor that is bulged, vented or leaking.
- A rail outside its published range on either unit.
- Ripple above IBM's limits on the 5114.
- A 5110 supply that trips its protection with no card fault found.
See Capacitor Failure Symptoms, and the replacement practice on the 5100 guide.
Related pages
[edit | edit source]- IBM 5110, IBM 5110 Maintenance Guide, IBM 5110 Troubleshooting Guide
- IBM 5110 Maintenance Information Manual, IBM 5110 System Logic Manual, IBM 5114 Diskette Unit Maintenance Information, IBM 5114 Diskette Unit Parts Catalog
- IBM 5100 Capacitor Replacement Guide, IBM 5120 Capacitor Replacement Guide
- CRT Discharge Procedure, Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 IBM, IBM 5110 Computer Maintenance Information Manual, SY31-0550-2 (February 1979), p. 3-42, "Power Supply PC Board", "Power Supply Protection" and "Reference Voltage"; p. 2-44, item 272, tolerance table. Hosted as IBM 5110 Maintenance Information Manual.
- ↑ 2.0 2.1 2.2 2.3 IBM, IBM 5110 System Logic Manual, SY31-0552-3 (February 1979), sheet 480 "5110/5114 D.C. Power Distribution". Hosted as IBM 5110 System Logic Manual.
- ↑ IBM 5110 MIM, p. 2-10, item 207 "AC Box".
- ↑ IBM 5110 MIM, p. 2-6, item 203 "Tape Unit".
- ↑ IBM, IBM 5110 System Maintenance Analysis Procedures, SY31-0553-2, third edition (January 1979), Tape Read MAP 0300, p. 0300-19, steps 189 to 192. Hosted as File:IBM 5110 System Maintenance Analysis Procedures SY31-0553-2.pdf.
- ↑ IBM 5110 MIM, p. 4-77, "AC Power Grounding Checks".
- ↑ 7.0 7.1 7.2 IBM, IBM 5114 Diskette Unit Maintenance Information, SY31-0551-1 (January 1979), p. 3-39, "Power". Hosted as IBM 5114 Diskette Unit Maintenance Information.
- ↑ IBM 5114 MI, p. 2-10, item 104 "Power Supply".
- ↑ 9.0 9.1 IBM 5110 System Logic Manual, sheet 440 "5114 Diskette Unit": 5114 power supply circuit and note 10.
- ↑ IBM 5114 MI, p. 2-11, item 105 "AC Box".
- ↑ 11.0 11.1 IBM, IBM 5114 Diskette Unit Parts Catalog, S131-0626-1 (September 1978), figure 13 "Power Supply Assembly", p. 29. Hosted as IBM 5114 Diskette Unit Parts Catalog.