IBM PC XT/370 Maintenance Guide
The IBM PC XT/370 is an IBM PC XT (5160) with System/370 processor and memory cards, so most of its maintenance is the XT's: see the IBM PC XT Maintenance Guide. The points below are specific to the XT/370: the cards and their slots, the memory settings, and the 20 MB configuration with its separate expansion unit.
Safety
[edit | edit source]The system unit supply is the standard 5160 unit: a 130 W switching supply, in separate 120 V and 220/240 V versions, both fused.[1] Turning off its red switch does not remove mains voltage from everything inside it, and its primary capacitors can hold a dangerous charge after it is unplugged; measure them before touching anything.[2]
A 20 MB XT/370 has its fixed disks in a 5161 Expansion Unit, which is a second mains-powered box with its own 130 W XT supply. Isolate it as well.[1] For the display, follow the CRT Discharge Procedure.
Documentation
[edit | edit source]- IBM Personal Computer Family Service Information Manual: IBM's 1989 service manual. Chapter 6 covers the 5160 and the XT/370, chapter 7 the 5161, chapter 18 the parts.[1]
- IBM PC XT 5155 5160 Technical Reference (March 1986): the XT system board and power supply.[3]
- VM/PC User's Guide (December 1984), for the VM/PC software.
Opening the system unit
[edit | edit source]- Switch off and disconnect the mains lead, keyboard, display, printer and the coaxial cable to the control unit.
- Remove the five system cover screws; IBM's parts catalogue lists "Screw, System Cover (Qty 5)".[4]
- Slide the cover forward. Some drive screws are reached through a well in the underside of the case.[5]
The XT/370 cards
[edit | edit source]IBM fixes the card positions:[1]
| Card | IBM FRU | Slot |
|---|---|---|
| PC/370-P processor card | 8654372 | 4 |
| PC/370-M 512 KB memory card | 8654371 | 3 |
| PC/370-P-M cable (between the two cards) | 8654374 | |
| PC/3277-EM terminal emulation card (models 568 and 588) | 8654373 | |
| Remote Display Terminal Device Emulation Adapter (option) | May be in slot 2 | |
| IBM 3278/79 Emulation Adapter (option) | 8654378 |
The processor and memory cards are joined by their own cable, so take them out and refit them together. The rest of the slots hold the usual XT cards: diskette adapter, fixed disk adapter and display adapter.
The host link is coaxial cable to a 3274 control unit.[6] IBM's cable checks for the 3270 family are in the 3270 PC maintenance guide.
IBM's service manual gives no component-level data for any of the XT/370 cards; it treats them as field-replaceable units.[1] See IBM PC XT/370 Capacitor Replacement Guide.
Memory settings
[edit | edit source]- The XT/370 needs 256 KB on the system board; the PC/370-M card supplies the rest of the 640 KB the PC side sees.[1][7]
- On the 20 MB XT/370, IBM specifies that the extender card switches be set for 608 KB to 640 KB.[1]
- IBM's decoding of a 201 memory error on the 64/256 KB system board used in the XT/370 is in the XT troubleshooting guide.
Power supply checks
[edit | edit source]Measure with the supply connected to the system board. IBM's limits at the board connectors, and the Technical Reference load range and sense levels:[8][3]
| Rail | Maximum load | Service limits | Sense level for power good |
|---|---|---|---|
| +5 V | 15 A | +4.8 to +5.25 V | +4.5 V |
| −5 V | 0.3 A | −4.6 to −5.5 V | −4.3 V |
| +12 V | 4.2 A | +11.5 to +12.6 V | +10.8 V |
| −12 V | 0.25 A | −10.9 to −13.2 V | −10.2 V |
The system board takes about 2 to 4 A of the +5 V, leaving about 11 A for the cards.[3] The supply shuts all outputs down on a DC overcurrent or overvoltage and stays down until the fault is removed, so a dead machine with good fuses usually has a short on the board or a card; remove cards one at a time to find it.[3] Leave at least one second between switching off and on.[3] Pin numbers and the dummy load for an unconnected supply are in the XT maintenance guide.
Drives
[edit | edit source]- The Model 588 has one 10 MB fixed disk in the system unit; the 20 MB configuration uses a Model 568 with two fixed disks in a 5161 Expansion Unit.[1][7]
- Before moving the machine, run the advanced diagnostics option "Prepare Fixed Disk for Relocation" to park the heads.[9]
- Do not clean the diskette heads by hand; Tandon's manual for the TM100 drives forbids it.[10] Belt, speed and rail notes are in the XT maintenance guide.
VM/PC files
[edit | edit source]VM/PC keeps each CMS minidisk as a DOS file named after the owner and minidisk address, for example C:CMS.100, and IBM's guide says minidisks can be backed up with any DOS backup method.[11] Copy them off before working on the fixed disk.
Keyboard
[edit | edit source]The XT/370 uses the 83-key keyboard.[1] See foam sheet repair for dead or twisting keys.
Related pages
[edit | edit source]- IBM PC XT/370
- IBM PC XT/370 Troubleshooting Guide
- IBM PC XT/370 Capacitor Replacement Guide
- IBM PC XT Maintenance Guide
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 IBM, Personal Computer Family Service Information Manual, SA38-0037-00, First Edition, January 1989, hosted as File:IBM Personal Computer Family Service Information Manual SA38-0037-00.pdf. Chapter 6: 5160 power supply (p. 6-2); extender card switch settings (p. 6-14); "5160 XT/370" (pp. 6-17 to 6-19). Chapter 7: 5161 Expansion Unit (p. 7-1). Chapter 18: XT/370 parts (p. 18-19).
- ↑ IBM 5160 – Power Supply Unit, minuszerodegrees.net, and IBM 51xx PC Family Computers – Some Hazards Within.
- ↑ 3.0 3.1 3.2 3.3 3.4 IBM, Personal Computer XT and Portable Personal Computer Technical Reference, part 6139821, March 1986, hosted as File:IBM PC XT 5155 5160 Technical Reference Mar86.pdf. Section 3: supply outputs, load range, sense levels, fuses and power good (pp. 3-3 to 3-5).
- ↑ IBM, Hardware Maintenance Service parts catalogue, part 6280087 (PC, XT and Portable PC), p. 12, hosted as File:IBM Hardware Maintenance Service 6280087 Parts Catalog (PC, XT, Portable PC).pdf.
- ↑ IBM 5160 – Basics, for 5160 beginners, minuszerodegrees.net.
- ↑ "IBM Personal Computer XT/370", in "IBM Personal Computers at a Glance", BYTE Guide to the IBM PC, Fall 1984, p. 19 (archive.org item byte-magazine-1984-09).
- ↑ 7.0 7.1 Ernest Sabine, "The IBM XT/370 Personal Computer", BYTE Guide to the IBM PC, Fall 1984, pp. 210–211: the 256 KB requirement for conversion, and the PC/370-M memory mapping.
- ↑ IBM, Personal Computer Family Service Information Manual, SA38-0037-00 (1989), chapter 4, p. 4-3, Figure 4-5, and p. 4-4 (dummy load).
- ↑ IBM, Personal Computer Family Service Information Manual, SA38-0037-00 (1989), chapter 4, p. 4-11.
- ↑ Tandon, TM100-1 / TM100-2 48 TPI Operating and Service Manuals (1983), p. 6-1, hosted as File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf.
- ↑ IBM, Virtual Machine/Personal Computer User's Guide, December 1984, hosted as File:IBM VM-PC User's Guide (December 1984).pdf: minidisk file names (p. 3-18) and backing up minidisks (p. C-1).