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IBM System/23 Datamaster Maintenance Guide

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Revision as of 23:05, 30 September 2026 by Josh (talk | contribs) (Link the newly hosted 5324 Computer Service Manual (SY34-0241-1))
IBM System/23 Datamaster 5322

This guide covers maintenance of the IBM System/23 Datamaster 5322, the one-piece desk-top unit with a built-in display, keyboard and up to two 8-inch diskette drives. It follows IBM's 5322 Computer Service Manual (SY34-0171-0) and Diagnostic User Guide (PN 6841631). The floor-standing 5324 has its own service manual, SY34-0241-1 (May 1982), hosted here.[1]

⚠️ Safety

IBM's DANGER notice: up to 800 V AC is generated in the power supply. Before removing the supply or any part of it, switch off the 5322 and disconnect the power cable from the outlet.[2]

  1. Switch off and unplug the 5322 before removing any cover.
  2. The power supply slides out of the rear into a service position. To switch on with the supply in that position, IBM first has the engineer check grounding continuity between the 5322 main base plate and the power supply frame with the meter on the ohms RX1 range.[2]
  3. Follow the CRT Discharge Procedure before working near the display unit.
  4. Each diskette drive has an AC drive motor with a capacitor. IBM warns that high voltage may be present at the capacitor terminals and discharges it by shorting the terminals with an insulated screwdriver before disconnecting the motor leads.[3]

See also Recommended Tools and Battery Explosion, Capacitor or Corrosion Damage.

Documentation

  • IBM 5322 Computer Service Manual, SY34-0171-0 (December 1980): locations, removal and adjustment procedures, theory of operation and parts catalogue for the 5322, its power supplies, keyboard, display and internal diskette drives. Hosted here.
  • IBM System 23 Diagnostic User Guide, PN 6841631 (April 1982): the power-on test (PID 1200), the ROS-resident diskette test (PID 1500) and the diskette-resident diagnostic and utility programs. Hosted here.
  • IBM 5324 Computer Service Manual, SY34-0241-1, Second Edition (May 1982): the same structure for the floor-standing 5324. Hosted here.
  • On bitsavers: the 5324 maintenance analysis procedures, the August 1981 edition of the Diagnostic User Guide and the 5247 Disk Unit Service Manual (SY34-0243-0).[1]

IBM's own tool list for the System/23 is the CE meter (PN 1749231), the GLP II logic probe (453212), the metric tool kit (1749235), a plastic CRT adjustment screwdriver (460811), and at branch level a ROS module puller (1715889), a module pin aligning tool (453473), a ground check tool (9900453) and a Tektronix 465 or equivalent oscilloscope.[4] The ripple check below also needs a 0.22 µF, 50 V capacitor.

Opening the 5322

IBM's cover procedures (item 1220):[5]

  • Rear access cover: pull it toward the rear until the pressure latches release.
  • Top cover: remove the rear access cover and two screws, then pull the top cover toward the rear to free the front locating tabs.
  • Keyboard cover: remove two screws, lift the front edge and pull it forward.
  • Front cover: remove the rear access, top and keyboard covers and the keyboard (item 1330), put the power supply and planar board in their service positions, pull off the brightness knob (it is keyed to its shaft), turn the diskette latches horizontal, then remove five screws from the main support plate and centre bracket and 11 screws from the bottom cover.

CPU planar board drawer

The CPU planar board sits in a drawer at the rear. Remove the rear access cover, take the I/O cables out of the ground clamp, remove the two screws at the rear of the drawer and slide it out to its service position. In that position the attachment cards, cables, CE test pins and feature jumper pins are accessible. When a planar board is replaced, move each feature jumper to the same position on the new board, and afterwards check the display's horizontal centering adjustment (item 1440).[6]

Power supply

Remove the rear access cover and top cover, open the ground clamp and take out the I/O cables, remove the two screws at the rear of the supply and slide it out. The fuses, voltage test points and power switch can be reached in this service position. To remove the supply completely, unplug P1 to P5 and the diskette attachment cable voltage wires, and replace any cable ties that had to be cut.[2]

Planar board jumpers and storage

The CPU planar diagram shows these jumper positions:[6]

  • A1: CE loop on test. A2: CE stop on error. A3: machine update card installed.
  • B1 to B5: country select. C2: internal diskette not installed. A separate jumper is fitted on 50 Hz machines only.
  • IBM warns that other jumper pins on the planar are for manufacturing use and are not jumpered in normal operation.

Read/write storage is on one or two cards in the base and feature sockets. The base socket is always used.[6]

5322 storage cards and 64K card jumpers (SM p. 2-17)
Total storage Feature socket Base socket 64K card jumpers
32K - 32K -
64K 32K 32K -
64K - 64K 1 and 3
96K 32K 64K 2 and 4
128K 64K 64K 2 and 4

The power-on test checks storage in 16K blocks as routines 2A to 30. Routines 2A, 2D and 2E cover the base socket and 2B, 2C, 2F and 30 the feature socket.[7]

Power supply checks

A 5322 has either a ferroresonant supply or a transistor-switching-regulator (TSR) supply; IBM describes them as functionally interchangeable. Both give -5, +5, -12, +12 and +24 V DC and 120 V AC for the diskette motors, display and fan. The power-good LED, visible from the rear of the supply, is lit when -5, +5, -12 and +12 V are within about 80 % of nominal.[8]

Measure at the power supply A1 card, where IBM's tolerances apply:[9]

IBM 5322 DC outputs: tolerance, ripple limit and fuse
Output Tolerance Ripple, peak to peak Fuse
+5 V +4.6 to +5.5 V 0.12 V F5, 10 A
-5 V -4.6 to -5.5 V 0.05 V F1, 0.5 A
+12 V +11.0 to +13.2 V 0.175 V F2, 1.5 A
-12 V -11.0 to -13.2 V 0.12 V F3, 0.5 A
+24 V +22.0 to +26.4 V 0.325 V F4, 1.5 A
Power good +2.4 to +5.5 V 0 -

To check ripple without an oscilloscope, put a capacitor of 0.22 µF or more (50 V DC or higher) in series with one lead of the meter, set the 2.5 V AC range, and connect between the output and frame ground. If the pointer moves off zero, excess ripple may be present.[9]

The five fuse ratings are the same on all three documented supplies. IBM checks a fuse for continuity on the ohms RX1 range and warns never to fit one of a higher rating.[10] The US and Canada supply has AC input fuse F6, 5 A slow-blow;[11] the GBG/I supplies have circuit breaker CB1 instead.[8]

Mains voltage taps

The three documented supplies are PN 6838279 (60 Hz, Canada and US), PN 6838280 (60 Hz, GBG/I) and PN 6838281 (50 Hz, GBG/I). The two GBG/I supplies are set for the local mains by the line connection and jumpers on the transformer terminal board T1/TB; IBM's diagrams show both wired for 220 V. To change the setting, measure the outlet voltage, put the supply in the service position and rewire T1/TB from the chart. For a supply with a different part number, IBM says to follow the labels on the supply.[12]

T1/TB settings, GBG/I supplies (SM pp. 2-9, 2-10)
Mains PN 6838280 (60 Hz) line PN 6838280 jumpers PN 6838281 (50 Hz) line PN 6838281 jumpers
100 V 1-7 1-6, 2-7, 4-9 1-6 1-5, 2-6, 4-8
110 V 1-8 1-6, 3-8, 4-9 1-7 1-5, 3-7, 4-8
120 V 1-9 1-6, 4-9 - -
127 V 1-10 1-6, 5-10, 4-9 - -
200/208 V 1-7 2-6 1-6 (200 V) 2-5
220 V 1-8 3-6 1-7 3-5
230 V - - 1-8 3-5
240 V 1-9 4-6 1-8 4-5

Display

The CRT display unit has a 305 mm (12 in.) screen showing 24 lines of 80 characters. IBM warns against running the 5322 with the brightness control fully clockwise for long periods, because the screen could be damaged.[13]

Diskette drives

The internal drives are the 31SD (one read/write head) and the 51TD (two heads); they differ only in the head/carriage assembly and the drive control card. IBM's maintenance preface says:[14]

  • There is no preventive maintenance for the diskette drive. Repairs are adjustments and FRU replacements directed by the MAPs, verified with the diagnostics.
  • The head/carriage assembly can be replaced in the field, but "do not repair or clean any part of this assembly".
  • The drive hub and pulley assembly is adjusted at the factory and is not field-replaceable; if it or the track 40 adjustment surface is damaged, replace the whole drive.
  • Keep television sets, display terminals and other electromagnetic devices at least 0.61 m (2 ft) from the 5322.

The drive motor turns the hub through a belt (item 1552). When refitting the motor fan and pulley, IBM sets a 0.5 mm (0.020 in.) gap between the motor and the fan hub, with the setscrew on the flat of the shaft, and fits the fan enclosure so the belt sits in its recess.[15]

On the 31SD, the head load arm carries a pressure pad. IBM replaces it when it has worn level with the arm, using kit 2200751 (which includes pad tool 2200750). Old adhesive is cleaned off the arm's mounting surface with tissue moistened with isopropyl alcohol; the head itself is not cleaned. IBM warns not to touch the pad surface or let the arm hit the read/write head.[16]

Diskettes should be kept at 10 to 51 °C and 8 to 80 % relative humidity, stored flat in their envelopes in stacks of up to ten, and kept away from heat and sunlight.[17]

Keyboard

The keyboard has 83 keys over a capacitive matrix, scanned by a microprocessor on the keyboard card, which sends a scan code and an interrupt request to the processing unit. The complete keyboard assembly is one field-replaceable unit.[18] At power-on, routine 35 resets the keyboard; its processor runs its own test and replies X'2A55', or X'552A' if the test failed.[19]

References

  1. ↑ 1.0 1.1 bitsavers, ibm/system23/fe (retrieved 2026-09-30): SY34-0171-0 5322 Computer Service Manual, SY34-0241-1 5324 Computer Service Manual (May 1982), Diagnostic User Guide 6841631 (August 1981 and April 1982 editions), 5324 MAPs; and ibm/system23/5247: SY34-0243-0 5247 Disk Unit Service Manual (April 1982).
  2. ↑ 2.0 2.1 2.2 IBM, IBM 5322 Computer Service Manual, SY34-0171-0 (December 1980), item 1240, p. 2-21, power supply removal and replacement (hosted here).
  3. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1551, p. 5-40.
  4. ↑ IBM, Diagnostic User Guide 0001, System/23 with Diskette, PN 6841631, EC 327594 (April 1982), section 11, pp. 17-18 (hosted here).
  5. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1220, p. 2-14, covers.
  6. ↑ 6.0 6.1 6.2 IBM 5322 Computer Service Manual, SY34-0171-0, item 1230, pp. 2-16 and 2-17, CPU planar board removal, replacement and diagram.
  7. ↑ IBM, Diagnostic User Guide 0001, PN 6841631, section 21.4.1.11, p. 79.
  8. ↑ 8.0 8.1 IBM 5322 Computer Service Manual, SY34-0171-0, p. 2-57, "Power supplies".
  9. ↑ 9.0 9.1 IBM 5322 Computer Service Manual, SY34-0171-0, item 1211, p. 2-11, DC voltage distribution diagram.
  10. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, items 1241 (p. 2-22), 1251 (p. 2-29) and 1261 (p. 2-35).
  11. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1241, p. 2-23.
  12. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1210, pp. 2-9 and 2-10 (AC voltage charts), and items 1250 and 1260, pp. 2-28 and 2-34 (AC line voltage selection).
  13. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, pp. 2-41 (standard features) and 2-43 (operator controls).
  14. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 5-3, maintenance preface.
  15. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1552, p. 5-41.
  16. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1531, p. 5-29.
  17. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, pp. 5-62 and 5-63, diskette handling.
  18. ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 3-16, keyboard data flow.
  19. ↑ IBM, Diagnostic User Guide 0001, PN 6841631, section 21.4.1.16, p. 80.


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