IBM System/23 Datamaster Troubleshooting Guide
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This guide covers fault diagnosis on the IBM System/23 Datamaster 5322 using IBM's own diagnostics: the power-on test in read-only storage (PID 1200), the ROS-resident diskette test (PID 1500) and the programs on the CE diagnostic diskette. All three are described in IBM's Diagnostic User Guide (PN 6841631); the locations, fuses and voltages they refer to are in the IBM 5322 Computer Service Manual (SY34-0171-0).
First checks
[edit | edit source]| Symptom | Probable cause | Action |
|---|---|---|
| Nothing at all | No mains, AC input fuse or breaker | On the US and Canada supply check F6 (5 A slow-blow); GBG/I supplies have circuit breaker CB1 instead.[1] |
| Power-good LED off | A DC output below about 80 % of nominal | The LED, visible from the rear of the supply, is lit only when -5, +5, -12 and +12 V are all up.[2] Check F1 to F5 and measure each output at the A1 card (table below). |
| Imported machine, wrong or no output | Mains taps set for another voltage | GBG/I supplies are set on transformer terminal board T1/TB; see the charts in the Maintenance Guide.[3] |
| Screen stays blank for half a minute | Normal | The power-on test takes 25 to 35 seconds, depending on configuration.[4] |
IBM's DANGER notice: up to 800 V AC is generated in the power supply. Switch off and unplug the 5322 before removing the supply or any part of it.[5]
Measure at the power supply A1 card, where IBM's tolerances apply:[6][7]
| 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 | - |
IBM checks fuses for continuity on the ohms RX1 range and warns never to fit one of a higher rating.[7] Its ripple check without an oscilloscope is described in the Capacitor Replacement Guide.[6]
The power-on test (PID 1200)
[edit | edit source]PID 1200 is held in read-only storage (ROS) and runs at every power-on and whenever a program branches to location 0000.[4] If it finds no errors, the 5322 enters BASIC and shows "READY INPUT".[8]
How errors are reported
[edit | edit source]Routines 01 to 06 run before the display is started. An error there stops the machine and leaves an error code in a set of hardware latches, which the customer engineer reads with a logic probe on the CE register test pins of the CPU planar board (SM 1230; IBM's MAP 1100 covers probe set-up).[4][9] Once the display is running, the latch contents are shown on screen and the attribute of each routine number gives its result:[4]
| Attribute | Meaning |
|---|---|
| Normal | The routine ran without error. |
| Flashing reverse video | Error in a part critical to system operation. The system stops after finishing the power-on sequence. |
| Reverse video | Error in a part that is not critical. Pressing ERROR RESET lets initialisation continue. |
| Underline | The feature that routine tests is not installed. This is not a fault. |
If a TRAP occurs during the test, the failure is in the routine after the last one displayed.[4]
Two jumpers on the CPU planar board select test options: A1 loops the test until the jumper is removed, and A2 stops the machine after an error is displayed. IBM says to disconnect the external diskette attachment cable before looping, and to fit the stop-on-error jumper whenever the loop jumper is fitted and the machine is left unattended.[4][9] Check that neither is fitted on a machine that appears to be stuck.
Routines
[edit | edit source]| Routine | Area tested | Critical | Notes |
|---|---|---|---|
| 01 | CPU and data bus | Yes | Address and data bus check; CPU flags and registers. |
| 02 | ROS | Yes | CRC check of the first ROS module, which holds the test itself. |
| 03 | Reserved | Yes | |
| 04 | Read/write storage | Yes | First 16K of standard storage. |
| 05-07 | CRT controller | Yes | 06 and 07 test the horizontal, vertical and video lines; a general logic probe on the CRT connector verifies the drive circuits. |
| 08 | Page registers | Yes | Basic test of ROS, read/write storage and DMA page registers. |
| 09-19 | ROS on the planar board | Yes | CRC test. |
| 1A-29 | Feature ROS on I/O cards | Yes | CRC test. |
| 2A-30 | Read/write storage | Yes | 16K blocks up to 128K. 2A, 2D and 2E are in the base socket; 2B, 2C, 2F and 30 in the feature socket. |
| 31 | Storage page register | Yes | |
| 32 | DMA page register | Yes | |
| 33 | Interrupt controller | Yes | A hot interrupt stops the test and its number is shown on the fourth line (see below). |
| 34 | Interval timer | Yes | |
| 35 | Keyboard | Yes | See Keyboard. |
| 36, 37 | Printer attachment and printer diagnose command | No | Skipped if no printer cable is sensed. |
| 38 | Diskette attachment | No | Does not need a diskette in the drive. |
| 39 | +24 V to the internal diskette drives | No | Check fuse F4 first. |
| 3A, 3B | Second printer attachment (feature) | No | |
| 3C | Internal wrap of the serial interface adapter | No | If it fails, 3D and 3E are bypassed. |
| 3D, 3E | Link to a 5247 disk unit, and 5247 ready status | No | Status bytes are shown after the routine number. |
| FD | System diskette initialisation | - | See below. |
Routine 33 reports the interrupt that stayed active: 1 keyboard, 2 printer receive, 3 printer transmit, 4 printer 2 receive, 5 diskette, 6 printer 2 transmit, 7 TP receive, 8 TP transmit.[10]
FD is shown at the end of the test while system diskette initialisation is in progress. If the test hangs with FD as the last routine and no reverse-video errors, IBM says the initialisation could not be completed, usually because an external diskette could not be accessed; the cause is either a hardware failure or an external diskette unit being used in shared mode by another processor.[10]
Keyboard
[edit | edit source]Routine 35 resets the keyboard. The keyboard's own processor runs a diagnostic and replies X'2A55'. It replies X'552A' if its diagnostic failed; any other two characters returned are printed on the fourth line of the screen. If a key is held or stuck, its scan code is shown there instead.[10] The complete keyboard assembly is a single field-replaceable unit.[11] The keyboard fault-location test is PID 1300 on the CE diagnostic diskette.[12]
Machine checks (TRAP)
[edit | edit source]When a machine check occurs while a BASIC program or a diagnostic is running, the 5322 shows a line of TRAP data at the bottom of the screen, starting with the trap class. IBM interprets it with MAP 1220.[13]
| Class | Meaning |
|---|---|
| 80xx | Power check |
| 40xx | Write to ROS |
| 20xx | I/O channel |
| 10xx | Storage parity check |
| 00xx | System programming error |
The rest of the line gives the page in use, the interrupt masks, the storage, ROS and DMA page registers, the processor register contents, the program counter and the stack contents at the time of the trap.[13]
Diskette drives (PID 1500)
[edit | edit source]PID 1500 tests the diskette attachment card and the read path to drives 1 to 4. After the power-on test finishes, hold CMD and press TEST, then hold CMD and press ERROR RESET. Insert the CE diagnostic diskette before selecting a drive. The menu offers, one line at a time: select drive, run the diagnostic (routines 01 to 0A), loop it, the map chart routine, and load the diagnostic control program (DCP). Press 9 on the numeric keypad to end.[14]
Failures are shown as "ROUTINE xx ENDING STATUS yy zz". Some of the stop IDs:[14]
| ID | Meaning | ID | Meaning |
|---|---|---|---|
| 03 | VFO did not go in sync | 12 | Seek error |
| 08 | Diskette controller did not respond | 16 / 17 | Rotational speed too slow / too fast |
| 09 | Diskette not ready | 1C | Missing index pulses |
| 0A | Could not select a diskette | 32 | Could not secure external drive |
| 0D | CRC error | F6 | Missing address marks |
| 0F | No record found | FB | DCP not found on diskette |
| 10 | Missing 24 V to diskette | FF | Good ending sequence |
Routine 06 checks the index pulse: width 1.5 to 3.0 ms, and 166 ± 4.2 ms from one index pulse to the next. Routine 01 restarts the attachment card's microcontroller, which answers 'AA','55' when its internal diagnostic passes.[14] The map chart routine lets the engineer recalibrate, step in or out one or four tracks, and run a head alignment sequence (track 40, 39, 40) for the service manual's head/carriage adjustment.[14] IBM's maintenance preface says there is no preventive maintenance for the drive and that no part of the head/carriage assembly is to be repaired or cleaned.[15]
CE diagnostic diskette
[edit | edit source]The diskette-resident programs are on CE diagnostic diskette PN 6841645 (PN 6842304 for systems with a 5247). They are reached through the DCP, loaded from PID 1500. The DCP menu includes the diskette fault-location tests (PID 1505 and 1510), keyboard (PID 1300), 5241/5242 printer (PID 2300), CPU processor (PID 1205), CPU storage (PID 1210), communications (PID 5000), screen test patterns (PID 1400) and, with the work station adapter installed, the 5247 tests. The CE utility menu includes diskette format, copy and read/verify, and the error log display (PID 0120), which shows the soft errors and read/write counts the system has logged for each diskette.[12][16]
Related pages
[edit | edit source]- IBM System/23 Datamaster, IBM System/23 Datamaster Maintenance Guide, IBM System/23 Datamaster Capacitor Replacement Guide
- IBM 5322 Computer Service Manual and IBM System 23 Diagnostic User Guide, both hosted here
- IBM PC (5150) Troubleshooting Guide
References
[edit | edit source]- ↑ IBM, IBM 5322 Computer Service Manual, SY34-0171-0 (December 1980), p. 2-23 (F6) and p. 2-57 (CB1) (hosted here).
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 2-57, "Power supplies".
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, pp. 2-9 and 2-10.
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 IBM, Diagnostic User Guide 0001, System/23 with Diskette, PN 6841631, EC 327594 (April 1982), section 21, pp. 75-76, "PID 1200 (Processor power-on test)" (hosted here).
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, item 1240, p. 2-21.
- ↑ 6.0 6.1 IBM 5322 Computer Service Manual, SY34-0171-0, item 1211, p. 2-11, DC voltage distribution diagram.
- ↑ 7.0 7.1 IBM 5322 Computer Service Manual, SY34-0171-0, items 1241 (p. 2-22), 1251 (p. 2-29) and 1261 (p. 2-35).
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 2-43, operator switches and controls.
- ↑ 9.0 9.1 IBM 5322 Computer Service Manual, SY34-0171-0, item 1230, pp. 2-17 and 2-18 (CPU planar board diagram: CE register test pins bit 0 to bit 7, CE logic probe power pins).
- ↑ 10.0 10.1 10.2 10.3 IBM, Diagnostic User Guide 0001, PN 6841631, sections 21.3 and 21.4, pp. 77-83.
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 3-16, keyboard data flow.
- ↑ 12.0 12.1 IBM, Diagnostic User Guide 0001, PN 6841631, sections 1.0 to 3.1, pp. 1-4.
- ↑ 13.0 13.1 IBM, Diagnostic User Guide 0001, PN 6841631, section 9.0, p. 15, "Trap data".
- ↑ 14.0 14.1 14.2 14.3 IBM, Diagnostic User Guide 0001, PN 6841631, section 28, pp. 115-122, "PID 1500 (ROS resident diskette drive 1-4 test)".
- ↑ IBM 5322 Computer Service Manual, SY34-0171-0, p. 5-3, maintenance preface.
- ↑ IBM, Diagnostic User Guide 0001, PN 6841631, section 18, p. 49, "PID 0120 (Error log display utility)".