IBM 5110 Troubleshooting Guide

IBM 5110 (Wikimedia Commons)

Fault finding on the IBM 5110 Computing System uses IBM's System Maintenance Analysis Procedures (MAPs), SY31-0553-2, and the Computer Maintenance Information Manual (MIM), SY31-0550-2. The 5110 reports faults through the PROCESS CHECK light, the bring up diagnostic's letter display, and error messages on the screen; error messages appear only when enough of the machine works for them to be accurate.

Rail tolerances, the meter check, the bring up halt table and the tape status byte are on the IBM 5110 Maintenance Guide.

Where to start

Every call starts at the start MAP (0200). IBM's failure isolation chart sends intermittent process checks to the Free Lance Troubleshooting Guide in the MIM, operator and program errors to the customer error code descriptions, and bring up failures to the bring up diagnostic chart for card swapping. The MAPs are:

IBM 5110 MAPs (SY31-0553-2)

MAP	Covers
0200	Start
0210	Cable checkout
0300	Tape read
0310	Diskette read
0400	Bring up
0420	Process check
0500	Display
0510	TV monitor
0600	Keyboard
0700	Power
0810	5103 printer
0830 to 0838	Communications, serial I/O and parallel I/O, including BSC and modem procedures
0850	Auxiliary tape (5106)
0880	5114 Diskette Unit entry
0900	Machine checkout

Logic card part numbers by position and model are on MAP pp. 050-1 and 050-2.

ROS errors during bring up

If the bring up diagnostic stops at ABCDEFGHJKLMNP with ROS XX YY on the display, XX is the ROS module being tested and YY the module ID read. Modules 1X are the BASIC ROS on the common and language ROS card (F2); 2X, 31 and 32 are the APL ROS card (E4); 33 and 4X are on F2. If replacing the APL card does not cure a 2X, 31 or 32 failure, replace F2, which can cause an addressing fault. On a dual-language machine the bring up diagnostic tests only the language ROS selected by the BASIC-APL switch; switch languages and press RESTART to test the other.

The ERROR code shown with a ROS failure points at a card:

IBM 5110 ROS error codes (MIM p. 4-112)

Error	Card
001, 005	Common and language ROS (F2)
002, 014	Executable ROS (L2), processor (J2) or read/write storage (M2)
007	CRC error
008	Module ID error

Intermittent process checks

Leave the I/O cable connected and do not press RESTART. With PROCESS CHECK lit, probe these pins to find the error and the cards to suspect:

IBM 5110 process check probe points (MIM p. 4-76)

Error line	Pin	Cards
−RDR	J2S08	G2, J2, L2, M2, M4, N2, N4, A2
−Bus in	J2U09	A2, B2, D2, F2, H2, J2
+DA error, base I/O	H2M02	H2, J2
+DA error, common and language ROS	F2U13	F2
+DA error, display	G2M09	G2
+DA error, executable ROS	L2P06	L2
+DA error, parallel I/O	K2J06	K2
+DA error, async comm/serial I/O	D2J13	D2
+DA error, BSCA	B2J04	B2
+DA error, 5114	A1-C1D11 in the 5114	5114 A1-C1
+Bus out error, base I/O	H2P07	H2, J2, L2, A2, M2, M4, N2, N4
+Keyboard parity error	H2U13	H2

Then reseat all cards and cables, check the voltages, check the customer's AC ground and check the fans.

Tape errors

IBM's procedure for intermittent tape errors:

1. Cartridges written before a drive fault was fixed can still give errors.
2. Check the cartridge stops.
3. Do the tape select magnet service check.
4. Clean the head with isopropyl alcohol and a lint-free tissue, check the head adjustment, and replace a worn head.
5. Clean the spindle assembly and drive rolls with isopropyl alcohol and a lint-free tissue.
6. Check the cartridge-in-place and file protect switch adjustment.
7. Reseat the cables and cards in the tape unit.
8. Make sure the tape unit does not face strong light or sun.
9. Make sure the brake arms are the white ones, not the black ones.

The tape error codes (002 to 014) have the same meanings as on the 5100; see the 5100 guide. The latest tape status byte is at hex 8F.

Diskette errors

Selected 5114 error codes:

IBM 5110 diskette error codes, selected (MIM pp. 4-100 to 4-103)

Code	Meaning
025	Invalid media: the volume 1 label does not match the diskette type sensed
026	Head select failure: the ID read came from the other side of the diskette
027	Access failure: the head was repositioned ten times without finding the right cylinder
030	The drive cover was opened since the last command; a sense command must verify the new diskette first
032	Overrun on read or write
033	Head engage failure
034	Erase gate failure: tunnel erase did not switch on or off properly
045	No index: no index pulse for 333 ms, because no diskette is mounted or it is mounted backwards

For the 5114 itself, start at MAP 0880 and use the IBM 5114 Diskette Unit Maintenance Information. Its supply delivers +5, −5 and +24 V; ripple above 0.16 V peak to peak on ±5 V or 0.8 V on +24 V is out of limits, and the supply is protected by a fuse.

Printer errors

The 5103 error codes are on MIM pp. 4-103 and 4-104. Error 013 means the printer is not attached: an incorrect device address, or bus in returned hex FF. Error 051 means the printer's +24 V or 10.8 V is out of tolerance, or a wire check with the head at the left margin. A broken carrier belt can cause 057.

AC power and grounding

IBM's grounding check measures the outlet: neutral to ground should be under 2 V AC, and hot to neutral and hot to ground about 110 to 120 V AC on a 115 V supply. Line voltage should stay within ±10 %, apart from 500 ms transients of +15 % to −18 %. For a suspected line problem IBM suggests an isolation transformer, checking that line-side and load-side wires in the AC box do not cross, checking that the AC box capacitors are not twisted with their wires crossed, and looking for nearby equipment that induces noise. Ungrounded circuits cause intermittent failures, improper program operation and unreadable tapes or diskettes.

Related pages

• IBM 5110
• IBM 5110 Maintenance Guide
• IBM 5110 Capacitor Replacement Guide
• IBM 5100 Troubleshooting Guide