IBM PS/2 Model 80 Maintenance Guide

IBM PS/2 Model 80 (8580) system unit.

Routine maintenance on the IBM PS/2 Model 80 (machine type 8580) covers all three system boards: the 16 MHz and 20 MHz boards of 1987 and the 25 MHz board of 1990. The Model 80 uses the same tower case, side cover, front bezel, drive support structure and battery/speaker assembly as the IBM PS/2 Model 60 and Model 65 SX, and the same supply form factor and pinout.

Safety

The supply rectifies the mains and its reservoir capacitors hold a charge after the machine is unplugged. In the 225 W supply P/N 72X6665 there are two, C5 and C6, each 1000 µF 200 V, connected in series with a chain of 220 kΩ balancing resistors across each. Other makes of supply with the same IBM numbers are built differently. Unplug the machine before opening the case, and measure both capacitors before touching the primary side of an opened supply.

IBM gives the system unit's weight as up to 26 kg with options and says to service it standing upright; it can be laid on its side, without the cover, once the feet are folded in. IBM's lithium battery caution: do not recharge the pack, take it apart, heat it above 100 °C, burn it or expose the cell contents to water; replace it only with part 72X8498 or an equivalent.

There is no CRT in the system unit. IBM's displays have their own tube and supply; see CRT Discharge Procedure.

Opening the system unit

The side cover is held by two large captive screws.

1. Switch off and unplug the mains lead and all cables.
2. Turn the two large screws on the side cover anticlockwise with a coin or large flat blade until they are loose. They stay in the cover.
3. Swing the cover out on its bottom hinges until the top edge clears the case, then lift it up and out.

The cover lock is on the left side of the system unit. If the keys are lost, IBM's procedure is to order a new cover-lock assembly, which comes with two keys, and force the old lock with one of the new keys and a pair of pliers. Tony Ingenoso's method, on Ardent Tool, needs no new lock if the bottom slot is empty: turn the machine upside down, take off the front bezel, loosen the slot retainer, push the bottom slot cover into the case, and with a torch find the front and rear retaining tabs on the bottom of the side cover. Lever them down with a long thin screwdriver, from the rear through the slot opening and from the front through one of the bezel holes, shimming the first tab so it does not spring back. Ardent Tool's measurements from an 8580: the front tab is 2.8 inches from the front corner and the rear tab 3.6 inches from the back, both 1.5 inches in and about 0.25 inch deep, for anyone who drills small access holes instead.

Removing the front bezel

1. Open the side cover.
2. At the bottom front corner, pull the battery/speaker assembly out horizontally by its frame and lay it in the bottom of the case. Do not pull the battery lead off the system board, or the configuration is lost.
3. Press the white plastic catch below the grille down and towards the front. The second catch is behind the black foam round the grille; feel for the inner edge of the foam and push that catch down and forwards too.
4. With both catches pushed level with the case, pull the bottom edge of the bezel away. A third catch sits to the right of the power switch.

Power supply checks

The supply connects to the system board through a 15-pin connector and to the fixed-disk positions through two 4-pin connectors. It has three DC outputs, +5 V, +12 V and −12 V; there is no −5 V rail.

15-pin system board power connector

Pins	Signal
1, 4, 7, 10, 13	+5 V DC
2, 5, 6, 8, 11, 14	Ground
3	+12 V DC
9	−12 V DC
12	Power Good
15	System Status (fixed-disk activity light)

IBM's test is made with the black lead on pin 2. Unplug the 15-pin connector from the system board before measuring at a drive connector. If any voltage is outside these limits, or the supply fan is not running, IBM replaces the supply.

Models 60, 65 and 80: IBM supply test voltages

Leads	Rail	Minimum	Maximum
Pin 2 to pin 9	−12 V	−9.0 V	−15.0 V
Pin 2 to pin 3	+12 V	+9.0 V	+15.0 V
Pin 2 to pin 1	+5 V	+3.7 V	+6.2 V
Drive connector B to D	+5 V	+3.7 V	+6.2 V
Drive connector C to A	+12 V	+9.0 V	+15.0 V

These limits only decide whether IBM changes the supply. The supply raises Power Good, which lights the green lamp on the front, only when +5 V is above 4.5 V, +12 V above 10.8 V and −12 V beyond −10.2 V. The 1987 technical reference adds that Power Good comes up 100 to 500 ms after +5 V reaches its sense level and stays up for at least 10 ms after the mains is removed. A machine that runs with the green lamp off has a supply that is not meeting those levels.

The supply protects itself. A short between any two outputs, or from an output to DC return, latches every output off without damage, and an internal over-voltage fault latches them off before any output passes 130 % of nominal. The supply restarts only when the fault is gone and the switch has been off for a while: at least one second in the 1987 technical reference, ten seconds in the 1990 edition. A tower that clicks off and will not restart at once may simply be latched. The supply restarts by itself after a mains failure.

Before opening the supply of a dead machine, check the power switch. Peter Wendt reports that about half the failed Model 80 supplies he dealt with had a broken switch, the red ones more often than the white; the same switch was used in IBM 327x and 525x terminals and was available as a spare.

To remove the supply, take the rear drive carrier out of the drive support structure, unplug the 4-pin drive power leads and the system board power plug, remove the three screws holding the supply, and pull it out.

Power budget

Each 16-bit Micro Channel connector may draw 1.6 A at +5 V and each 32-bit connector 2.0 A, plus 0.175 A at +12 V and 0.040 A at −12 V; each fixed-disk power connector is rated at 1.5 A at +5 V and 2.5 A at +12 V. Fred Spencer's figures for the original drives are 31-39 W each for the 44, 70 and 115 MB drives, 35-42 W for the 314 MB, and 13-19 W for a 3.5-inch SCSI drive; citing IBM's Personal System/2 Reference Guide, he gives 7-10 W for an IBM 16-bit adapter and 7-13 W for a 32-bit one.

Battery and real-time clock

The clock is a Motorola MC146818A on the system board: U187 on the 16 MHz board, U186 on the 20 MHz board and U132 on the 25 MHz board, with a 32.768 kHz crystal. It holds 64 bytes of CMOS RAM (50 for configuration and security, 14 for the clock), and a separate 2 KB CMOS RAM extension holds more configuration data; the battery keeps both when the machine is off. The battery is a 6 V two-cell lithium pack, FRU 72X8498, in the battery/speaker assembly (FRU 33F5950 with its cable, 72X8511 without). The pack is sold as a camera battery: CR-P2, Duracell DL223A, Ever Ready EL223AP, Kodak K223LA or Ray-O-Vac PC223. On the Model 80 the assembly slides out towards the open side of the case.

Take the battery out of the assembly before unplugging the assembly's cable, and plug the cable in before refitting the battery, so the pack is not accidentally discharged.

Checking the battery

IBM retain tip H024809 names a low battery or a faulty battery/speaker assembly as causes of intermittent 161, 162 and 163 errors. Take the battery out of the assembly (a reading taken in place is not accurate), set the meter to a 12 V DC range, and replace the pack if it reads below 5.5 V.

A clock that stands still after long power-offs while the configuration survives is an early sign of a failing pack. Alfred Arnold's explanation on Ardent Tool: as the voltage falls, the RTC's 32 kHz oscillator stops first, while the CMOS RAM still holds, and 161 and 163 errors follow. After a 161 and 163, Peter Wendt notes that the first load of the Reference Diskette can take up to 90 seconds, and that on older Model 80 BIOS levels pressing F1 may be needed to force the load.

When the configuration has been lost, restore it from the user's backup Reference Diskette if the machine had custom settings, or run Automatic Configuration if it used the defaults.

Draining CMOS

Removing the battery and waiting for CMOS to drain can take hours. IBM retain tip H104756 gives a faster way: disconnect the battery, then with a meter lead connected to frame ground (the supply case will do) drag the lead round every pin of the two CMOS modules. Reconnect the battery afterwards.

CMOS module positions (retain tip H104756)

Models	Positions
-041, -071 (16 MHz)	U186 and U187
-081, -111, -121, -161, -311, -321 (20 MHz)	U146 and U186
-A16, -A21, -A31 (25 MHz)	U132 and U152 (near the blue connector)

Clearing a power-on password

1. Switch off and unplug the mains lead.
2. If the battery/speaker assembly has pins, short pins 2 and 3 together. If it has none, put a meter lead into connector 1 and hold the other end on frame ground.
3. Switch on with the short in place and keep it there until POST has finished. This removes the password.
4. To set a new one, start from the Reference Diskette and use Set Features.

Dust under the supply fan

The supply fan sits over a part of the system board that holds the 8042 keyboard controller, the MC146818A, the diskette controller, the NS16550 UART, the RTC crystal and sometimes an 8259A. Peter Wendt reports that household dust drawn in by the fan is often conductive, and that it causes lost configuration, a clock showing wrong values after long power-offs, and diskette or disk read/write errors that a new battery does not cure.

1. Strip the machine and blow the dust out of the supply with a compressor and a fine nozzle, somewhere that can get dirty.
2. Brush and vacuum the system board, looking for dust packed between IC pins.
3. Clean the diskette-controller area with a cotton bud and isopropyl alcohol.
4. Reassemble, start from the Reference Diskette, and set the date, time and configuration again.

Micro Channel adapters

The stored configuration depends on which slot each adapter is in. Refit a replacement adapter in the same slot; if it goes elsewhere, run Set Configuration from the Reference Diskette. After adding a card, start from the Reference Diskette with it in the drive at power-on, copy the card's option diskette so its adapter description file is available, and run Automatic Configuration.

Two limits from Ardent Tool: the 8580's Set Configuration program handles only 64 MB of memory, and the IBM SCSI-2 Fast/Wide adapter is not supported by the 8570 and 8580 BIOS (retain tip H125078).

Memory

System-board memory is on IBM memory cards in two connectors, J15 and J16 on the 16 MHz and 20 MHz boards and J8 and J9 on the 25 MHz board. They are not SIMM sockets. IBM gives the board capacity as 1 or 2 MB on the 16 MHz board, 2 or 4 MB on the 20 MHz board and 4 or 8 MB on the 25 MHz board, and the system total as 16 MB with 80386 memory expansion adapters in the 32-bit slots. Run Set Configuration whenever memory is added or removed.

IBM's procedures for the memory codes:

• 00011000, system-board parity check: if two kits are fitted, remove the one in J15 (or J8). If the error goes, replace that kit; if not, replace the kit in J16 (or J9); if that fails, replace the system board.
• 00011100, memory-adapter parity check: remove memory adapters one at a time until the error goes, then refit the kits on the last adapter removed one at a time until it returns, and replace that kit, then the adapter.
• 00021500: the kit in J15 (or J8), then the system board.
• 00021600 or 00022100: the kit in J16 (or J9), then the system board.

Advanced Diagnostics loads into the first 256 KB and cannot stress-test that area, so for an intermittent 110 parity error that the diagnostics do not find, IBM retain tip H006554 says to swap the two cards and run the memory test again. If POST finds an error in the first 512 KB it disables the first 1 MB block and moves its addresses to a second block if there is one; errors beyond the first megabyte are reported, and the customer diagnostics on the Reference Diskette disable the failing 1 MB block.

Ardent Tool records that the 8580 limits DMA to the first 16 MB, and that under Linux with more than 16 MB fitted the ibmmca SCSI driver needed its unchecked_isa_dma flag set.

Math coprocessor

The Model 80 takes an 80387 at the processor's speed: FRU 72X6673 (16 MHz), 90X7393 (20 MHz) or 15F7661 (25 MHz). IBM warns that the wrong coprocessor can cause intermittent errors. The bevelled corner faces the bottom and rear of the system on the -041 and -071, the bottom and front on the 20 MHz models, and the top and rear on the 25 MHz models.

Diskette drive

The drives take their power through the interface and have no separate power connector. The -Axx machines use a pin-connector drive and the earlier models a card-edge drive. Fred Spencer ran pin-style drives on a 20 MHz board, but Ardent Tool reports electrical differences that could damage the board. IBM's 1990 parts list gives FRU 72X8523 for the half-height 1.44 MB drive and 33F8211 for the one-third-height drive.

• The drives are direct drive and have no belt. Mitsubishi's MF355C specification, for example, describes a DC brushless motor driving the spindle at 300 rpm.
• Peter Wendt's causes of a 162 with the drive dead at POST: POST moves the heads out from track 0 and back within a fixed time, and a sticking head carriage (hardened grease or dirt on the guides), a dirty track-0 sensor or a head damper pad that has come unstuck makes it miss. He found the ALPS drives more troublesome than the Mitsubishi, with the damper pad the usual fault on older ALPS drives, and dirt round the head actuator spindle the usual fault on the Mitsubishi 355. He recommends Tamiya ball-gear grease for the head guides and servo spindle.
• 6xx errors come from failed surface-mount electrolytics on the drive's logic board or from dirt on the system board's diskette controller; see IBM PS/2 Model 80 Capacitor Replacement Guide.

Fixed disks

The 44 MB drive is ST-506, the 70, 115 and 314 MB drives ESDI, and the later drives SCSI, each on its own adapter card with 4-pin power leads. The drives park their heads at power-off, and IBM warns that careless shipping or handling can destroy the data and formatting, so back the drive up before moving the machine. IBM's removal notes say the drive in the rear bay must have its terminator fitted (on a two-drive rear bracket, the drive nearest the system board), and the drive in the front bay must have its terminator removed.

• 1780 on an 8580-041: IBM retain tip H064300 says to check that the fixed-disk cables are installed correctly.
• A second 314 MB drive in a -311 that will not come ready: ECA 040, a fault in the drive logic board.
• ESDI codes 010450XX, 010451XX and 010490XX-010499XX: run Advanced Diagnostics, then change the drive and the system board; 010454XX is a sector-buffer test error, 010455XX and 010456XX controller errors, 010462XX a controller seek error and 010464XX a drive read error.
• A drive that will not spin up after long storage: Peter Wendt's method for stiction is to unplug the system unit, shake it up and down a few times, turn it sharply clockwise a few times and switch on. Do not drop the front of the unit on the desk. Copy the data off as soon as the drive runs.

Engineering changes

The ECA list is on the Model 80 page. Two are worth checking on any machine:

• ECA 031 and ECA 048: early 20 MHz boards (planar FRU 90X7390 below EC C00835, and FRU 33F8415) have trouble with bus-master adapters, usually seen as a 110 parity error. ECA 048 names the IBM Wizard, Portmaster and XGA, BICC Isolan, ComTech Channel/2, Metacomp Psconnect, Northern Telecom LanStar/MC, Proteon P1840, Racore 4x16 and Yarc Micro785+.
• ECA 051: on an -A16, -A21 or -A31 with 8 MB on the system board and intermittent OS/2 Trap 0002 or NMI errors, look at the modules at U24 and U34, near J8 and J9. If either is marked FCT841 the board qualifies for replacement; other markings such as F841, 841D, 72F841 and 72F841D are good. Read the marking on the module itself, not the print on the board beside it.

Mistakes to avoid

• Pulling the battery lead off the system board while taking the front bezel off. The configuration goes with it.
• Fitting a second adapter that drives the VGA signals. IBM warns that some non-IBM graphics adapters drive the VGA signals instead of receiving them, and two such adapters damage each other.
• Swapping base frames between models. Retain tip H021673: FRU 64F0157 (the -041 to -321) has a metal back plane needed for EMC that must not be removed; FRU 64F0158 (the 25 MHz models) has none, because that board has components on its solder side.
• Fitting a pin-style diskette drive to a 16 MHz or 20 MHz board.

Tools

• A volt-ohm meter (IBM names one "similar to the Triplett Model 310") and the Tri-Connector wrap plug 72X8546 for the port diagnostics.
• A coin or large flat blade for the cover screws.
• A security Torx bit for the supply case screws.
• A compressor with a fine nozzle, a soft brush, a vacuum cleaner, cotton buds and isopropyl alcohol.
• The Model 70/80 Reference Diskette and the option diskettes for every adapter.
• A CR-P2 type 6 V lithium pack.
• An anti-static wrist strap.

See also Recommended Tools.

Related pages

• IBM PS/2 Model 80
• IBM PS/2 Model 80 Troubleshooting Guide
• IBM PS/2 Model 80 Capacitor Replacement Guide
• IBM PS/2 Model 60 Maintenance Guide (same case)
• IBM PS/2 Model 70 Maintenance Guide
• Battery Refurbishment
• Floppy Drive Repair
• Hard Drive Maintenance and Repair