IBM PS/2 Model 30 Maintenance Guide

An IBM PS/2 Model 30 286 (8530-E series). The 286 machines are the ones with a voltage selector switch on the rear and a Dallas RTC module on the planar. (Image: DigitalIceAge, CC BY 4.0, via Wikimedia Commons)

This guide documents preventive maintenance on the IBM PS/2 Model 30 (machine type 8530), covering both the original Model 30 8086 (8530-002 and 8530-021) and the later Model 30 286 (8530-E01, E21, E31, E41). The Model 30 is a desktop-form-factor PS/2 with no integrated CRT, unlike the Model 25, so the system unit can be opened and worked on at the bench with far less electrical risk.

Safety Warning

The power supply rectifies the mains directly and its bulk capacitor holds that charge after the lead is pulled — roughly 170 V on a 120 V mains, roughly 325 V on a 230 V mains. Before any work inside the supply's shell:

1. Power off and unplug the mains lead.
2. Bleed the bulk capacitor through a resistor across its terminals (1 kΩ / 5 W is the usual workshop choice).
3. Confirm on a DC range that it is down to a few volts.

If your machine is a Model 30 286, check the voltage selector switch on the rear before plugging the cord in. It must be set to the 100–125 Vac or the 200–240 Vac range to match your supply. The 8086 Model 30's supply is the internal-sensing type and has no switch.

There is no CRT inside the Model 30 itself, so the anode-discharge procedure needed on the Model 25 does not apply unless you are servicing the matching PS/2 display, in which case see CRT Discharge Procedure.

Identifying Your Model

Model 30 generation identification

Marker	Model 30 8086	Model 30 286
Machine types	8530-002, 8530-021	8530-E01, E21, E31, E41
CPU	Intel 8086-2 at 8 MHz, at planar U10	Intel 80286 at 10 MHz, at planar ZM36 (PGA socket on early boards, PLCC on later)
Chipset	IBM gate arrays	VLSI VL82CPCAT-QC, at ZM2–ZM6
Video	MCGA	VGA
Riser	three 8-bit ISA slots	16-bit ISA
Extra bus power connector	absent	present (J14, 4-pin, feeds the 16-bit bus)
Real-time clock	NS MM58167AN at planar U16, battery on the riser card	Dallas DS1287 module at ZM35, cell sealed inside
Diskette drive as shipped	720 KB	1.44 MB
Power supply	70 W, internal sensing, no voltage switch	90 W, dual voltage, switch on the rear

Sources for this table: the planar designator maps, IBM's announcement letters, and IBM's Technical Reference.

The machine type and submodel are printed on the rear panel label, for example "Type 8530-E21".

Planar Layout

The 8086 planar exists as the original "P-PLANAR" P/N 61X8823 and two later Greenock builds, P/N 33F4888 and FRU P/N 33F8474 (P/N 33F4871). The layouts look nothing like each other, but the reference designators are largely consistent across all of them — and across the 8086-based Model 25 planars too, which makes this map useful on either machine.

Model 30 8086 planar — principal designators

Designator	Device
J1 / J2	Mouse / keyboard connectors (Mini-DIN-6, not interchangeable)
J3	Parallel port (DB-25)
J4	Video connector (HD-15)
J5	Serial port (DB-25)
J6	Riser slot
J7, J9	Power connectors
J10	2-pin keylock header
J11	44-pin fixed-disk connector
J12	40-pin diskette connector
J13	Dual 30-pin SIMM socket
F1 / F2	Mouse and keyboard fuses (combined into F1 on the later alternative Greenock board)
U5	Inmos IMSG171S RAMDAC
U8	Intel P8253-5 timer
U10	Intel 8086-2 CPU, 8 MHz
U13	8087 coprocessor socket
U16	NS MM58167AN real-time clock
U17, U20	ROM BIOS (even / odd)
U18	NEC µPD765AC diskette controller
U19	8237A DMA controller
U27	NS8250AV UART
SP1	Piezo speaker
Y1 / Y2 / Y3	14.31818 MHz / 25.175 MHz / 48.000 MHz oscillators
Y4	32.768 kHz crystal (real-time clock)

On the 286 planar the numbering changes to a ZM prefix: ZM2 VL82C100 peripheral controller, ZM3 VL82C102A memory controller, ZM4 VL82C103A address buffer, ZM5 VL82C104 data buffer, ZM6 VL82C101B system controller, ZM9 VL16C451 parallel/UART, ZM19 µPD765AC-2 diskette controller, ZM33 8042/8742 keyboard controller, ZM35 Dallas DS1287 RTC/CMOS, ZM36 the 286 CPU. Power arrives at J7 and J14, and J13 is the password-override jumper.

Opening the System Unit

Tools: a Philips screwdriver, an anti-static strap and a plastic spudger.

1. Turn off the system unit and every external option.
2. Unplug the system unit's power cord from the outlet, then the cords of any external options.
3. Remove all cables from the rear of the system unit.
4. If the machine has a cover lock, unlock it and remove the key.
5. Loosen the two cover screws and lift the cover off.

A Model 30 286 with the cover off. The drive cage sits over the planar, the power supply alongside it, and the riser card at the rear. Drives and cards are held by plastic captive push-pin fittings, not screws. (Image: DigitalIceAge, CC BY 4.0, via Wikimedia Commons)

Inside, the drive cage sits over the planar and the supply is alongside it; the riser card mounts at the rear. Cards on the riser and the drives are held by IBM's plastic captive push-pin fittings. Lever these with a plastic spudger, never a metal screwdriver — the pins are brittle with age and snap, and a broken captive pin means the drive cage no longer locates properly.

Regular Cleaning

• Soft brush and low-pressure compressed air for the planar, riser, drives and supply vents. Hold any fan blades still by hand while blowing, so the fan is not spun beyond its rated speed.
• Clean the Mini-DIN-6 keyboard and pointing-device connectors with a deoxidising contact cleaner on a foam swab, sparingly.
• Clean the DB-25 parallel and serial connectors.
• Inspect the planar for leaked electrolyte, and the diskette drive boards more carefully still — that is where PS/2 capacitor damage actually shows up. See IBM PS/2 Model 30 Capacitor Replacement Guide.

PSU Voltage Checks

Power reaches the planar through two 6-pin connectors, P3 and P4. P3 is the one nearer the rear of the system.

Model 30 power supply connector pin assignments

Pin	P3	P4
1	Power Good	Ground
2	Ground	Ground
3	+12 V dc	−5 V dc
4	−12 V dc	+5 V dc
5	Ground	+5 V dc
6	Ground	+5 V dc

Measure with the system powered on and running. IBM's service limits are given between specific pins, so put the meter's negative lead where the table says:

Model 30 and Model 30 286 — service measurement limits

Rail	Negative lead	Positive lead	Minimum	Maximum
+5 V	P3-5	P4-4	+4.8 V	+5.2 V
−5 V	P4-3	P3-6	+4.6 V	+5.5 V
+12 V	P4-1	P3-3	+11.5 V	+12.6 V
−12 V	P3-4	P4-2	+10.8 V	+13.2 V

The negative rails are measured with the leads reversed, which is why they read as positive numbers.

The supply shuts itself down if a rail falls below its under-voltage sense level: +4.5 V on the +5 V rail, −4.3 V on −5 V, +10.8 V on +12 V and −10.2 V on −12 V. A rail sitting just above its trip point will run on the bench and then drop the machine as soon as it is loaded.

Power Good should read +3.5 V to +5 V at P3-1 when the system is operating correctly. If it does not, strip out all adapters, cables and extra memory and try again; if Power Good comes up, one of those devices was shorting a rail, and you find it by reinstalling them one at a time. IBM specifies the line as TTL-compatible, active at 2.4 to 5.25 V dc, inactive at 0.0 to 0.4 V dc, with a turn-on delay of not less than 100 ms and not more than 500 ms.

The Model 30 286's supply adds the 4-pin bus power connector; other than that connector the two supplies are interchangeable in the chassis. Do not fit a Model 25 supply: the Model 25 8086 does not use the same power connector as the Model 30 8086.

Real-Time Clock and Battery

Both generations have a hardware real-time clock. IBM lists "Real-time clock with battery" among the 8086 Model 30's integrated system-board functions, with the clock at I/O addresses hex 00B0–00BF (command/status) and hex 00E0–00EF (counter/RAM).

Model 30 8086

The clock is a National Semiconductor MM58167AN at planar position U16, timed by the Y4 32.768 kHz crystal.

The cell that backs it is not on the planar. It is a 3 V lithium Panasonic BR-2/3A soldered to the riser card at B1 — riser P/N 61X8864 or 61X8910, which also carries the three 8-bit ISA slots and, apart from the battery, nothing else of consequence. If the clock on an 8086 Model 30 will not hold time, pull the riser, not the planar. This catches people out: the riser is the last place most restorers look for a battery.

IBM's own service notice on the subject is worth knowing about, because the early manual got it wrong. Retain tip H067282 records that early releases of the 8530 Hardware Maintenance Service manual, on system board map page 0100-4, label the bus adapter card's pins incorrectly: the pins printed as "0" and "39" are actually pins 1 and 40, and the voltage should be measured at pins 38 and 39 — the second and third pins in from the right-hand edge. Replace the bus adapter card if the voltage between the correct pins is below 2.5 V.

Model 30 286

The clock is a Dallas DS1287 RTC/CMOS module at ZM35, a 24-pin DIP with the lithium cell sealed inside it. When the cell runs down, POST reports:

• 161 — battery. IBM's FRU order for this code is battery, then complex, then system board, then bus adapter.
• 162 — configuration changed; check that all devices are powered on and that the configuration has not been altered, then run Automatic Configuration. If that does not clear it, suspect the battery.
• 163 — date and time error; set the date and time.
• 167 — clock not running correctly.
• 168 — real-time clock error; run Advanced Diagnostics. This is not always a hardware failure.

Replacement is by desoldering the 24-pin DS1287 and fitting a fresh DS12887+ or equivalent; some restorers instead cut into the original module's case to reach the cell and fit an external holder. IBM's own caution on the 161 code is worth repeating: the lithium cell presents a fire, explosion and burn risk — do not heat, crush, short or recharge it. See Battery Refurbishment and Battery Explosion, Capacitor or Corrosion Damage.

After either job, boot the Reference or Starter Diskette and run Set Configuration to re-enter memory size, drive type and the date and time.

Power-on password

If the power-on password on a Model 30 286 is forgotten, move the J13 jumper on the planar to its other position: if it covers the first and second pins, move it to the second and third, and vice versa. Leave it where you moved it until the next time it needs resetting.

Connector Care

• Keyboard and pointing device (Mini-DIN-6): these are two physically identical sockets with different functions — J1 is the mouse, J2 the keyboard. They are not interchangeable. The plastic key aligns the plug; do not force it.
• Keyboard and mouse fuses: F1 and F2 on the planar protect the +5 V feed to the two ports, combined into a single F1 on the later alternative Greenock board. A 305 at POST is a keyboard voltage error, and IBM's first FRU for it is the keyboard port fuse.
• Parallel port (DB-25) and serial port (DB-25 on the 8086 planar) are conventional.

Single-Cable Drive Interface

The PS/2 drive interface carries power and data in one ribbon cable from the planar to the drive; there are no Molex connectors anywhere in the machine. IBM's published pin assignments show exactly where the power sits:

• Diskette (J12, 40-pin): pin 38 is +5 V dc and pin 40 is +12 V dc; odd-numbered pins 1 to 35 are signal ground.
• Fixed disk (J11, 44-pin): pins 30 and 32 are +5 V dc, pins 40, 42 and 44 are +12 V dc.

Care points:

• Align the cable's stripe to pin 1 at both ends.
• Because the supply rails ride on the same connector as the data lines, a mis-inserted or offset cable puts +12 V onto signal pins. Check the alignment twice before powering up.
• The drives have no dust shutter, so dust reaches the heads. Clean periodically.

Diskette Drive Maintenance

• The 8086 machines shipped with 720 KB drives and the 286 machines with 1.44 MB. You can tell which you have from the blue eject button: a high-density drive has "1.44MB" moulded into it.
• Use DSDD media in a 720 KB drive. A 662 at POST means the wrong drive type is installed and a 663 means the wrong media type is in the drive; 604 means an unsupported drive or cable, the drive having to be a media-sense type.
• IBM never shipped the 8086 Model 30 with a high-density drive, but the machine does have undocumented 1.44 MB support. Sony-manufactured drives are the ones likely to work; other makes are recognised only as low-density, or not at all. Which planar you have also matters — the later boards are more tolerant.
• These drives have no belt. The Mitsubishi MF355C family rotates the disk with a DC brushless direct-drive motor coupled straight to the spindle at 300 rpm. A drive that will not spin or spins slowly needs its board and motor examined, not a belt.
• The real wear item is the surface-mount electrolytics on the drive logic board, which leak and corrode the board underneath. See IBM PS/2 Model 30 Capacitor Replacement Guide and Floppy Drive Repair.

Fixed Disk Maintenance

The Model 30's fixed-disk interface is not ST-506, not ESDI and not IDE. IBM describes J11 as a dedicated I/O channel: it carries the ordinary I/O channel signals needed for fixed-disk operation — I/O read and write, reset, the data lines, I/O CH RDY, IRQ5 and the DMA request and acknowledge lines — plus a −DISK CS card-select decoded at hex 032x, a −DISK Installed line and address lines A0 to A2 to select a register inside the controller. The controller is on the drive, not on the planar: IBM's own announcement describes the 8530-021 as shipping with "one 20MB fixed disk with integrated controller".

In practice:

• Only the original IBM drive assemblies are recognised, and the setup diskette offers no other drive types.
• Those drives are failure-prone. If one will not spin up, suspect head stiction; rotating the drive body by hand with the power off sometimes frees it, but treat that as a way to get the data off, not as a repair.
• Practical replacements are an XT-IDE card on the ISA bus, an SD-based emulator, or an MFM emulator — all of which sidestep the planar interface entirely.
• The drive sits in a metal caddy held by the same plastic captive push-pin mechanism as everything else.

IBM issued a service notice about drive and board combinations on these machines. Retain tip H007157 records that successful fixed-disk operation on the 8530-001 and -021 depends on matching the system board, the drive and the version of Advanced Diagnostics used to format it — and that formatting with the wrong version of the diagnostics causes fixed-disk errors:

IBM retain tip H007157 — required FRU combinations

Machine type	System board	Fixed disk	Advanced Diagnostics
8530-021 below serial 2500000	P/N 61X8907	P/N 61X8929	8530, any version
8530-021 above serial 2500000	P/N 33F8474	P/N 6128285	8530, version 1.05
8530-001, all	P/N 33F8474	P/N 6128285 or 6128279	8530, version 1.05
8530-E21 only	P/N 27F4069	P/N 6128285	8530-286, version 1.02
8530-E31 and E01	P/N 34F0046	P/N 6128285 or 6128279	8530-286, version 1.02

Fixed disks P/N 6128285 and 6128279 must not be installed in any 8530-021 below serial number 2500000.

Known IBM Service Notices

Three more IBM notices are worth checking before chasing a fault on an 8530.

• H043664 — cursor keys and 501 POST errors. On a limited number of 8530-001 and -021 machines, the cursor keys produce unexpected characters on the display, and a 501 appears when two or more option cards are fitted. Inspect the modules at planar positions U9 (next to the coprocessor socket) and U15 (next to the speaker). U9 P/N 72X8203 and U15 P/N 61X8965 are suspect if they are marked "IBM" but do not carry the word "Japan"; good parts have it. IBM's fix was to replace the system board with FRU P/N 64F3453. Machines with serial numbers above 55-00HV000 already have the new board.
• H094152 — 8515 and 8516 displays. The 8086 Model 30 (models 001, 002 and 021) does not support PS/2 8515 or 8516 displays; attaching one gives compressed, distorted video. It does support the 8503, 8504, 8507, 8512, 8513 and 8514. The 286 machines (E01, E21, E31, E41) support the 8503, 8504, 8512, 8513, 8514, 8515 and 8516.
• H036143 — 8602 with a 4717 printer. On a Model 30 286 shipped after 1 August 1989, attaching a 4717 directly gives an 8602 POST error and the printer does not work, because a planar change grounded pin 2 of the pointing-device port. IBM's fix was an interposer cable, P/N 31F6759.

Things That Are Not Faults

• An 8086 Model 30 will not drive an 8515 or 8516 display properly. That is a documented limitation, not a fault.
• A 162 after you have added or removed a device is the machine noticing the change. Run Set Configuration before suspecting the battery.
• Soft-booting the Reference Diskette with Ctrl-Alt-Del can throw false errors and a false indication that a power-on password is already set. Cold boot with the diskette in the drive.
• A 663 means the diskette in the drive is the wrong media type for that drive. It is information, not a failure.

Capacitor Health

Tantalum beads on the planar can fail short and stop the supply from coming up; aluminium electrolytics on the diskette drive boards leak and corrode. Full procedures, including what is and is not documented about this machine's capacitors, are in IBM PS/2 Model 30 Capacitor Replacement Guide.

Recommended Tools

• Philips screwdriver and an anti-static strap.
• Plastic spudger for the captive push-pin fittings.
• Digital multimeter.
• IPA and foam swabs for connector cleaning.
• Fine-tipped soldering iron and solder wick for RTC and capacitor work.
• A replacement RTC module for a Model 30 286, or a fresh BR-2/3A-format 3 V lithium cell for an 8086 riser.
• A written copy of the model-specific Reference or Starter Diskette.

See also Recommended Tools.

Related Pages

• IBM PS/2 Model 30
• IBM PS/2 Model 30 Troubleshooting Guide
• IBM PS/2 Model 30 Capacitor Replacement Guide
• IBM PS/2 Model 25 Maintenance Guide — the all-in-one sister machine
• Hard Drive Maintenance and Repair
• Floppy Drive Repair