IBM PS/2 Model 60 Capacitor Replacement Guide

This guide documents capacitor diagnosis and replacement for the IBM PS/2 Model 60 (machine type 8560, submodels -041 and -071), covering the planar, the 207 W / 225 W PSU, the IBM Fixed Disk Adapter/A (ST-506 controller) and ESDI Fixed Disk Adapter/A (ESDI controller), the floppy and hard drive logic boards. The Model 60 PSU is electrically different from the Model 50 94 W PSU but shares many internal cap values with the Model 80 PSU.

Safety Warning

The 207 W (8560-041) and 225 W (8560-071) PSUs contain mains-rectified bulk capacitors that hold a lethal charge after power-off. Before any PSU work:

Power off and unplug the mains lead.
Wait at least 30 seconds.
Discharge the bulk capacitor through a 1 kΩ / 5 W resistor.
Verify with a multimeter.

The tower's PSU is larger than the Model 50's and the bulk cap is correspondingly larger; discharge time may be longer in practice.

Planar Capacitors

The Model 60 planar carries through-hole 10 µF / 16 V tantalum capacitors for IC supply rail bypassing, the same as the Model 50. The Model 60 is less affected than the Model 70 / 80 by surface-mount aluminium electrolyte leakage, but planar tantalum shorts and through-hole electrolytic ageing occur in field service.

Failure Modes

Tantalums on the Model 60 are commonly marked "106 16V" (10 µF, 16 V working voltage), polarised. Two failure modes:

Short circuit — pulls +5 V or +12 V down. PSU folds back (Power Good not asserted in 150 ms); system shows "click then nothing" or repeated click-retry.
Open circuit — no immediate symptom; decoupling degraded; system noise-sensitive.

Diagnostic Procedure

Discharge the PSU bulk capacitor.
Remove the planar from the chassis floor (drive cage and MCA riser must be lifted out first).
Set multimeter to diode test or 200 Ω resistance.
Probe each tantalum in-circuit: black probe to ground, red probe to the rail side. Good cap reads as open / high resistance after a brief charge pulse; a failed (shorted) cap reads close to 0 Ω.
Where a short is found, remove the cap to confirm out-of-circuit; other components on the same rail can give false-short readings.
Replace with a fresh 10 µF / 16 V tantalum (preferred) or 10 µF / 25 V low-ESR ceramic (acceptable substitute).

Removal and Replacement

Mark polarity with a paint pen or photograph.
Apply fresh solder + flux to both leads from the underside.
Heat one pad, lever the cap up with tweezers. Heat the other pad and lift clear.
Clean both holes with solder wick.
Insert the new cap matching the silkscreen polarity (+ on cap to + on silkscreen).
Solder both leads from the underside. Inspect for a clean fillet.
Trim leads flush.

Use a temperature-controlled iron at no more than 350 °C; limit each desolder cycle to 5–7 seconds. The Model 60 planar pads are no more forgiving than the Model 50's.

207 W PSU Recap (8560-041)

The 207 W PSU is a single-board switching supply with the standard primary / secondary topology:

Primary side: bridge rectifier, X2 line suppression cap on the mains input, 220 µF / 200 V bulk capacitor, switching transistor, switching transformer.
Secondary side: rectifier diodes, smoothing electrolytics, output filter chokes, feedback optocoupler.

After 30+ years, secondary electrolytics commonly need replacement. Symptoms include sagging rails under load, audible whine, PSU refusing to start when warm, fan stutter.

**Model 60 207 W PSU capacitor replacement summary**
Value	Voltage	Type	Typical position	Notes
2200 µF	16 V	Low-ESR aluminium electrolytic, 105 °C	+5 V smoothing × 2	Critical for +5 V stability at high MCA load
1000 µF	35 V	Low-ESR aluminium electrolytic, 105 °C	+12 V smoothing × 1	Drive motors run from this rail
470 µF	35 V	Aluminium electrolytic, 105 °C	+12 V auxiliary × 1
220 µF	35 V	Aluminium electrolytic, 105 °C	−12 V smoothing × 1
100 µF	50 V	Aluminium electrolytic, 105 °C	Primary auxiliary × 2
100 µF	16 V	Aluminium electrolytic, 105 °C	Bypass / feedback × 2–3
47 µF	50 V	Aluminium electrolytic, 105 °C	Primary startup × 1
220 µF	200 V	Aluminium electrolytic, 105 °C	Primary bulk × 1	Lethal charge — discharge before work
0.1 µF	275 VAC	X2 class	Mains suppression × 1	Replace if RIFA-branded

225 W PSU Recap (8560-071)

The 225 W PSU (uprated for the 70 MB ESDI drive's higher startup current) shares the same topology as the 207 W PSU but with larger filtering on the +12 V rail.

**Model 60 225 W PSU capacitor replacement summary (delta from 207 W)**
Value	Voltage	Type	Position
2200 µF	16 V	Low-ESR aluminium electrolytic, 105 °C	+5 V smoothing × 2
2200 µF	25 V	Low-ESR aluminium electrolytic, 105 °C	+12 V smoothing × 1 (larger than 207 W's 1000 µF / 35 V)
470 µF	35 V	Aluminium electrolytic, 105 °C	+12 V auxiliary
220 µF	35 V	Aluminium electrolytic, 105 °C	−12 V smoothing
220 µF	200 V	Aluminium electrolytic, 105 °C	Primary bulk
100 µF	16 V	Aluminium electrolytic, 105 °C	Bypass / feedback × 2–3
100 µF	50 V	Aluminium electrolytic, 105 °C	Primary auxiliary × 2
47 µF	50 V	Aluminium electrolytic, 105 °C	Primary startup
0.1 µF	275 VAC	X2 class	Mains suppression

Recap Procedure

Discharge the bulk capacitor; verify with a multimeter.
Remove the PSU from the top of the chassis (4 screws).
Open the PSU housing. The Model 60 PSU shell is normally screwed (not ultrasonically welded).
Photograph the board before any work. Mark each electrolytic's polarity with a paint pen.
Desolder each electrolytic. Use solder wick on each lead.
Fit replacements: low-ESR, 105 °C rated, equal capacitance, equal or higher voltage rating.
Inspect the X2 mains suppression capacitor. If RIFA-branded or showing cracking, bulging or fluid leakage, replace with a modern X2 cap of equal value. RIFA X2 caps from this era are notorious for venting and producing the classic "smell of fish" odour.
Reassemble. Verify rails on the bench with a multimeter under a 1 A resistive load before refitting to the chassis.

ESDI Fixed Disk Adapter/A Capacitors

The IBM ESDI Fixed Disk Adapter/A drives the 70 MB ESDI hard drive on the 8560-071. The card carries small aluminium electrolytics that age:

10 µF / 16 V (multiple positions) — IC bypassing.
22 µF / 16 V (one or two positions) — sector buffer power.
47 µF / 16 V (one position) — on-card 5 V regulation.

If the ESDI controller reports a 10455 (controller failure) or 10463 (read/write sector error) on a known-good drive, recap the controller card capacitors before condemning the card.

Fixed Disk Adapter/A (ST-506) Capacitors

The IBM Fixed Disk Adapter/A on the 8560-041 carries similar through-hole electrolytics in similar positions (10 µF / 22 µF / 47 µF on +5 V bypassing). Recap if 1701 / 1702 errors appear on a known-good drive.

ESDI Drive Logic Board

The Maxtor / Miniscribe / Western Digital 70 MB ESDI drives in the 8560-071 carry their own drive logic board with aluminium electrolytics. Typical values:

47 µF / 16 V — near the spindle motor driver.
10 µF / 25 V — near the head-amp section.
22 µF / 16 V — sector buffer.

Symptoms of aged drive caps include the drive not spinning up reliably, CRC errors on reads, and the drive becoming unreliable when warm. Recap with 105 °C low-ESR equivalents.

ST-506 Drive Logic Board

The 44 MB ST-506 drive on the 8560-041 (an IBM-branded drive, PS/2-specific firmware) carries similar small electrolytics. The PS/2 ST-506 drive family is distinct from the Seagate ST-506 of the IBM AT — they share the chassis interface but not the firmware. Recap with 105 °C low-ESR equivalents if drive becomes unreliable.

Floppy Drive Logic Board

The PS/2 1.44 MB floppy drives (ALPS, Mitsubishi MF355C, Sony, YE-Data) carry:

47 µF / 16 V — motor driver.
10 µF / 25 V — head amplifier.

Leak symptoms include brown crust around the cap base and corroded PCB traces. Clean with IPA and replace with 105 °C low-ESR equivalents.

The Mitsubishi MF355C family also needs a 54 × 1 mm flat rubber drive belt at the same time.

MCA Memory Card Capacitors

The IBM 2-8 MB MCA Memory Adapter/A carries through-hole electrolytics that age but rarely fail. Inspect for leaked electrolyte if a memory card is fitted and the system reports 201 / 215 / 216 errors on it.

Replacement Parts Summary

**Model 60 system-wide cap replacement summary**
Value	Voltage	Type	Where
10 µF	16 V	Tantalum or low-ESR ceramic	Planar bypass, ESDI / ST-506 card bypass
22 µF	16 V	Tantalum or low-ESR aluminium	ESDI sector buffer, planar bypass
47 µF	16 V	Aluminium electrolytic, low-ESR, 105 °C	Drive logic board motor driver; ESDI card +5 V regulation
47 µF	50 V	Aluminium electrolytic, 105 °C	PSU primary startup
100 µF	16 V	Aluminium electrolytic, low-ESR, 105 °C	PSU bypass / feedback
100 µF	50 V	Aluminium electrolytic, 105 °C	PSU primary auxiliary
220 µF	35 V	Aluminium electrolytic, 105 °C	PSU −12 V smoothing
220 µF	200 V	Aluminium electrolytic, 105 °C	PSU primary bulk (lethal-charge component)
470 µF	35 V	Aluminium electrolytic, 105 °C	PSU +12 V auxiliary
1000 µF	35 V	Low-ESR aluminium electrolytic, 105 °C	207 W PSU +12 V smoothing
2200 µF	16 V	Low-ESR aluminium electrolytic, 105 °C	PSU +5 V smoothing (both 207 W and 225 W)
2200 µF	25 V	Low-ESR aluminium electrolytic, 105 °C	225 W PSU +12 V smoothing
0.1 µF	275 VAC	X2 class	PSU mains suppression

Polarity Reference

The Model 60 planar silkscreen marks the + (positive, rail) side of each electrolytic with a small "+". The cap body shows the negative side with a stripe and "−". Match these conventions.

A failed tantalum often shows no visible damage.

Failed tantalum on an IBM motherboard. The small hole on the body is often the only visual indication. (Image: minuszerodegrees.net)

Post-Recap Verification

Bench-test the planar with a known-good PSU and no peripherals.
Verify rails at the planar power connector.
Refit; boot the Reference Diskette.
Run Auto Configuration if any MCA cards changed.
Run Advanced Diagnostics (Ctrl-A) and walk through each test.
Run a memory test pass for several hours under DOS to confirm planar memory reliability.
Run a drive surface scan to confirm the ESDI / ST-506 subsystem is healthy after controller recap.

If any test fails after a recap, re-inspect the polarity of every replaced cap before suspecting another fault — reversed polarity is the most common error.

When Not to Recap

If the Model 60 boots, POSTs cleanly and runs reliably with no diagnostic errors, the caps are within tolerance.

Always recap if:

Fluid leak visible from any electrolytic.
PSU smoke, fishy odour or audible whine.
Diagnostic procedure identifies a shorted tantalum.
ESDI controller reports 10455 / 10463 on a known-good drive.
Drive becomes unreliable when warm.
Rails sag below tolerance under load.

Related Pages

IBM PS/2 Model 60
IBM PS/2 Model 60 Maintenance Guide
IBM PS/2 Model 60 Troubleshooting Guide
IBM PS/2 Model 50 Capacitor Replacement Guide — desktop sibling, 94 W PSU
IBM PS/2 Model 80 Capacitor Replacement Guide — same tower chassis, related PSU topology
Capacitor Failure Symptoms

References

Commonly Failing Electronic Components, minuszerodegrees.net. Reference for tantalum and aluminium electrolytic failure modes.
IBM PS/2 Model 60 — Ardent Tool Quick Reference. FRU breakdown and PSU rating.
IBM, IBM Personal System/2 Hardware Maintenance Manual (S52G-9971-02, October 1994).