Editing IBM PS/2 Model 80 (section)

== What Actually Fails ==

The Model 80 planar '''does not carry surface-mount aluminium electrolytic capacitors'''. Photographs of the Type 1 and Type 2 planars show through-hole dipped tantalum beads and surface-mount ceramics for rail decoupling; there are no electrolytic cans on the board to leak. The "PS/2 plague" that damages some PS/2 assemblies is not this board's failure mode.<ref name="at8580t1" /><ref name="at8580t2" />

What does fail, in rough order of how often you will meet it:

* '''Dust on the planar under the power-supply fan.''' The supply's fan draws household dust directly onto a sensitive area of the board. Conductive dust between IC pins produces lost configuration, a wildly wrong clock and disk read/write errors — faults that look like a dead battery or a dead drive. On a Model 80 board the ICs in that area are the 8042 keyboard controller, the MC146818A, the diskette controller, the NS16550 UART, the RTC crystal and sometimes an 8259A.<ref name="atcommon80" />
* '''The power switch.''' Roughly half of failed Model 80 supplies have failed on a broken power switch — the red ones more often than the white. The same switch was used in IBM 327x and 525x terminals and is known for it; it was available as a spare.<ref name="atpwr80">[https://www.ardent-tool.com/60_65_80/Power.html 60, 65 SX, and 80 — Power Supply], Ardent Tool of Capitalism. Secondary source reproducing IBM's 15-pin planar power-connector pinout and service test-voltage table for the 8560/8565/8580, the observed supply variants with their FRU numbers and output ratings, the removal procedure, Peter Wendt's note on the high failure rate of the power switch, and Fred Spencer's fixed-disk power-consumption figures.</ref>
* '''The diskette drive''', whose logic board uses surface-mount electrolytics that go open-circuit or high-ESR.<ref name="atfdd">[https://www.ardent-tool.com/floppy/8580.html 8580 Diskette Drives], Ardent Tool of Capitalism, content by Fred Spencer and Al Savage. Source for the PS/2 diskette-drive part numbers (P/N 90X6766, FRU 72X8523 card-edge; FRU 64F0162 pin-interface), for Al Savage's teardown of a Mitsubishi MF355W-99M3 identifying five failed surface-mount electrolytics — two 22 µF/16 V, one 1 µF/50 V and two 0.22 µF/50 V — for the diskette-controller dirt problem under the power-supply fan, and for Peter Wendt's list of mechanical causes of a 162 at POST.</ref>
* '''The battery pack''', which is a consumable.<ref name="atbatt" />

See [[IBM PS/2 Model 80 Capacitor Replacement Guide]].