Editing IBM Model F (83-key)

{{Infobox computer peripheral
| name          = IBM Model F (83-key XT layout)
| image         = [[File:IBM Model F XT keyboard.jpg|260px]]
| caption       = IBM Model F (83-key, XT layout) keyboard, German variant pictured
| manufacturer  = IBM
| type          = Capacitive buckling-spring mechanical keyboard
| release_date  = August 1981 (with the IBM PC)
| discontinued  = 1985 (replaced by Model M)
| interface     = 5-pin DIN (XT protocol — not AT-compatible without converter)
| compatible    = [[IBM PC (5150)]], [[IBM PC XT (5160)]], any XT-protocol clone
| dimensions    = 19" × 9" × 1.5" (485 × 228 × 38 mm)
| weight        = 7 lb 4 oz (3.3 kg)
| model         = 4584656, 4176191, 1801449 and others
}}

The '''IBM Model F (83-key)''' is the original IBM Personal Computer keyboard, shipped from 1981 to 1985 with the [[IBM PC (5150)]] and [[IBM PC XT (5160)]]. The 83-key XT layout has function keys F1-F10 in two columns on the left side, no separate cursor cluster (the numeric keypad doubles as cursor keys), and a steel-and-zinc internal construction.

The Model F uses a '''capacitive buckling-spring''' switch design — each key has its own barrel containing a spring that "buckles" sideways when pressed, snapping a flipper against the PCB through a foam-and-foil pad. The same buckling-spring mechanism appears in the later [[IBM Model M]] keyboard, but the Model M uses a membrane in place of the Model F's capacitive sense PCB.

== Hardware ==

* '''Switch:''' capacitive buckling-spring.
* '''Steel back plate and zinc-cast top frame.'''
* '''83 keys''' arranged in the XT layout: F1-F10 left column-pair, alphanumerics centre, numeric/cursor pad on the right.
* '''Internal MCU:''' Intel 8048-family, generating XT-protocol scan codes.
* '''Coiled DIN-5 cable''' to the host.

== Foam Pad Repair ==

The foam-and-foil pads inside each barrel degrade with age — the foam crumbles and the foil oxidises, producing dead or stuck keys. A full restoration replaces all 83 pads with modern equivalents (Modern Model F's polypads or laser-cut 3M foil sheets are common choices) and removes any residue from the sense PCB with isopropyl alcohol.

The disassembly sequence is:
# Remove the case screws on the underside.
# Lift the top shell off; the barrel plate stays attached to the steel back plate.
# Unbend the C-clips around the barrel-plate perimeter.
# Lift the barrel plate clear of the PCB.
# Carefully turn the assembly over; the springs and flippers sit loose inside their barrels.
# Replace the foam-and-foil pads, re-bend the C-clips, and reassemble.

The C-clips fatigue with repeated bending — use a soldering iron to spot-weld replacement clips if any break during reassembly.

== Compatibility ==

The 83-key Model F speaks the '''XT keyboard protocol''' — a simple unidirectional serial stream. It will '''not''' work with an AT, PS/2, or USB host directly. A small adapter (e.g. Soarer's Converter or a Pro Micro running tmk_keyboard) translates XT to PS/2 or USB.

The 84-key AT Model F (P/N 6450200, shipped with the 5170 AT) uses the bidirectional AT protocol and is not interchangeable with the 83-key XT version, although the physical case design is similar.

== Common Faults ==

* '''Dead or stuck keys''' — foam-and-foil pad degradation. Replace the pads.
* '''Whole-keyboard 301 error''' — broken conductor in the curly DIN cable at the strain relief. Replace the cable.
* '''Spurious key repeats''' — corroded sense pad PCB. Clean with isopropyl alcohol.

== References ==

* [https://en.wikipedia.org/wiki/Model_F_keyboard Model F keyboard — Wikipedia].
* [https://deskthority.net/wiki/IBM_Model_F IBM Model F — Deskthority wiki].
* [https://www.clickykeyboards.com/product/ibm-model-f-keyboard-ibm-industrial-83-key-xt/ ClickyKeyboards — IBM Model F XT 83-key listing] (dimensions and weight).

== Related Pages ==

* [[IBM PC (5150)]]
* [[IBM PC XT (5160)]]
* [[IBM Model M]] — the membrane-based successor

[[Category:IBM]]