IBM 5151
| IBM 5151 Monochrome Display | |
|---|---|
 |
|
| The IBM 5151 12-inch green-phosphor monitor, as supplied with the original IBM PC | |
| Manufacturer | IBM |
| Type | TTL monochrome CRT monitor |
| Release date | August 1981 |
| Discontinued | ~1987 |
| Price | US$345 (1981) |
| Interface | TTL digital, 9-pin D-shell (paired with the IBM Monochrome Display Adapter) |
| Compatible | IBM PC (5150), IBM PC XT (5160), any MDA / Hercules-compatible system |
| Dimensions | 12" CRT (11.5" viewable diagonal) |
| Weight | ~9 kg (20 lb) |
| Model | 5151 |
The IBM 5151 (officially the IBM Personal Computer Display) is the 12-inch green-phosphor TTL monitor IBM shipped with the original IBM PC (5150) when it was paired with the IBM Monochrome Display Adapter. The 5151 displays 80×25 text only — it has no graphics capability — but produces an unusually crisp 720×350-pixel character image because the MDA generates a 9×14 dot character cell instead of the 8×8 cell used by CGA.
Display Characteristics
- Phosphor: P39 (long-persistence green). Reduces flicker but smears on moving content.
- Active resolution: 720 × 350 pixels, addressed as 80 × 25 characters of 9 × 14 dots.
- Horizontal scan: 18.432 kHz.
- Vertical scan: 50 Hz.
- Brightness levels: three (off / normal / bright), encoded over the TTL video + intensity pair.
- Anti-glare: etched front glass.
The 5151 will not work with CGA, because CGA runs at 15.75 kHz horizontal — well below what the 5151's flyback can lock to.
Input Connector
A 9-pin D-shell, with TTL-level signals:
| Pin | Signal |
|---|---|
| 1, 2 | Ground |
| 3-6 | (unused, reserved) |
| 7 | Video (TTL) |
| 8 | Horizontal sync |
| 9 | Vertical sync |
The 5151 derives its three brightness levels from the combination of the Video and Intensity lines on the MDA.
Common Faults
- Yoke ringing / squeal — the flyback transformer or the deflection yoke develops a high-pitched whine after decades of use. Reflow the flyback joints.
- Dim or shrunken raster — replace the analog board electrolytics, particularly on the high-voltage rail.
- Flickering brightness — the Video / Intensity TTL inputs are oxidised at the DB-9; clean with DeoxIT.
- No display, audible flyback — open filament on the CRT (rare) or failed video amplifier transistor.
CRT Safety
The 5151's CRT retains a lethal anode charge. Discharge before opening — see CRT Discharge Procedure.
Related Pages
- IBM PC (5150) — the system the 5151 was originally sold with
- IBM Monochrome Display Adapter — the adapter card that drives the 5151
- IBM 5153 — the CGA-compatible colour equivalent
- CRT Discharge Procedure