IBM 5151
| IBM Monochrome Display | |
|---|---|
 |
|
| IBM 5151 Monochrome Display | |
| Manufacturer | IBM |
| Type | TTL monochrome CRT monitor |
| Release date | 1981 (with the original IBM PC) |
| Interface | TTL digital, 9-pin D-shell (driven by the IBM Monochrome Display Adapter) |
| Compatible | IBM PC (5150), IBM PC XT (5160), IBM PC AT (5170), MDA-compatible systems |
| Dimensions | 280 mm H × 380 mm L × 350 mm D |
| Weight | 7.9 kg (17.3 lb) |
| Model | 5151 (IBM publication 6361474) |
The IBM 5151, which IBM called the IBM Monochrome Display, is the green-phosphor TTL monitor sold with the original IBM PC (5150) when it was ordered with the IBM Monochrome Display Adapter (MDA). It displays text only, 80 characters by 25 rows. Each character sits in a 9 by 14 dot box, which gives 720 by 350 dots on screen and makes MDA text sharper than CGA text.[1]
Display characteristics
[edit | edit source]IBM's figures:[1]
| Item | IBM figure |
|---|---|
| CRT | 28.3 cm (11.5 in) diagonal, 90° deflection |
| Phosphor | P39, high persistence, green; etched surface to reduce glare |
| Text | 80 characters by 25 rows; characters in a 14 PEL high by 9 PEL wide matrix |
| Vertical | 50 Hz refresh, 350 lines vertical and 720 lines horizontal resolution |
| Horizontal drive | Positive-level TTL, 18.432 kHz |
| Video bandwidth | 16.257 MHz maximum at −3 dB |
| Heat output | 325 BTU/hr |
| Cables | Power 0.914 m (18 AWG); signal 1.22 m (22 AWG) |
IBM states that the MDA does not support a light pen when used with a P39-phosphor display such as this one.[2]
Measured at the adapter, MDA horizontal sync is an 8 µs positive-going pulse every 54.3 µs and vertical sync an 850 µs negative-going pulse every 20 ms. CGA horizontal sync runs at about 15.7 kHz, well below the 5151's 18.43 kHz, so a 5151 cannot be driven from a CGA card.[3]
Power
[edit | edit source]The 5151 has no mains plug of its own. The signal cable comes from the display adapter, and a second cable takes ac power from a switched socket on the back of the PC's power supply, so the system unit's power switch turns the display on and off.[1] IBM's technical reference rates that outlet at 0.75 A and says it is provided only for the IBM Monochrome Display.[4]
There are two models, one for 110 Vac and one for 220/240 Vac, and IBM prints a separate logic diagram for each.[1]
Input connector
[edit | edit source]A 9-pin D-shell at TTL levels: 0.0 to 0.6 V down level and +2.4 to 3.5 V up level.[2]
| Pin | Signal |
|---|---|
| 1 | Ground |
| 2 | Ground |
| 3, 4, 5 | Not used |
| 6 | + Intensity |
| 7 | + Video |
| 8 | + Horizontal sync |
| 9 | − Vertical sync |
Pins 3, 4 and 5 are missing from the 5151's plug. That is normal, because MDA does not use them.[5] The combination of the Video and Intensity lines gives three levels: off, normal and bright.[2]
Common faults
[edit | edit source]The fault notes below are from minuszerodegrees.net.[5]
- Stiff brightness and contrast knobs are normal on a 5151, and IBM may have intended it.
- A stable raster with the brightness turned up but no characters means the 5151 is getting correct horizontal and vertical sync from the MDA card. Check, in order: the contrast control; the MDA card (it may be producing sync but no video); the video wire in the cable; the connection at pin 7 of the plug; then the video path inside the monitor. IC201, an SN7406A, has been reported failed by at least two owners.
- No raster at all, even with the brightness turned up. The 5151 needs horizontal sync from a working, initialised MDA card before it will show a raster. Check that the card is there, seated and initialised; motherboard switches set to EGA instead of MDA leave it uninitialised. A faulty motherboard or card, or oxide on the connector pins, has the same effect.
- Full or partial vertical collapse. minuszerodegrees.net publishes the vertical deflection circuit and waveforms for this fault.
- A bright spot or line at switch-off is normal.
A horizontal sync signal that does not meet the MDA standard can damage a 5151, and software alone can cause one by reprogramming the 6845 on the adapter; minuszerodegrees.net links an AST technical bulletin describing such a case.[5] Avoid untested display software on a 5151.
CRT safety
[edit | edit source]The CRT keeps a dangerous anode charge after the set is switched off and unplugged. Discharge it before working inside; see CRT Discharge Procedure.
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 IBM, IBM Monochrome Display (6361474), Options and Adapters, Personal Computer Hardware Reference Library, pp. 1 to 5: description, specifications and the logic diagrams for the 110 Vac and 220/240 Vac models. Hosted here as File:IBM Options and Adapters - IBM Monochrome Display (5151).pdf and described at IBM Options and Adapters - IBM Monochrome Display.
- ↑ 2.0 2.1 2.2 IBM, IBM Monochrome Display and Printer Adapter, Options and Adapters, Personal Computer Hardware Reference Library: the 6845 CRT controller, the 4 KB display buffer, the character box, the 18 kHz monitor requirement, the note that a light pen is not supported with a P39 display, the connector pin assignments and TTL levels. Hosted here as File:IBM Options and Adapters - IBM Monochrome Display and Printer Adapter.pdf and described at IBM Options and Adapters - IBM Monochrome Display and Printer Adapter.
- ↑ IBM: MDA / CGA / EGA, minuszerodegrees.net: 9-pin assignments for MDA, CGA and EGA, sync frequencies, and sync pulse shapes measured on IBM cards.
- ↑ IBM, IBM Personal Computer Technical Reference (5150), section 3 "Power Supply". Hosted here as File:IBM PC 5150 Technical Reference.pdf and described at IBM PC 5150 Technical Reference.
- ↑ 5.0 5.1 5.2 IBM 5151: Known Problems/Issues, minuszerodegrees.net.
Related pages
[edit | edit source]- IBM Monochrome Display Adapter, the adapter that drives the 5151
- IBM 5153, the colour equivalent
- IBM PC (5150) · IBM PC XT (5160) · IBM PC AT (5170)
- IBM Options and Adapters - IBM Monochrome Display · IBM Personal Systems Reference - Monitors
- CRT Discharge Procedure · Capacitor Failure Symptoms