IBM 5151: Difference between revisions
Rebuild from IBM's own Options and Adapters specification (now hosted) plus minuszerodegrees: real CRT size, P39, 50 Hz/18.432 kHz, 14x9 matrix, powered from the system unit not the wall; correct 9-pin pinout incl. pin 6; real fault list incl. IC201 and the improper-sync damage warning; ref-cited |
Rebuilt from IBM's own Options and Adapters specification (now hosted here) and minuszerodegrees: corrected CRT size to 28.3 cm/11.5 in, added P39/50 Hz/18.432 kHz/14x9 matrix/720x350 from IBM, corrected 'mains powered' to powered from the system unit's switched outlet, completed the 9-pin pinout (pin 6 Intensity), replaced the generic fault list with the documented ones incl. IC201 and the improper-sync damage warning; <ref>-cited throughout |
||
| Line 1: | Line 1: | ||
{Infobox computer peripheral | {{Infobox computer peripheral | ||
| name = IBM Monochrome Display | | name = IBM Monochrome Display | ||
| image = [[File:IBM 5151 5153 5154 monitors.jpg|260px]] | | image = [[File:IBM 5151 5153 5154 monitors.jpg|260px]] | ||
| Line 7: | Line 7: | ||
| release_date = 1981 (with the original IBM PC) | | release_date = 1981 (with the original IBM PC) | ||
| interface = TTL digital, 9-pin D-shell (driven by the [[IBM Monochrome Display Adapter]]) | | 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 = [[IBM PC (5150)]], [[IBM PC XT (5160)]], [[IBM PC AT (5170)]], MDA-compatible systems | ||
| dimensions = 280 mm H × 380 mm L × 350 mm D | | dimensions = 280 mm H × 380 mm L × 350 mm D | ||
| weight = 7.9 kg (17.3 lb) | | weight = 7.9 kg (17.3 lb) | ||
| model = 5151 | | model = 5151 | ||
} | }} | ||
The '''IBM 5151''', which IBM called simply 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 80 × 25 text only — it has no graphics capability — but the MDA's large 9 × 14 character box gives an image of 720 by 350 addressable dots, which is why MDA text is visibly sharper than [[IBM Color Graphics Adapter|CGA]] text. | The '''IBM 5151''', which IBM called simply 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 80 × 25 text only — it has no graphics capability — but the MDA's large 9 × 14 character box gives an image of 720 by 350 addressable dots, which is why MDA text is visibly sharper than [[IBM Color Graphics Adapter|CGA]] text. | ||
| Line 26: | Line 26: | ||
* '''Horizontal drive:''' positive-level, TTL-compatible, at '''18.432 kHz'''. | * '''Horizontal drive:''' positive-level, TTL-compatible, at '''18.432 kHz'''. | ||
* '''Video bandwidth:''' 16.257 MHz maximum at −3 dB. | * '''Video bandwidth:''' 16.257 MHz maximum at −3 dB. | ||
* '''Heat output:''' 325 BTU/hr. | * '''Heat output:''' 325 BTU/hr. Power cable 0.914 m, signal cable 1.22 m. | ||
Measured at the adapter, | Measured at the adapter, MDA horizontal sync is an 8 µs positive-going pulse every 54.3 µs and vertical sync is an 850 µs '''negative'''-going pulse every 20 ms.<ref name="mzpins">[https://www.minuszerodegrees.net/mda_cga_ega/mda_cga_ega.htm IBM: MDA / CGA / EGA], minuszerodegrees.net. Source for the side-by-side 9-pin assignments and for the measured sync pulse shapes: MDA, an 8 us positive-going horizontal pulse every 54.3 us and an 850 us '''negative'''-going vertical pulse every 20 ms; CGA, a 4 us positive-going horizontal pulse every 63.7 us and a 190 us positive-going vertical pulse every 16.7 ms.</ref> | ||
The 5151 will '''not''' work with a [[IBM Color Graphics Adapter|CGA]] card: CGA | The 5151 will '''not''' work with a [[IBM Color Graphics Adapter|CGA]] card: CGA scans horizontally at 15.75 kHz, well outside the 5151's fixed 18.432 kHz.<ref name="mzpins" /> | ||
== Power == | == Power == | ||
The 5151 has '''no mains cord of its own'''. It takes both | The 5151 has '''no mains cord of its own'''. It takes both signal and power from the system unit: the signal cable comes from the display adapter, and a second cable takes ac power from a non-standard switched socket on the rear of the PC's power supply, so the system unit's power switch controls the display.<ref name="oa5151" /> That outlet supplies a maximum of 0.75 A and IBM states it is intended only for this display.<ref name="tr5150">IBM, ''IBM 5150 Technical Reference'' — hosted on this wiki as [[:File:IBM PC 5150 Technical Reference.pdf]] and documented as [[IBM PC 5150 Technical Reference]]. Section 1 "System Board" for the ROM and RAM subsystems; Section 3 "Power Supply", pages 3-3 to 3-6, for the 63.5 W continuous rating, the four dc outputs and their load and regulation figures, the −5 V dynamic-memory bias role, the switched 0.75 A ac outlet provided only for the IBM Monochrome Display, the overvoltage and overcurrent behaviour, the five-second minimum off time and the under- and over-voltage sense levels; Section 4 "Keyboard" for the capacitive keyboard, its Intel 8048, the permanently attached coiled five-wire cable, the 83-key layout, the scan-code protocol and the keyboard's own power-on self test.</ref> | ||
Two models were | Two models were built, a 110 Vac model and a 220/240 Vac model, and IBM's ''Options and Adapters'' section carries a separate full schematic for each.<ref name="oa5151" /> | ||
== Input Connector == | == Input Connector == | ||
| Line 69: | Line 69: | ||
* '''Stiff brightness and contrast knobs.''' Known behaviour on a healthy 5151, and probably deliberate. Not a fault.<ref name="mz5151" /> | * '''Stiff brightness and contrast knobs.''' Known behaviour on a healthy 5151, and probably deliberate. Not a fault.<ref name="mz5151" /> | ||
* '''Stable raster with the brightness turned up, but no characters.''' On a 5151 specifically, a stable raster proves the monitor is receiving correct horizontal and vertical sync from the MDA card. Work through: contrast set too low; a faulty MDA card | * '''Stable raster with the brightness turned up, but no characters.''' On a 5151 specifically, a stable raster proves the monitor is receiving correct horizontal and vertical sync from the MDA card. Work through: contrast set too low; a faulty MDA card generating sync but no video; an open video wire in the cable; a poor connection on pin 7 at the plug; then the video path inside the monitor. '''IC201, an SN7406A, has been reported failed by more than one owner.'''<ref name="mz5151" /> | ||
* '''No display at all, not even a raster.''' The 5151 needs an incoming horizontal sync signal from a working, initialised MDA card to produce any raster at all. Before condemning the monitor, check that the card is present, seated and initialised — motherboard switch settings that select EGA instead of MDA | * '''No display at all, not even a raster.''' The 5151 needs an incoming horizontal sync signal from a working, initialised MDA card to produce any raster at all. Before condemning the monitor, check that the card is present, seated and initialised — motherboard switch settings that select EGA instead of MDA leave it uninitialised.<ref name="mz5151" /> | ||
* '''Full or partial vertical collapse.''' A known symptom with | * '''Full or partial vertical collapse.''' A known symptom, with circuit diagrams and expected waveforms published for the vertical deflection stage.<ref name="mz5151" /> | ||
* '''Bright spot or line when switching off.''' Known behaviour, not a fault.<ref name="mz5151" /> | * '''Bright spot or line when switching off.''' Known behaviour, not a fault.<ref name="mz5151" /> | ||
* '''Dim or shrunken raster, or geometry that drifts as the set warms up.''' Points at ageing electrolytics on the analogue board. See [[Capacitor Failure Symptoms]]. | * '''Dim or shrunken raster, or geometry that drifts as the set warms up.''' Points at ageing electrolytics on the analogue board. See [[Capacitor Failure Symptoms]]. | ||
| Line 77: | Line 77: | ||
=== A self-inflicted fault worth knowing about === | === A self-inflicted fault worth knowing about === | ||
Because of the way the 5151 is designed, '''an improper horizontal sync signal can damage it''' — and software alone is enough to produce that situation by reprogramming the 6845 on the MDA card outside MDA timings.<ref name="mz5151" /> Do not run 6845 timing experiments | Because of the way the 5151 is designed, '''an improper horizontal sync signal can damage it''' — and software alone is enough to produce that situation, by reprogramming the 6845 on the MDA card outside MDA timings.<ref name="mz5151" /> Do not run 6845 timing experiments or untested display software against a 5151 you care about. | ||
== CRT Safety == | == CRT Safety == | ||
Revision as of 03:19, 23 September 2026
| IBM Monochrome Display | |
|---|---|
 |
|
| IBM monitors, left to right: 5151 monochrome, 5153 colour, 5154 Enhanced Color 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 |
The IBM 5151, which IBM called simply 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 80 × 25 text only — it has no graphics capability — but the MDA's large 9 × 14 character box gives an image of 720 by 350 addressable dots, which is why MDA text is visibly sharper than CGA text.
Display Characteristics
IBM's own figures:[1]
- CRT: 28.3 cm (11.5 in) diagonal, 90° deflection.
- Phosphor: P39, high persistence, green. Long persistence suppresses flicker at the 5151's low refresh rate, at the cost of smearing on moving content.
- Screen surface: etched to reduce glare.
- Presentation: 80 characters wide by 25 rows deep, each character defined in a 14 PEL high by 9 PEL wide matrix.
- Vertical drive: screen refreshed at 50 Hz, with 350 lines of vertical resolution and 720 lines of horizontal resolution.
- Horizontal drive: positive-level, TTL-compatible, at 18.432 kHz.
- Video bandwidth: 16.257 MHz maximum at −3 dB.
- Heat output: 325 BTU/hr. Power cable 0.914 m, signal cable 1.22 m.
Measured at the adapter, MDA horizontal sync is an 8 µs positive-going pulse every 54.3 µs and vertical sync is an 850 µs negative-going pulse every 20 ms.[2]
The 5151 will not work with a CGA card: CGA scans horizontally at 15.75 kHz, well outside the 5151's fixed 18.432 kHz.[2]
Power
The 5151 has no mains cord of its own. It takes both signal and power from the system unit: the signal cable comes from the display adapter, and a second cable takes ac power from a non-standard switched socket on the rear of the PC's power supply, so the system unit's power switch controls the display.[1] That outlet supplies a maximum of 0.75 A and IBM states it is intended only for this display.[3]
Two models were built, a 110 Vac model and a 220/240 Vac model, and IBM's Options and Adapters section carries a separate full schematic for each.[1]
Input Connector
A 9-pin D-shell at standard TTL levels — 0.0 to 0.6 Vdc at down level, +2.4 to 3.5 Vdc at up level.[4]
| 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 being physically absent from the plug is normal, not damage — they are unused in the MDA standard.[5]
The display's three brightness levels (off, normal, bright) come from the combination of the Video and Intensity lines, not from an analogue video level.[4]
Common Faults
- Stiff brightness and contrast knobs. Known behaviour on a healthy 5151, and probably deliberate. Not a fault.[5]
- Stable raster with the brightness turned up, but no characters. On a 5151 specifically, a stable raster proves the monitor is receiving correct horizontal and vertical sync from the MDA card. Work through: contrast set too low; a faulty MDA card generating sync but no video; an open video wire in the cable; a poor connection on pin 7 at the plug; then the video path inside the monitor. IC201, an SN7406A, has been reported failed by more than one owner.[5]
- No display at all, not even a raster. The 5151 needs an incoming horizontal sync signal from a working, initialised MDA card to produce any raster at all. Before condemning the monitor, check that the card is present, seated and initialised — motherboard switch settings that select EGA instead of MDA leave it uninitialised.[5]
- Full or partial vertical collapse. A known symptom, with circuit diagrams and expected waveforms published for the vertical deflection stage.[5]
- Bright spot or line when switching off. Known behaviour, not a fault.[5]
- Dim or shrunken raster, or geometry that drifts as the set warms up. Points at ageing electrolytics on the analogue board. See Capacitor Failure Symptoms.
A self-inflicted fault worth knowing about
Because of the way the 5151 is designed, an improper horizontal sync signal can damage it — and software alone is enough to produce that situation, by reprogramming the 6845 on the MDA card outside MDA timings.[5] Do not run 6845 timing experiments or untested display software against a 5151 you care about.
CRT Safety
The 5151's CRT retains a lethal anode charge after the set is switched off and unplugged, and its mains-derived circuitry sits at line potential while it is running. Discharge the tube before working inside it — see CRT Discharge Procedure.
References
- ↑ 1.0 1.1 1.2 IBM, IBM Monochrome Display, Options and Adapters section, Personal Computer Hardware Reference Library — hosted on this wiki as File:IBM Options and Adapters - IBM Monochrome Display (5151).pdf. "Description" and "Specifications": the two-cable arrangement with power taken from the system unit, the 28.3 cm (11.5 in) diagonal 90-degree-deflection CRT, P39 high-persistence green phosphor with an etched anti-glare surface, 80 characters by 25 rows in a 14 PEL high by 9 PEL wide matrix, maximum video bandwidth 16.257 MHz at −3 dB, 50 Hz vertical refresh with 350 lines vertical and 720 lines horizontal resolution, positive-level TTL horizontal drive at 18.432 kHz, and the physical specifications quoted here. Also documented here as IBM Options and Adapters - IBM Monochrome Display.
- ↑ 2.0 2.1 IBM: MDA / CGA / EGA, minuszerodegrees.net. Source for the side-by-side 9-pin assignments and for the measured sync pulse shapes: MDA, an 8 us positive-going horizontal pulse every 54.3 us and an 850 us negative-going vertical pulse every 20 ms; CGA, a 4 us positive-going horizontal pulse every 63.7 us and a 190 us positive-going vertical pulse every 16.7 ms.
- ↑ IBM, IBM 5150 Technical Reference — hosted on this wiki as File:IBM PC 5150 Technical Reference.pdf and documented as IBM PC 5150 Technical Reference. Section 1 "System Board" for the ROM and RAM subsystems; Section 3 "Power Supply", pages 3-3 to 3-6, for the 63.5 W continuous rating, the four dc outputs and their load and regulation figures, the −5 V dynamic-memory bias role, the switched 0.75 A ac outlet provided only for the IBM Monochrome Display, the overvoltage and overcurrent behaviour, the five-second minimum off time and the under- and over-voltage sense levels; Section 4 "Keyboard" for the capacitive keyboard, its Intel 8048, the permanently attached coiled five-wire cable, the 83-key layout, the scan-code protocol and the keyboard's own power-on self test.
- ↑ 4.0 4.1 IBM, IBM Monochrome Display and Printer Adapter, Options and Adapters section, Personal Computer Hardware Reference Library — hosted on this wiki as File:IBM Options and Adapters - IBM Monochrome Display and Printer Adapter.pdf. Source for the Motorola 6845 CRT controller, the 4 KB display buffer with no parity, the two-bytes-in-553 ns fetch giving 1.8 MB/s, the 8 KB character generator holding 256 codes, the 9 PEL by 14 PEL character box carrying a 7 PEL by 9 PEL character, the 18 kHz monitor requirement, the statement that the adapter does not support a light pen with a P39-phosphor display, the register map, the 9-pin connector pin assignments and TTL signal levels, and the printer-adapter half with its 12 latched outputs and 5 steady-state inputs. Also documented here as IBM Options and Adapters - IBM Monochrome Display and Printer Adapter.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 IBM 5151 — Known Problems/Issues, minuszerodegrees.net. Source for the stiff brightness and contrast controls being normal, the raster-but-no-video diagnosis, the reported IC201 (SN7406A) failures, the vertical collapse and switch-off bright line notes, the statement that pins 3, 4 and 5 are absent from the connector by design, and the warning that an improper horizontal sync signal can damage the 5151.
Related Pages
- 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's own specification, hosted here
- CRT Discharge Procedure · Capacitor Failure Symptoms