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IBM 5151  -  Known Problems/Issues


SYMPTOM:  Brightness and contrast knobs do not turn easily

A known behaviour.  IBM may have intended this.


SYMPTOM:  No video, but a stable raster shows if brightness turned up

If the brightness control is turned fully clockwise, a stable raster shows (example), but there is no video.
For the IBM 5151 (not other monitors), the stable raster informs us that the 5151 is receiving correct horizontal and vertical sync signals from the MDA video card.

Possible cause:	Contrast control set too low.
Possible cause:	Faulty MDA video card (generating sync signals, but not a video signal).  Try a known-working MDA card.
Possible cause:	Faulty cable (wire for video is open-circuit, either permanently, or intermittent).
Possible cause:	Pin 7 (video) within the 5151's DE-9 plug has poor/loose connection to the video card's DE-9 connector.
Possible cause:	A faulty component or connection somewhere in the video path within the 5151 - see here.  (Assuming raster present, video signal present, CONTRAST and BRIGHTNESS turned up.) A faulty IC201 (an SN7406A) has been reported by at least two people.

SYMPTOM:  No display (not even a raster)

Even if the brightness control is turned fully clockwise, no raster appears.  (Example of raster.)
Possibilities follow:

• Faulty 5151.

To get any display at all (including simply a raster), the 5151 requires that a horizontal sync signal is coming into the 5151 from an operating MDA video card.
Therefore, the following are possible causes as well:

• Not connected to an operating MDA video card.
• Poor connection to operating MDA video card.  Includes oxide build-up on connector pins, etc.
• Faulty MDA video card.
• MDA video card has not been initialised.  (Example cause: 5150/5160 motherboard switch settings set to EGA, instead of MDA.)  (Example cause: Faulty 5150/5160 motherboard.)


SYMPTOM:  Full or partial vertical collapse

An example of full vertical collapse is shown at here.  The circuit diagram of the 5151's vertical deflection circuitry is at here and here.


SYMPTOM:  Bright spot/line when turning off

An example photo of the line is at here.
This is known behaviour.
See the discussion at here.


Damage to 5151 from improper horizontal sync signal

Due to the design of the 5151, an improper horizontal sync signal (i.e. not conforming to MDA standard) can damage the 5151.

Even software can cause that situation.  Example at here.


Pins 3, 4, and 5 are missing from the 9-pin D connector

That is normal.  Pins 3, 4, and 5 are not used in the MDA standard (see here).