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IBM 5151  -  Power-Up


Unlike the 5151's successors, the 5153 (CGA) and 5154 (EGA), you will not see any display at all (not even a raster) if the 5151 is not connected to an operating MDA video card.  This is because of the design of the 5151.  For the high voltage (14 KV) to be generated, there needs to be a horizontal sync signal coming into the 5151.


If the 5151 has power alone, i.e. not connected to an operating MDA video card, operation of the 5151's components are as follows:

Component Operates            Comment
+15 Vdc out of power supply Yes  
+5 Vdc out of power supply Yes  
Other voltage sources No For this, the 5151 requires an incoming horizontal sync signal.
Vertical stage Yes Free runs if no incoming vertical sync signal.
Horizonal stage No For this, the 5151 requires an incoming horizontal sync signal.
CRT filament Yes Uses 15 Vdc out of power supply.  Diagram here.
14 KV generation for CRT No For this, the 5151 requires an incoming horizontal sync signal.


     
  xxxxxxx WARNING:

Opening the 5151 will expose you to dangerous voltages and currents.
Those threats can still be present long after power has been disconnected from the 5151.
Before opening the 5151, adequately educate yourself as to the hazards.
Hazard examples at here.