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555: Difference between revisions
elaboration of power supply interdependence
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The 555 uses special horizontal plug-ins that contain the trigger and sweep. Early instances of the 555 came with the 21 and 22 horizontal plug-ins. Later instances came with the 21A and 22A horizontal plug-ins, which use tunnel diodes for triggering. | The 555 uses special horizontal plug-ins that contain the trigger and sweep. Early instances of the 555 came with the 21 and 22 horizontal plug-ins. Later instances came with the 21A and 22A horizontal plug-ins, which use tunnel diodes for triggering. | ||
Regulation of the filament supply happens as follows: There is a feedback loop that is formed between the indicator | |||
unit and the power supply unit. The power supply sends AC through the interconnection cable to the indicator unit, | |||
where it is connected to the primary of the filament transformer. A sample of the output of the filament transformer is sent back through the interconnection cable from the indicator unit to the power supply unit. This performs two functions. First, the filament voltage that is sent back to the power supply unit is used to heat the cathodes of tubes in the power supply unit. Second, this filament voltage is the feedback signal to a regulator | |||
in the power supply unit that controls how much voltage is sent to the filament transformer. One of the consequences of this scheme is that it is impossible to energize the power supply unit without the indicator unit connected. The regulator tubes in the power supply would remain cold without filament power, and would not | |||
pass any current. | |||
* [http://bama.edebris.com/manuals/tek/555 555 manual on BAMA] | * [http://bama.edebris.com/manuals/tek/555 555 manual on BAMA] | ||