Caple C871i Manual do Utilizador descarregar pdf (Página 93)

100

101

Apple II Computer Info

ring into parts box.

Spread apart retainer 'leaves' of LED mount (at back side of panel)

to permit easier insertion of new 3-lead LED.

Run LED + cable over back of board and along bottom toward the

hole in the front panel. Push through hole. (If hole is too small,

use a Dremel tool and steel 'bulb bit' to slightly enlarge front

part of hole.)

connect LED cable black to free end of Rcath

connect LED cable green to Emitter of Qgreen (right transistor)

connect LED cable red to Emitter of Qred.

position old LED cable beneath new LED cable.

connect a wire from the free end or Rgreen (on IC pin-1) to the

Base lead of transistor Qgreen.

connect a wire from the free end or Rred (on IC pin-6) to the

Base lead of transistor Qred.

Add epoxy to the back of the LED to secure LED in place

How it Works

When /Enable goes low to select the Drive, the power transistor

(Q1) switches ON and supplies +12V at its Collector. If there is no

Write, 74121 output /Q is high, Qgreen conducts, and the LED shows

Green. That is: the Green LED will light during boots and for any READs.

If the Drive is selected (/Enabled is low) and there is a Write

operation and Write Protect is not ON, then, the /Write Request signal

at 74LS125 pin 8 will go low. This triggers the 74121 One-Shot (at pin

3) producing an aprox. 160ms pulse at 74121 output Q. For the duration

of the pulse, /Q is low and Q is high. Qred conducts, and the LED shows

RED to indicate WRITE.

Rubywand

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Apple II Computer Technical Information : Apple II Family Hardware Info

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Caple C871i Manual do Utilizador Página 93

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