Re: Bi-color red/green LEDs: Disk II read/write?-- update

[Rubywand <rubywand@swbell.net>]

Rubywand wrote:
> 
> stephen e buggie writes ...
> >
> > A store is clearing out bi-color LEDs red/green.   These LEDs have three
> > wires:  black (negative), red (red +), green (green +).
> >
> > I want to add the bi-color LED to my Disk II drives, so that it will glow
> > GREEN for READ, and RED for WRITE. ....
> >
> 
>      Since the last post, there was a chance to do some experimentation.
> The circuit below seems to work well ...
> ....


     Below are a few additional notes for experimenters interested in
building the circuit.


Note: A good point for GND is pin 1 on the ribbon cable socket near the
back, left of the Disk ][ Analog Board. Pin 11-- the 6th pin on the
socket counting pin 1 as first-- is a good source for +5V. The pins--
actually, the bare leads from the socket going to the circuit board--
are shown below as viewed from the front of the Disk ][.


   1  3  5  7  9  11 13 15 17 19

   o  o  o  o  o  o  o  o  o  o

   |              |
  GND            +5V




Note: The new bi-color LED is installed in the hole left by removing the
old LED. (I just left the old LED connected.)   The mounting ring which
held the old LED did not fit well and tends to press the new LED's leads
together. I did not use the mounting ring. Epoxy (added from the back
after the LED is inserted) works well for holding the new LED in place.

Note: The 74121 IC was mounted on its back using epoxy in an open space
above the square cut-out in the circuit board. (Double-sided tape also
works well for 'dead-bug' mounting an IC.)  Pin 1 was marked with a dab
of white-out on the IC. 



Rubywand