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specification sheets say the inverter (an LS04) can sink a current of 8mA maximum. I choose R to be 330 ohms as a good compromise between light output and sink current (see figure 1).

This is not quite the full story. The select line of bank 0 is treated as a special case and the output line of the decoder is first logically ANDed with the combined results of latch bits 6 & 7 and address line A15. The net result is that the LED indicator, as shown in figure 1, will be active (lit) whenever 32k page mode is selected. I have not found this any problem but purists may wish to use the ‘RO’ output at pin 13 of LB2 instead of select Line 0 as shown in Figure 1.

figure 1:circuit diagram

WIRING

The only components required are an LED and 330 ohm 1/8 or 1/4 watt resistor. The LED should be small (3mm) type but can be any colour, I just happened to have a red one to hand. Figure 2 shows the connections in both plan and frontal views.

1. Solder the 330 ohm resistor onto pins 9 and 14 on LB2 (component side) of card number 1.
2. Using single cored connection wire (wire wrapping cable is ideal) make the following connections on the underside of the board.
   

   LB1 pin 8 to LB2 pin 9
   

   LB1 pin 14 to LB2 pin 2

3. Carefully bend and crop the leads of the LED as shown in figure 2. Note that the LED is correctly orientated, the cathode end (flat on package) is free. Solder the anode to the positive pin of C46 on the component side of the board.
4. Now solder a length of single cored wire to the LED cathode (free end), then poke the wire through the plate through hole adjacent to IC7 as shown in figure 2. Solder the free end of the wire to LB2 pin 14. Since the final link involves the wire parsing through the hole, it is advisable to use wire that has a thick insulation layer, i.e. wire wrapping wire. If you plan to use enamelled wire, then I recommend you place a small piece of insulation over the wire and position it inside the hole. This will prevent the edges of the hole piercing the wire’s insulation.