without "straining" the leads. Solder all three connections securely.
16. Install R12, 1K ohm
17. Install R9, 470 ohm (what colors were those?!)
18. Install C12, a 10 uF electrolytic capacitor. This component is "polarized" and must be oriented correctly before soldering. The positive or ( + ) points are clearly marked on the PC board layout diagram. Study the style and markings of the capacitors supplied in your kit. Generally, electrolytic capacitors indicate the negative, or ( - ) lead with a black edge strip or a ( - ) marking. Be alert about polarity throughout assembly!
19. Install Q1, a 2N3904 transistor. Be sure to face the flat side as shown in the diagram.
20. Install R7, 1K ohm resistor
21. Install C5, 10 uF electrolytic capacitor. Again, this component is polarized so check the parts layout for correct orientation.
22. Install jumper JMP2 (formed from a scrap component lead).
23. Install R5, 470 ohm
24. Install C14, a .01 uF disc capacitor (marked .01 or 10 nf or 103).
25. Install U2 the LM380 audio amplifier IC. Notice that one end of the chip is marked with a notch, dot, or band. Check the parts diagram for correct placement. Before soldering, ensure all pins have made it through the board. (It’s not much fun removing a chip because one pin is bent under!)
26. Install C15, a 1000 uF electrolytic capacitor. Be sure to orient it correctly, as electrolytic caps can explode if installed backwards! This capacitor acts to filter the supply voltage for noise free audio.
27. Install capacitor C10, the
28. Install C13, a .1 uF disc capacitor (marked .1 or 104).
29. Install R13, 2 ohm
30. Install J4, the 3 pin header strip. Later we’ll use a small jumper block to enable switching between line or speaker level audio output without having to remove and resolder jumpers.
31. Install jumper JMP4.
You’ve just completed the output paths for both the TX and RX portions of the circuit. Take a break and recheck your work. It’s also a good time to take a look at the schematic diagram and follow through what we’ve done.
Moving on, we'll build the "heart" of your scrambler unit, containing the MX128 IC and associated components. Since the majority of the work is