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49. Install R7, 2.2K ohm resistor (red-red-red). This part plays a role in
the keying of an attached radio. Depending on what type of microphone
your radio requires depends on whether or not this resistor is used. In all
of the Ramsey FX series transceivers and most handhelds, the resistor
is required. We'll look at this part later when we get to the
MICROPHONE CONSIDERATIONS section.
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50. Install R17, 2.2K ohm resistor (red-red-red).
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51. Install R20, 10K ohm resistor (brown-black-orange).
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52. Install C6, .01uF disc ceramic (marked .01 or 103 or 10nF).
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53. Install R24, 1K ohm resistor (brown-black-red). Notice that this
resistor stands upright.
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54. Install C10, 100pF disc capacitor (marked 100 or 101). This
component combined with R24 determines the clock speed of the
processor. If you power up the circuit later and you can see the displays
flickering, check these two components for correct installation.
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55. Install C7, 10uF electrolytic capacitor. Pay attention to polarity. This
is a DC blocking capacitor for the audio out of the ISD chip.
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56. Install U2, LM380 audio amplifier IC. Observe correct orientation of
the part.
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57. Install C2, 10uF electrolytic capacitor. Observe correct polarity. This
part couples external mike audio to the audio amplifier.
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58. Install R6, 10K ohm potentiometer (marked 103).
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59. Install R26, 2.2K ohm resistor (red-red-red).
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60. Install C4, .1uF disc ceramic capacitor (marked .1 or 104).
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61. Install R13, 2 ohm resistor (red-black-gold). This component
combined with C4 prevents U2 from going into high frequency
oscillations.
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62. Install C3, 220uF electrolytic capacitor. Pay attention to the polarity.
C3 is the audio output coupling capacitor.
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63. Install J2 and J3, both 1/8" mini jacks on the rear of the board. J2 is
the speaker output, J3 is the keyed mike input.
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64. Install J1, five pin DIN jack. This jack is where you may interface your
radio with the CB-1 voice recorder.
Congratulations! You have just completed construction of the main board.
CB-1 • 12
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