❒73. Install R16, 100K ohms
❒74. Install R15, 470K ohms
5. FINAL CONNECTIONS: THE LM386 AUDIO IC STAGE
You now have a working FM receiver ready for adjustment. The output of the MC3359 FM IC simply needs to be boosted to listening level. A few more connections, and your receiver will be ready for adjustment and testing! Now would be a good time to review some of your previous work and also to make sure you have on hand what you'll need for testing: antenna, fresh battery, earphone or speaker with correct plug or adapter.
❒75. Review the instructions for installing U1 and U2. Insert the LM386 IC (U3) with the band or dot oriented correctly. Solder the 8 connections.
❒76. Install C32, a 100 to 220 uF electrolytic, observe correct polarity.
❒77. Install C31, .01 uF (marked .01, 103, or 10 nF).
❒78. Install C36, 4.7 or 10 uF electrolytic, observe polarity.
❒79. Install C33, 100 to 220 uF electrolytic, observe polarity.
❒80. Install the battery snap terminal in the two holes below S1, making sure that the positive (red) lead is inserted into the (+) hole on the PC board.
❒81. The battery bracket may be attached in a variety of ways. A wire jumper can be passed through the two holes on the PC board, then both ends soldered on the underside of the board. You may prefer to use very small screws or even a
Wiring of the PC board is now complete. If you have the patience, we suggest a short break. Then take a magnifying lens and a bright light and examine all your solder joints, touching up any connection which appears less than perfect. Make sure all excess leads have been trimmed, and that one is not bent back flat against the board, possibly causing a short. Brush the solder side of the board with a stiff brush to make sure that no loose wire trimmings or solder drippings (tsk tsk) are lodged between connections.
FR146 • 17
