MFJ-8100K Manual

Construction Phase 3 (Steps 3-1 through 3-20)
The following group of parts form the audio amplifier circuit which boosts the signal
from the FET transistors to useful listening volume.
3-1a. Examine the 8-pin socket for the LM386 IC and notice the rectangular notch
at one end. This notch should be oriented in exactly the same direction as
imprinted on the board (toward C14). Press the socket pins into their 8 holes
so that the socket rests flat on the board. You may wish to slightly bend two
or more pins after insertion so that the socket won't slip out.
3-1b. After making sure that all 8 pins are clearly visible on the bottom of the board,
solder each connection carefully. Be sure not to let the solder tip touch two
pins at the same time, which would cause unwanted "solder bridges".
3-2a. In step 2-3 above, you installed the first of the 5 electrolytic capacitors used in
the receiver. The remaining 4 are of this amplifier section. We'll install all of
them now, so that the importance of correct (+) and (-) positioning stays fresh
in mind.
3-2b. Install C19, 470µF per 3-2a (above).
3-3. Install C13, 100µF per 3-2a (above).
3-4. Install C14, 10µF per 3-2a (above).
3-5. Install C12, 22µF per 3-2a (above).
3-6. Before proceeding, please double-check the polarity correctness for all 5
electrolytic capacitor!
3-7. Install R11, 22 ohms (red-red-black).
3-8. Install R12, 15 ohms (brown-green-black).
3-9. Install C15, .1µF (marked 104Z).
3-10. Install C11, .1µF (marked 104Z).
3-11. Install C9, .0033µF (body marking 332K).
3-12. Install R9, 1K (brown-black-red).
3-13. Install C10, .1µF (marked 104Z).
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