Ramsey Electronics HR40 manual ˆ17. Install R5, 10k ohms brown-black-orange

capacitor is a first step in setting up the resonant frequency of the SA602’s internal oscillator, using the resonant LC circuit to be created along with C1, C3 and L1.

ˆ12. Install C1, 100pF disc capacitor (marked 100 or 101K).

ˆ13. Install C3, .001µF disc capacitor (marked 102 or .001 or 1nF).

ˆ14. Install L2, shielded oscillator coil (marked K6883 or K6886).

ˆ15. Install C4, 100pFdisc capacitor (marked 100 or 101). C4 adds variable capacitance of the varactor tuning network to the oscillator circuit already formed by L2, C1, C2 and the SA602.

ˆ16. Install D1, the 1N4002 diode, making sure that the cathode or banded end is oriented towards the back of the PC board. This diode performs the function of a varactor diode. A varactor diode acts like a variable capacitor whose capacitance is controlled by the voltage across it. There is nothing fancy about the varactor diodes, so we are using a common rectifier diode as a varactor.

ˆ17. Install R5, 10k ohms (brown-black-orange)

ˆ18. Install R2, 10k potentiometer tuning control.

ˆ19. Install R3, 10k potentiometer volume control. This control varies the level of audio from pin 4 of the SA602 to the LM386 audio amplifier.

ˆ20. Using a scrap piece of wire, snipped from an installed component, install JMP-1. Jumpers are required sometimes in PC board layout to make a connection that has to cross over other PC-board traces.This particular jumper brings 9 volts from the power switch to the long circuit trace supplying voltage to the entire circuit. Notice how the jumper crosses over the other traces leading from the volume control.

ˆ21. Install S1, the power switch.

ˆ22. Install the 9-volt battery snap connector, making sure that the red (+) and black (-) leads are correctly installed.

ˆ23. Install C7, .01µF disc capacitor (marked 103 or .01 or 10nF).

ˆ24. Install C8, a small 4.7-10µF electrolytic capacitor. Observe correct polarity.

ˆ25. Install R6, 10K ohm resistor (brown-black-orange).

ˆ26. nstall U2, the LM386 audio amplifier IC chip. Just like the SA602, you must correctly position the notched or banded end.

ˆ27. Install C12, 100-220µF electrolytic capacitor; observe polarity. This capacitor couples the output of the LM-386 to the speaker jack.

ˆ28. Install C9, 4.7-10µF electrolytic capacitor; observe polarity.

HR40 • 12