DÍA DE DIVERSIÓN EN FAMILIA

Before constructing your new 6N2 receiver, you will need to locate a clean well lit, well ventilated work space. Locate a small pencil tipped 27 to 33 watt soldering iron. You should also locate a spool of 22 ga. rosin core solder, a small container of “Tip Tinner” from your local Radio Shack store. “Tip Tinner” helps to clean and dress the soldering iron tip. Place the schematics and parts layout diagram in front of you along with all of the project components. A few small tools would be helpful to constructing your project, so find a small pair of end-cutters, a pair of tweezers, a magnifying glass, a small Phillips and flat-blade screwdrivers, and we can begin. When building a

project with integrated circuits it is wise to consider installing integrated circuit sockets on the PC board, as a form of insurance in the event of a possible circuit failure somewhere down the road. It is much more easy to simply unplug a damaged IC and simply replace it by plugging in a new one.

Before we get some momentum on the project, you may also want to refer to the chart in Table 12-2. This table lists the color codes for the resistors, and will greatly aide you in constructing the receiver. Go ahead and locate resistor R1, a 68 k resistor, its color code is (blue-gray-orange). Now locate resistor R2, a 47 k ohm resistor with (yellow-violet-orange) color code. Place these resistors on the circuit board in their respective locations and solder them in place. Now you can identify the remaining resistors and place them on the circuit board and solder them in their proper locations. Use your end-cutters to trim the excess component leads. Cut the extra component leads flush to the edge of the circuit board.

Now locate and install capacitors; first locate and identify capacitors C1 and C2. Capacitor C1 is a small disk capacitor marked (121) or120 pF. Small capacitors often do not have their actual values printed on them but use a three-digit code to represent their value. Refer to the chart in Table 12-3 to help you identify the small capacitors. Now look for capacitor C2, its value

Chapter Twelve: 6

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2-Meter Dual-Band Amateur Radio

Table 12-2

Resistor color code chart

Color Band 1st Digit 2nd Digit Multiplier Tolerance

Black 0 0 1 Brown 1 1 10 1% Red 2 2 100 2% Orange 3 3 1,000 (K) 3% Yellow 4 4 10,000 4% Green 5 5 100,000 Blue 6 6 1,000,000 (M) Violet 7 7 10,000,000 Gray 8 8 100,000,000 White 9 9 1,000,000,000 Gold 0.1 5% Silver 0.01 10% No color 20%

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2-Meter Dual-Band Amateur Radio

Table 12-3

Capacitance code information

This table is designed to provide the value of alphanumeric coded ceramic, mylar and mica capacitors in general. They come in many sizes, shapes, values and ratings; many different manufacturers worldwide produce them and not all play by the same rules. Some capacitors actually have the numeric values stamped on them; however, some are color coded and some have alphanumeric codes. The capacitor’s first and second significant number IDs are the first and second values, followed by the multiplier number code, followed by the percentage tolerance letter code. Usually the first two digits of the code represent the significant part of the value, while the third digit, called the multiplier, corresponds to the number of zeros to be added to the first two digits.

Value Type Code Value Type Code

1.5 pF Ceramic 1,000 pF /.001 µF Ceramic / Mylar 102 3.3 pF Ceramic 1,500 pF /.0015 µF Ceramic / Mylar 152 10 pF Ceramic 2,000 pF /.002 µF Ceramic / Mylar 202 15 pF Ceramic 2,200 pF /.0022 µF Ceramic / Mylar 222 20 pF Ceramic 4,700 pF /.0047 µF Ceramic / Mylar 472 30 pF Ceramic 5,000 pF /.005 µF Ceramic / Mylar 502 33 pF Ceramic 5,600 pF /.0056 µF Ceramic / Mylar 562 47 pF Ceramic 6,800 pF /.0068 µF Ceramic / Mylar 682 56 pF Ceramic .01 Ceramic / Mylar 103 68 pF Ceramic .015 Mylar 75 pF Ceramic .02 Mylar 203 82 pF Ceramic .022 Mylar 223 91 pF Ceramic .033 Mylar 333 100 pF Ceramic 101 .047 Mylar 473 120 pF Ceramic 121 .05 Mylar 503 130 pF Ceramic 131 .056 Mylar 563 150 pF Ceramic 151 .068 Mylar 683 180 pF Ceramic 181 .1 Mylar 104 220 pF Ceramic 221 .2 Mylar 204 330 pF Ceramic 331 .22 Mylar 224 470 pF Ceramic 471 .33 Mylar 334 560 pF Ceramic 561 .47 Mylar 474 680 pF Ceramic 681 .56 Mylar 564 750 pF Ceramic 751 1 Mylar 105 820 pF Ceramic 821 2 Mylar 205 1st Significant Figure 2nd Significant Figure Multiplier Tolerance CSGNetwork.Com 6/4/92 0.1µF 10% 104 k

is .005µF, but may be marked (502). Go ahead and install these capacitors in their respective locations on the circuit board. Remember to trim the excess component lead lengths with your end-cutters. Next, locate the remaining small capacitors and install them on the circuit board.

Next, we are going to locate and install the electrolytic capacitors. Electrolytic capacitors are generally larger in size and higher in value than the small value capacitors and usually they are vertical or horizontally mounted. Remember, electrolytic capacitors have polarity and must be installed with respect to this polarity if the circuit is going to work properly. The capacitor’s value will be printed on the body of the capacitor along with a white or black polarity marking, either a plus or minus marking. Pay attention to this plus or minus marking and align it with the proper holes on the PC board, you will have to refer to the schematic and or parts layout diagram when placing the electrolytic capacitors. Locate and install the remaining electrolytic capacitors onto the circuit board. Remember to trim the excess electrolytic capacitor leads after they are soldered in place.

In this project there are two silicon diodes. Diodes are generally rectangular in shape like a resistor but they are often clear glass or painted black. You will see a black or white band at one edge of the diode body, this marking denotes the diode’s polarity. The colored band is the diode’s cathode lead. When installing the diode make sure that you observe the polarity marking by referring to the parts layout and the schematic diagram. Polarity is important and must be observed in order for the circuit to work properly.

The 6N2 receiver has two crystal filters, a 455 kHz one and a 10.7 MHz one. These devices are small three-lead devices and look much like a small capacitor with three leads. Make sure that you can identify them properly before installing them on the circuit board. The 455 kHz unit connects to U1 at pins 5, 6 and 7, while the 10.7 MHz crystal filter is connected to pins 17, 18 and 19. The receiver also employs a single 10.24 MHz crystal which is connected between pins 4 and 6. This is a two-lead device and is usually a small metal can.

Now locate the air-wound coils L1 and L4. Coil L1 is 41_⁄

2turns of wire, it will be placed on the right edge of

the PC board, and coil L4, a 11_⁄

2turn air-wound coil, will

be mounted at the bottom center of the board. Coils L2 and L3 are 9 turn coils wound on a coil form with a ferrite tunable slug in the center of the form. Coil L5 is a 0.64 mH coil in a small metal can with five leads. Coil L5 is a tunable slug tuned coil with a yellow ferrite core, see Table 12-4 for coil winding details.

The 6N2 receiver utilizes three integrated circuits. Before we go ahead and install the integrated circuits, let’s take a brief look at the semiconductor pin-out diagram shown in Figure 12-6. The main receiver chip U1 is the Motorola MC3362, a 24 pin dual conversion FM receiver on-a-chip which contains oscillators, mixers, quadrature discriminator, and meter drive/carrier detect circuitry all in one chip. The audio amplifier at U2 is an LM386 chip, while U3 is 5 volt regulator, an LM78L05. When installing the integrated circuits, you will need to identify the pin-outs of each of the integrated circuits. It is advisable to install IC sockets prior to installing the ICs on the circuit board, to avoid the rare event of circuit failure at a late date. It is much easier to simply unplug an IC and insert another without un-soldering a 24 pin chip from the circuit board. Integrated circuits will generally have a small cut-out at one end of the IC package or a small indented circle at one end of the chip. Pin one (1) of the integrated circuit will be to the left of these markings. Be sure to orient the IC before placing into its proper socket. Note that pin 1 of U1 will connect to the junction of capacitors C7

and C16.

Chapter Twelve: 6

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2-Meter Dual-Band Amateur Radio

Table 12-4

Coil Winding Information

L1 4.5 turns insulated magnet wire - #22 ga. Air-core coil wound on 1_⁄

4′′form then remove coil.

L2, L3 81_⁄

2turns #24 ga. insulated magnet wire coil-wound

on 49A Series form - ferrite slug adjustable (49A127MPC) Circuit Specialists.

Remove original coil from form and rewind 81_⁄ 2turns.

L4 1.5 turns insulated magnet wire - #22 ga. Air-core wound on 1_⁄

4′′form then remove coil.

L5 .64 mH Coil (yellow) 455 kHz I-F Transformer Circuit Specialists - (42IF301).

Finishing the PC board