Vectronics VEC-1290K, Manual

Page 1: ...e suitable Vectronics reserves the right to make substitutions at any time In most cases these changes Defective Parts Today s electronic parts are physically and electrically resilient and defective components are rare However if you discover an item during your pre construction inventory that s obviously broken or unserviceable we ll replace it Just return the part to Vectronics at the address b...

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Page 3: ... legal under Part 15 of the FCC rules This Vectronics kit features a professional quality epoxy PC board with solder mask and silk screened parts legend to make assembly a breeze TOOLS AND Construction Area Kit construction requires a clean smooth and welllighted area where you can easily organize and handle small parts without losing them An inexpensive sheet of white poster board makes an excell...

Page 4: ... component lead or pad Solder bridges form when a trail of excess solder shorts pads or tracks together see Solder Tips below 4 Omitting or Misreading a Part This is easier to do than you might think Always double check to make sure you completed each step in an assembly sequence Soldering Tips Cleanliness and good heat distribution are the two secrets of professional soldering Before you install ...

Page 5: ...ime Enjoy Sorting and Reading Resistors The electrical value of resistors is indicated by a color code shown below You don t have to memorize this code to work with resistors but you do need to understand how it works When you look at a resistor check its multiplier code first Any resistor with a black multiplier band falls between 10 and 99 ohms in value Brown designates a value between 100 and 9...

Page 6: ...disc ceramic capacitors are marked with a three number code you may still find a 1 uF capacitor marked either 104 or 1 For three digit codes the first two digits indicate a numerical value while the last digit indicates a multiplier same as resistors The value is in pF thus a capacitor marked 104 is 100 000 pF or 1 uF Electrolytic capacitors are always marked in uF Electrolytics are polarized devi...

Page 7: ...ime Use this inventory as an opportunity to sort and arrange parts so you can identify and find them quickly Resistors Q Qty Part Description Designation 1 15 ohm brown green black R2 1 1K ohm brown black red R3 1 4 7K ohm yellow violet red R4 Capacitors Q Qty Part Description Designation 2 100 pF ceramic disc 101 C9 C10 1 510 pF polstyrene 510 C8 5 0 1 uF ceramic disc 104 C3 C4 C5 C6 C7 2 100 pF ...

Page 8: ...ion 1 DPDT push action switch SW1 1 RCA phono jack PC mounted J1 1 2 1 mm DC coaxial power jack J2 5 2 pin PC board mount headers JMP1 2 3 4 5 2 2 pin jumpers shorting 1 16 pin IC socket 1 8 pin IC socket 1 4 nylon cable tie 1 PC board 1 6 length of insulated 20 AWG solid wire ANTI PARTS PLACEMENT DIAGRAM ...

Page 9: ... bodies as close to the PC board as possible this is very important in RF circuits If you have last minute questions concerning what tools or materials are needed to assembly this kit please refer back to the section entitled BEFORE YOU BEGIN Install When you are directed to install a part this means to locate identify and insert the part into its mounting holes on the PC board This includes pre b...

Page 10: ...resistor at R2 on the printed circuit board 3 Solder and trim the leads 4 Find the 1K ohm brown black red 1 4 watt resistor 5 Install and solder at R3 6 Find the 4 7K ohm yellow violet red watt resistor 7 Install and solder at R4 resistor 9 Check each solder joint Look for solder splashes bridges a bridge is where solder has made a connection between two or more points that should not be connected...

Page 11: ...n inserting ensure that the three component leads are fully seated and that the capacitor body is level Install and solder at the following locations 11 C11 100 pF trimmer 12 C12 100 pF trimmer 13 Locate the 510 pF polystyrene capacitor This part may be marke 511 or with 510 using the old marking code system 14 Install and solder the 510 pF 510 or 511 polystyrene capacitor al C8 10 ...

Page 12: ...Install and solder at location L3 4 Locate the two 330 uH orange orange brown molded chokes Install and solder at locations 5 L4 330 uH orange orange brown 6 L9 330 uH orange orange brown 7 Locate the two 180 uH brown gray brown molded chokes Install and solder at the following locations 8 L5 180 uH brown gray brown 9 L6 180 uH brown gray brown and solder at the following 11 L7 100 uH brown black ...

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Page 14: ...n the circuit board and parts placement diagram If the markings on the capacitor body are unclear the plus lead is the longer of the two 1 Locate the two 10 uF electrolytic capacitors Install and solder at the following locations Observe the polarity markings 2 C1 10uF 3 C2 10 Phase 8 The Finishing Touches 1 Locate the IOK ohm vertical trimmer resistor Install at location RI Be sure the pot is ful...

Page 15: ... ALIGNMENT Before attempting any adjustments the entire section dealing with Alignment and Testing should be read and some familiarity with the Operating Instructions section is also advisable The transmitter requires a suitable external power and audio source for alignment and operation Initial alignment sets the transmitter to the desired operating segment of the AM broadcast band The VEC 1290K ...

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Page 17: ...metal objects If more range is needed try relocating the transmitter to a different location Once a clear channel has been found and the oscillator set to frequency the antenna matching network must be tuned Refer to Table 2 Note that some frequencies such as 800 kHz can be matched by one of two possible jumper configurations Try both and use the one which works best Using the previous example whe...

Page 18: ...s the pickup antenna Audio Gain Setting The VEC 1290K will accommodate a wide range of audio levels from line level cassette or CD deck feeds or even the very low output from a local mike Removing capacitor C2 will reduce the amplifier gain this is the preferred configuration for usually high line level audio sources such as when taking an audio feed directly from a speaker output Setting the gain...

Page 19: ...decks or even a local microphone for the budding DJ or talk show host Unless a single audio source is going to be used the audio gain control R1 will have to be continuously adjusted for each new audio source Tape decks and cassette players provide line level audio outputs for interconnections between decks and amplifiers Microphone produce much much lower signal levels As mentioned in the alignme...

Page 20: ... Part 15 rules permit a maximum field strength of 24000 fkHz uV per meter at 30 meters between 510 kHz and 1710 kHz The rules also permit a 100 mW transmitter with a ten foot antenna including the feedline In order to meet Part 15 regulations the transmitter output must be kept below 2 volts rms when using a 50 ohm antenna The high impedance antenna and power level of the VEC 1290K meet FCC Part 1...

Page 21: ...obvious mistakes What is needed is a fresh set of eyes Enlist a friend to go over your work Always check the obvious Is the power supply plugged in Is the power switch on Low range Check power supply voltage alignment of C11 and proper jumper configuration for antenna matching circuit Check antenna wire connection at ANTI on pc board Antenna not located in an optimum location Audio distorted Gain ...

Page 22: ... maximum modulation level of perhaps 25 to 30 percent Audio Amplifier and Modulator stage Low level microphone or line level audio is amplified by a LM386 audio amplifier IC The audio level to the IC is set by gain control R1 The output from the IC is directly applied to the RF power stage the 2N3904 transistor The DC output of the LM386 is normally at s of the supply voltage with no signal The DC...

Page 23: ...imum amount of inductance for segments of the AM band Trimmer capacitor C11 allows for a precise match at the operating frequency or maximum transfer of RF energy to the antenna The pi network is in essence is a low pass filter configuration and also offers some degree of harmonic energy rejection ...

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Page 25: ... edges and cut out the component holes g Repeat this procedure for the front panel 2 Next install the two L brackets on the chassis using two of the 3 16 screws The longer side of the L bracket must be connected to the chassis using the two holes centered on each edge of the enclosure Refer to the diagram on the next page for location and orientation 3 Install the four 1 2 mounting screws next Ins...

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