Vectronics VEC-1292K User Manual

VEC-1292K Owner’s Manual Stereo Transmitter Kit

INTRODUCTION

General Information: This nifty little transmitter will send your favorite tunes with you--throughout the house o r o ut i n the yard . W i sh your W a lkman CD player? No problem! Connect the VEC-1292K to your stereo's CD player and broadcast it to where you are. Can't pick up that distant FM station down in your basement shop? Simple! Connect the VEC-1292K to your stereo's FM tuner (the one with the big antenna), and rebroadcast the program on a clear channel. Thanks to the transmitter's specialized IC, you get true stereo with outstanding signal quality--just like FM radio stations generate from their studios. The uses are endless!

Circuitry: The VEC-1292K uses a sophisticated IC containing all of the circuitry needed for a miniature FM broadcast station. The audio stages, multiplex-stereo modulator, and transmitter RF section are all there--on one chip! The transmitter's sub-carrier oscillator is crystal controlled for rock-steady stereo lock-up on receivers. A channel balance control ensures perfect symmetry. It's even pre-emphasized for the 75 uS US-broadcast standard. The IC has everything you need to put a broadcast-quality stereo signal on the air in your own home. Operat ing fr eq ue ncy is inte r nall y adj ustab l e, and a tuned outp ut network matches the transmitter to a built-in collapsible antenna.

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TOOLS AND SUPPLIES

Construction Area: Kit construction requires a clean, smooth, and well-lighted area where you can easily organize and handle small parts without losing them. An inexpensive sheet of white poster board makes an excellent construction surface, while providing protection for the underlying table or desk. Diffused overhead lighting is a plus, and a supplemental high-intensity desk lamp is especially helpful for close-up work. Safety is always important! Use a suitable high-temperature stand for your soldering iron, and keep the work area free of clutter.

Universal Kit-building Tools: No special tools are required to complete this kit beyond common items normally used for bench construction. We recommend the following:

! Soldering iron (grounded-tip and temperature-controlled preferred) ! High-temperature iron holder with cleaning sponge ! Solder, 60/40 or 37/63 with rosin or "no-clean" flux (.031" dia. is good

size).

! Needle nose pliers or surgical hemostats

VEC-1292K Owner’s Manual Stereo Transmitter Kit

! Diagonal cutters or "nippy cutters" ! Solder sucker (squeeze or vacuum pump type), or desoldering braid ! Bright desk lamp ! Magnifying glass ! Insulated tuning tool set

BEFORE YOU START BUILDING

Experience shows there are four common mistakes builders make. Avoid these, and your kit will probably work on the first try! Here's what they are:

1. Installing the Wrong Part: It always pays to double-check each step. A 1K

and a 10K resistor may look almost the same, but they may act very differently in an electronic circuit! Same for capacitors--a device marked 102 (or .001 uF) may have very different operating characteristics from one marked 103 (or .01uF).

2. Installing Parts Backwards: Always check the polarity of electrolytic

capacitors to make sure the positive (+) lead goes in the (+) hole on the circuit board. ICs have a notch or dot at one end indicating the correct direction of insertion. Always double-check--especially before applying power to the circuit!

3. Faulty Solder Connections: Inspect for cold-solder joints and solder

bridges. Cold solder joints happen when you don't fully heat the connection-or when metallic corrosion and oxide contaminate a 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 d o 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 and solder each part, inspect leads or pins for oxidation. If the metal surface is dull, sand with fine emery paper until shiny. Allow the tip of your iron to contact both the lead and pad for about one second (count "one-thousand-one") before feeding solder to the connection. Surfaces must become hot enough for solder to flow smoothly. Feed solder to the opposite side of the lead from your iron tip--solder will wick around the lead toward the tip, wetting all exposed surfaces. Apply solder sparingly, and do not touch solder directly to the hot iron tip to promote rapid melting. Keep a damp sponge handy to wipe your so ldering tip on. This removes excess solde r, and

VEC-1292K Owner’s Manual Stereo Transmitter Kit

keeps the tip properly tinned. If the iron is going to sit idling for long periods, wipe the tip, add some fresh solder, and unplug the iron.

Desoldering Tips: If you make a mistake and need to remove a part, follow these instructions carefully! First, grasp the component with hemostats, needlenose pliers, or your fingers. Heat the pad beneath the lead you intend to extract, and pull gently. The lead should come out. Repeat for the other lead. Solder may fill in behind the lead as you extract it--especially if you are working on a double-sided b o ar d with plat e-thr o ugh hol es. Sho uld this ha pp e n, tr y heat ing the pad again and inserting a common pin into the hole. Solder won't stick to the pin's chromium plating. When the pad cools, remove the pin and insert the correct component. For ICs or multiple-pin parts, use desoldering braid to remove excess solder before attempting to extract the part. Alternatively, a lowcost vacuum-bulb or spring-loaded solder sucker may be used. Parts damaged or severely overheated during extraction should be replaced rather than reinstalled.

Work Habits: Kit construction requires the ability to follow detailed instructions and, in many cases, to perform new and unfamiliar tasks. To avoid making needless mistakes, work for short periods when you're fresh and alert. Recreational construction project are more informative and more fun when you take your time. 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:

Resistor Color Code

1st Digit 2nd Digit Multiplier

Tolerence

(gold or silver)

Black = 0 (tens) Brown = 1 (hundreds) Red = 2 (K) Orange = 3 (10K) Yellow = 4 (100K) Green = 5 (1Meg)

Blue = 6

Violet = 7

Gray = 8

White = 9

Silver = 10%

Gold = 5%

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 999 ohms. Red indicates a value from 1000 to 9999 ohms, which is also expressed as 1.0K to 9.9K. An orange multiplier band designates 10K to 99K, etc. To inventory resistors, first separate them into groups by multiplier band (make a pile of 10s, 100s, 1Ks, 10Ks, etc.). Next, sort each group by specific value (1K, 2.2K, 4.7K, etc). This procedure makes the inventory easier, and also makes locating specific parts more convenient later on during construction. Some builders find it especially helpful to arrange resistors in ascending order along a strip of double-sided tape.

VEC-1292K Owner’s Manual Stereo Transmitter Kit

Reading Capacitors: Unlike resistors, capacitors no longer use a color code for value identification. Instead, the value, or a 3-number code, is printed on the body.

Value Code

10 pF = 100 100 pF = 101 1000 pF = 102

.001 uF = 102*

.01 uF = 103 .1 uF = 104

Multilayer

(270 pF)

271

Ceramic Discs

(.001 uF) (.1 uF)

102

104

Electrolytic

1 uF

1uF

35V

As with resistors, it's helpful to sort capacitors by type, and then to arrange them in ascending order of value. Small-value capacitors are characterized in pF (or pico-Farads), while larger values are labeled in uF (or micro-Farads). The transition from pF to uF occurs at 1000 pF (or .001 uF)*. Today, most monolithic and disc-ceramic capacitors are marked with a three-number code. The first two digits indicate a numerical value, while the last digit indicates a multiplier (same as resistors).

Electrolytic capacitors are always marked in uF. Electrolytics are polarized devices and must be oriented correctly during installation. If you become confused by markings on the case, remember the uncut negative lead is slightly shorter than the positive lead.

Integrated Circuits: Proper IC positioning is indicated by a dot or square marking located on one end of the device. A corresponding mark will be silkscreened on the PC board and printed on the kit's parts-placement diagram. To identify specific IC pin numbers for testing purposes, see the diagram below. Pin numbers always begin at "1" at the keyed end of the case and progress along the device, as shown:

8 7 6 5

Installation

Key

1 2 3 4

Pin Numbers

Installation

Key

PARTS LIST

Your kit should contain all of the parts listed below. Please identify and inventory each item on the checklist before you start building. If any parts are missing or damaged, refer to the manual's warranty section for replacement

VEC-1292K Owner’s Manual Stereo Transmitter Kit

instructions. If you can't positively identify an unfamiliar item on the basis of the information given, set it aside until all other items are checked off. You may then be able to identify it by process of elimination. Finally, your kit will go together more smoothly if parts are organized by type and arranged by value ahead of time. Use this inventory as an opportunity to sort and arrange parts so you can identify and find them quickly.

Qty Part Description Designation VEC P/N

1 470 ohm resistor ( yellow-violet-brown) R8 100-2470

1 4.7K ohm resistor (yellow-violet-red) R6 100-3470

2 75K ohm resistor ( violet-green-orange) R4,R5 100-4750

1 150K ohm resistor ( brown-green-

! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

*One of these three values will be selected for use at C18--depending on desired frequency range.

yellow) 2 1K trimpot (102) R2,R3 135-3100 1 100K trimpot (104) R1 135-5100 2 10 pF multilayer capac itor (10 or 100) C13,C14 220-0010 2 15 pF multilayer capac itor (15 or 150) C15,C16 220-0015 1 22 pF multilayer capac itor (22 or 220) C18* 220-0022 1 27 pF multilayer capac itor (27 or 270) C18* 220-0027 1 33 pF multilayer capac itor (33 or 330) C18* 220-0033 1 220 pF multilayer capac itor (221) C17 220-0270 6 .001 uF multilayer capacitor (102) C6-C11 220-1100 2 10 uF electrolytic capacitor C3,C4 270-5100-1 2 22 uF electrolytic capacitor C1,C2 270-5220-1 1 100 uF electrolytic capacitor C5 270-6100-1 1 50 pF trimmer capaci tor C12 280-0050 1 .089 uH variable inductor L3 402-2706S 1 1 uH molded choke L2 401-3100 1 6” piece of magnet wire for L1 874-2422 3 1N4148 diode D1-D3 300-4148 1 BA1404 FM transmitter IC U1 325-1404 1 38 kHz crystal (small cylinder , 2 leads) Y1 405-0038 1 Miniature power switch, DPDT SW1 504-2022 2 RCA jack J1,J2 600-0011 1 18 pin socket for U1 625-0018 1 9V battery snap 730-3005 1 2” piece of insulated wire 871-24xx-0300 1 Telescoping antenna 758-1120 1 12mm metric scr ew 675-0012 1 Metric nut 706-3560 1 VEC-1292 printed circuit board 862-VEC1292

R7 100-5150

PARTS PLACEMENT

VEC-1292K Owner’s Manual Stereo Transmitter Kit

! ! 1. Find a 470 ohm resistor (yellow-violet-brown). Install at R8 and

solder. ! ! 2. Find a 4.7K ohm resistor (yellow-violet-red). Install at R6 and solder. Locate the two 75K ohm resistors (violet-green-orange).

! ! 3. Install a 75K at R4 and solder. ! ! 4. Install a 75K at R5 and solder. ! ! 5. Find the 150K ohm resistor (brown-green-yellow). Install at R7.

Next, install the kit's 12 multilayer capacitors. Avoid using force or excessive heat when installing these. If the spacing isn't right, pre-form leads to the correct spacing before inserting into the PC board.

Incorrect

Locate two (2) 10 pF multilayer capacitors (marked 10 or 100).

! ! 6. Install a 10 pF at C13. ! ! 7. Install a 10 pF at C14.

Locate two (2) 15 pF multilayer capacitors (15 or 150).

! ! 8. Install a 15 pF at C15. ! ! 9. Install a 15 pF at C16.

The next capacitor determines the frequency-tuning range of your FM transmitter. For the low end of the band, or 88-94 MHz, find the 33 pF capacitor (33 or 330). For the middle portion of the band, or 95-102 MHz, find the 27 pF capacitor (27 or 270). For 102 MHz and up, use the 22 pF capacitor (22 or

220).

! ! 10. Install the capacitor you've selected at C18 and solder. ! ! 11. Find a 220 pF multilayer capacitor (221). Install at C17 and solder.

Locate six (6) .001 uF multilayer capacitors (102).

! ! 12. Install a .001 uF at C6 and solder. ! ! 13. Install a .001 uF at C7 and solder.

Ooops!

Correct

! ! 14. Install a .001 uF at C8 and solder.

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