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186 lines
8.4 KiB
Plaintext
186 lines
8.4 KiB
Plaintext
This bulletin has been taken from the OSUNY files
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This bulletin will deal only with the b asic contruction, troubleshooting and
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adjustment of the bl ue box. If you would like to know the specific job of a
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ny part in the circuit just write me a msg and I will b e glad to ans- wer it.
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We all know that the touch tones freque ncies are composed of two tones (Two
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different freqs.) so t hat is the reason why we have 2 VCO'S ( Voltage
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controlled oscilators). We will call these VCO#1 and VCO#2. If you have
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noticed VCO#1 and VCO#2 are exactly the same typ e of circuits. That is why
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only one was drawn. But reme mber that whatever goes for VCO#1 also goes for
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VCO#2. Both VCO'S are composed of a handfull of parts. one chip two cap
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acitors 2 resistors and five potentiometers. All of this wil l give you (when
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properly calibrated) one of the freqs. necessary (the other one will come
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from VCO#2) for the operation of th e BB. Both of these freqs. will be mixed
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in the speaker thus forming the required tone.
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This is one of the most sophisticated de signs I have ever made. Why?. because
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other designs will drain t he battery after 10 - calls! This design will make
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them last 1 0 months!!!!!!. But never the less don't forget to put in a
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switch for on and off. Ok let's build the two VCO'S and calibr ate the unit
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before we get to the keyboard contruction.
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VCO CONTRUCTION
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=== ===========
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TOOLS REQUIRED
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1 ocilliscope (recomended but not re quired)
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1 Freq. counter (REQUIRED)
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1 Volt meter " " "
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Electronics tools (Pliers,drill, scre wdrivers, etc)
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PARTS
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R1 1.5K RESISTOR 5%
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R2 1K RESISTOR 5%
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C1 .1uf ELECTROLYTIC CAPACITOR 16V DC
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C2 .01uf ELECTROLYTIC CAPACITOR (MYL AR) 16VDC
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IC1 2207 VCO CHIP BY EXAR ELECTRINI CS
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remember the above it is only for VCO#1 but the same goes for VCO#2.
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R3-R4 150 OHM RESISTORS 5%
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C3-C4 .1 uf ELECTROLITIC CAPACITOR 10VDC
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P1-P10 200K TRIMMER POT - 20 TURNS
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DIODES USED IN THE KEYBOARD ARE 1N914 TYPE (40 OF THEM)
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AND 13 SWITCHES FOR THE KEYBOARD SPST. MOMENTARY.
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SPKR= YOU CAN USE A TELEPHONE SPEAKER FOR THIS(IT WORKS BEST)
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BUT REMEMBER TO TAKE OUT THE DIO DE THAT IS CONNECTED
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ACCROSS IT.
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**************************************** ************************
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IMPORTANT NOTES
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1 DO NOT USE ANYTHING ELSE THAN A MYL AR CAPACITOR FOR C2
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2 PINS 10,9,8 SHOULD BE TIED TOGETHER AND BE LEFT FLOATING.
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3 ALL RESISTOR SHOULD BE 5%! NOTHING ELSE
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4 A TELEPHONE SPEAKER GIVES THE BEST RESULTS
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**************************************** *************************
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TROUBLE SHOOTING
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By now you should have constructed the two VCO'S on a bread board or anything
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that please s you.
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Check for cold solder joints, broken wi res, polarity of the battery,
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etc.........
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Before we apply power to the VCO'S we h ave to adjust the pots for their half
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way travel point. This is done by turning them 21 turns to the right and then
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10 turns to the left. Do the same for all ten of them.
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Now apply power to the unit check to see that you have power in the chips by
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putting the positive lea d of your volt meter on pin 7 and the negative lead
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on pin 12 . If you don't have anything there turn off the unit ant REC HECK
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THE WIRING.
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When you get the right voltages on the c hips, connect a diode to a piece of
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wire (look at fig. 2 for the orientation of the diode) from ground to any pot
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at point T (look carefully at the schematic for point T it is label ed T1-T10
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for all pots) You shold be able to hear a tone, if no t dissconnect the lead
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and place the speaker close to your ear and if you hear a chirp like sound,
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this means that the two VCO' S are working if you don't, it means that either
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one or both of the VCO'S is dead. So in this case it is allways good to ha ve
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an ocilloscope on hand.
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Disconnect the speaker from the circuit and hookup the ocilliscope to one of
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the leads of the speaker and t he ground from the scope to the ground of the
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battery. Connect ag ain the ground lead with the diode connected to it from
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grou nd to any pot on the VCO that you are checking and you should see a
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triangle wave if not turn the pot in wich you are appl ying the ground to
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until you see it. When you do see it do the the same for the other VCO to
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make sure it is working. (a mplitude is about 2VAC)
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When you get the two VCO'S working you a re set for the adjustment of the
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individuals pots...
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ADJUSTMENT
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Disconnect the speaker from the circu it and connect a freq. counter (the
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positive lead of the counte r to one of the speakers leads that belongs to
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VCO#1 or connect i t to pin 14).
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Connect the negative lead to the batt ery negative and connect the jumper
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lead with the diode f rom ground to pot number 1 T1 .( The first pot number 1
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point T1) If you got it working you should hear a tone and get a reading on
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the counter. Adjust the pot for a freq. of 1700hz and continue doing the
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same for pots 2-5 except that they get d ifferents freqs.
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P1= 1700hz
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P2= 1300hz
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P3= 1100hz
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P4= 900hz
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P5= 1500hz
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Now disconnect the freq. counter from t he speaker lead of VCO#1 or from pin
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14 (which ever you had it attac hed to at the beginning) and connect it to the
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speaker lead of VCO#2 or to pin 14 of VCO#2 and perform the same adjustments
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to P6-10.
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P6= 1100hz
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P7= 700hz
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P8= 900hz
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P9= 2600hz MAGIC NUMBER!!!!!
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P10= 1500hz
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When you finish doing all of the pot g o back and recheck them again.
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KEYBOARD
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If you look at fig-2 you will see that the keys are simple switches connected
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to ground and two diodes on th e other end. These diodes are used to simplify
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the construction of the keyboard because otherwise the distribution of the
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ground signal fo r both VCO'S would have been done mechanically. One diode
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will go to VCO#1 and the other will go to VCO#2. Fig-3 shows the arrangement
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of th e keys on the keyboard.
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Below is a table that will hel p you connect the keys to required
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VCO'S pots.
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TO TO FREQ OUT FREQ OUT
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KEY POT ON VCO1 POT ON VCO2 PIN 14 VCO1 PIN 14 VCO
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C 1 6 1700 1100
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0 2 10 1300 1500
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E 1 10 1700 1500
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1 4 7 900 700
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2 3 7 1100 700
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3 3 8 1100 900
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4 2 7 1300 700
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5 2 8 1300 900
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6 2 6 1300 1100
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7 5 7 1500 700
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8 5 8 1500 900
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9 5 6 1500 1100
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X - 9 ---- 2600
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**************************************** *******************************
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* REMEMBER THAT FIG-2 IT IS THE SAME FOR EACH KEY EXCEPT THE "X" WHICH*
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* ONLY TAKES ONE DIODE. *
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**************************************** *******************************
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As a final word you can build this in any type of enclosure and should never
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be used to make free ca lls using the telephone lines. I hope this bulletin
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will clear a ny question you may had on the blue boxes.
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If you have any question please
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leave me a msg. and I will be very glad to
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answer it.
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TXS
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MR. AMERICA
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Ps. I would like to thank my keyboard, my fingers, and me for helping me
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writte this bullettin. Wi thout their help I would have never finish this
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project.
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DOWNLOADED FROM P-80 SYSTEMS 304-744-2253
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