| 17-JUN-1987 OSUNY files, how to build a blue box
BLUE BOX CONSTRUCTION AND TROUBLESHOOTING:
This bulletin has been taken from the OSUNY files from 82/83
This bulletin will deal only with the basic contruction, troubleshooting and
adjustment of the blue box. If you would like to know the specific job of any
part in the circuit just write me a msg and I will be glad to answer it.
We all know that the touch tones frequencies are composed of two tones (Two
different freqs.) so that is the reason why we have 2 VCO'S (Voltage
controlled oscilators). We will call these VCO#1 and VCO#2. If you have
noticed VCO#1 and VCO#2 are exactly the same type of circuits. That is why
only one was drawn. But remember that whatever goes for VCO#1 also goes for
VCO#2. Both VCO'S are composed of a handfull of parts. one chip two capacitors
2 resistors and five potentiometers. All of this will give you (when
properly calibrated) one of the freqs. necessary (the other one will come
from VCO#2) for the operation of the BB. Both of these freqs. will be mixed
in the speaker thus forming the required tone.
This is one of the most sophisticated designs I have ever made. Why?. because
other designs will drain the battery after 10 - calls! This design will make
them last 10 months!!!!!!. But never the less don't forget to put in a
switch for on and off. Ok let's build the two VCO'S and calibrate the unit
before we get to the keyboard contruction.
VCO CONTRUCTION
=== ===========
TOOLS REQUIRED
1 ocilliscope (recomended but not re quired)
1 Freq. counter (REQUIRED)
1 Volt meter " " "
Electronics tools (Pliers,drill, screwdrivers, etc)
PARTS
R1 1.5K RESISTOR 5%
R2 1K RESISTOR 5%
C1 .1uf ELECTROLYTIC CAPACITOR 16VDC
C2 .01uf ELECTROLYTIC CAPACITOR (MYLAR) 16VDC
IC1 2207 VCO CHIP BY EXAR ELECTRINICS
remember the above it is only for VCO#1 but the same goes for VCO#2.
R3-R4 150 OHM RESISTORS 5%
C3-C4 .1 uf ELECTROLITIC CAPACITOR 10VDC
P1-P10 200K TRIMMER POT - 20 TURNS
DIODES USED IN THE KEYBOARD ARE 1N914 TYPE (40 OF THEM)
AND 13 SWITCHES FOR THE KEYBOARD SPST. MOMENTARY.
SPKR= YOU CAN USE A TELEPHONE SPEAKER FOR THIS (IT WORKS BEST)
BUT REMEMBER TO TAKE OUT THE DIODE THAT IS CONNECTED
ACCROSS IT.
****************************************************************
IMPORTANT NOTES
1 DO NOT USE ANYTHING ELSE THAN A MYLAR CAPACITOR FOR C2
2 PINS 10,9,8 SHOULD BE TIED TOGETHER AND BE LEFT FLOATING.
3 ALL RESISTOR SHOULD BE 5%! NOTHING ELSE
4 A TELEPHONE SPEAKER GIVES THE BEST RESULTS
*****************************************************************
TROUBLE SHOOTING
By now you should have constructed the two VCO'S on a bread board or anything
that please s you.
Check for cold solder joints, broken wires, polarity of the battery,
etc.........
Before we apply power to the VCO'S we have to adjust the pots for their half
way travel point. This is done by turning them 21 turns to the right and then
10 turns to the left. Do the same for all ten of them.
Now apply power to the unit check to see that you have power in the chips by
putting the positive lead of your volt meter on pin 7 and the negative lead
on pin 12. If you don't have anything there turn off the unit and RECHECK
THE WIRING.
When you get the right voltages on the chips, connect a diode to a piece of
wire (look at fig. 2 for the orientation of the diode) from ground to any pot
at point T (look carefully at the schematic for point T it is labeled T1-T10
for all pots) You shold be able to hear a tone, if not dissconnect the lead
and place the speaker close to your ear and if you hear a chirp like sound,
this means that the two VCO'S are working if you don't, it means that either
one or both of the VCO'S is dead. So in this case it is allways good to have
an ocilloscope on hand.
Disconnect the speaker from the circuit and hookup the ocilliscope to one of
the leads of the speaker and the ground from the scope to the ground of the
battery. Connect again the ground lead with the diode connected to it from
ground to any pot on the VCO that you are checking and you should see a
triangle wave if not turn the pot in wich you are applying the ground to
until you see it. When you do see it do the the same for the other VCO to
make sure it is working. (a mplitude is about 2VAC)
When you get the two VCO'S working you are set for the adjustment of the
individuals pots...
ADJUSTMENT
Disconnect the speaker from the circuit and connect a freq. counter (the
positive lead of the counter to one of the speakers leads that belongs to
VCO#1 or connect it to pin 14).
Connect the negative lead to the battery negative and connect the jumper
lead with the diode from ground to pot number 1 T1 .( The first pot number 1
point T1) If you got it working you should hear a tone and get a reading on
the counter. Adjust the pot for a freq. of 1700hz and continue doing the
same for pots 2-5 except that they get differents freqs.
Now disconnect the freq. counter from the speaker lead of VCO#1 or from pin
14 (which ever you had it attached to at the beginning) and connect it to the
speaker lead of VCO#2 or to pin 14 of VCO#2 and perform the same adjustments
to P6-10.
When you finish doing all of the pot go back and recheck them again.
KEYBOARD
If you look at fig-2 you will see that the keys are simple switches connected
to ground and two diodes on the other end. These diodes are used to simplify
the construction of the keyboard because otherwise the distribution of the
ground signal for both VCO'S would have been done mechanically. One diode
will go to VCO#1 and the other will go to VCO#2. Fig-3 shows the arrangement
of the keys on the keyboard.
Below is a table that will help you connect the keys to required
VCO'S pots.
TO TO FREQ OUT FREQ OUT
KEY POT ON VCO1 POT ON VCO2 PIN 14 VCO1 PIN 14 VCO
C 1 6 1700 1100
0 2 10 1300 1500
E 1 10 1700 1500
1 4 7 900 700
2 3 7 1100 700
3 3 8 1100 900
4 2 7 1300 700
5 2 8 1300 900
6 2 6 1300 1100
7 5 7 1500 700
8 5 8 1500 900
9 5 6 1500 1100
X - 9 ---- 2600
***********************************************************************
* REMEMBER THAT FIG-2 IT IS THE SAME FOR EACH KEY EXCEPT THE "X" WHICH*
* ONLY TAKES ONE DIODE. *
***********************************************************************
As a final word you can build this in any type of enclosure and should never
be used to make free calls using the telephone lines. I hope this bulletin
will clear any question you may had on the blue boxes.
If you have any question please
leave me a msg. and I will be very glad to
answer it.
TXS
MR. AMERICA
Ps. I would like to thank my keyboard, my fingers, and me for helping me
writte this bullettin. Without their help I would have never finish this
project.
BLUE BOX SCHEMATICS:
This bulletin has been taken from the OSUNY files from 82/83
PLEASE NOTE THAT THIS BULLETIN IS FOR IN FORMATION PURPOSES
ONLY AND YOU SHOULD NOT ATTEMPT TO BUILD THIS DEVICE FOR
USE IN ANY FRAUDULENT OR ILLEGAL ACT.
M R. AMERICA
KEY
===
First a few KEYS to the diagram:
Cx is capacitor #x Denoted by: ---! !---
Px is Pot or Variable resistor #x Denoted by : /
\
/<--
\
Rx is resistor #x Denoted by /\/\/\/\
SCHEMATICS
==========
The XR-2207 chip is a Voltage-Contr olled Oscillator and a 14
pin device thu s you must be very careful when soldering
the parts to this device. It is a little dificult to actually draw a
schematic on a 80 character scren using limited gra phics but will
give it a try.
This is a diagram of how to locate the different pins on the chip please
notice that pin one is the closest to the notch on top of the chip. The
first thing we'll do is to connect power to the chip (remember that you
need to build two of these to get a complete system) this is accomplished by
connecting the positive wire of the battery lead to pin 1 one leg of R1 and R2
is solder to pin 11 the other leg of R1 goes to pin 1 or to the positive of
the battery. The other leg of R2 goes to ground, C1 goes between pin 10
and ground.
The timing capacitor or C2 goes between pins 2 and 3 of the chip
pins 8 and 9 should be grounded to ground. Pin 14 is the output
and this is where one leg of C4 (C3 goes on the other VCO) in series with
R3(the same goes for the other VCO) and to one lead of the speaker.
The trimmer pots P1 to P10 should be grouped in groups of 5 pots each
the way you group it is by soldering one end of the pot to each other
leaving the wiper and the other end free.
