---===<*> Building Of A Blue Box ! <*>===---
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 OSCILLATORS). 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
NEVERTHELESS 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 OSCILLOSCOPE (RECOMMENDED BUT NOT REQUIRED)
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 PLEASES 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 ANT 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 OSCILLOSCOPE 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
QUNTIL YOU SEE IT. WHEN YOU DO SEE IT DO THE THE SAME FOR THE
OTHER VCO TO MAKE SURE IT IS WORKING. (AMPLITUDE 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.
P1= 1700HZ
P2= 1300HZ
P3= 1100HZ
P4= 900HZ
P5= 1500HZ
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.
P6= 1100HZ
P7= 700HZ
P8= 900HZ
P9= 2600HZ MAGIC NUMBER!!!!!
P10= 1500HZ
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.
DBELOW 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.
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-CONTROLLED OSCILLATOR AND A 14
PIN DEVICE TH
US 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 GRAPHICS BUT WILL
GIVE IT A TRY.
TO GND_____________
]
___
C2 C3 ___
']]' ]
] ] _____]__9V+
] ] ] ]
' ' ' ' ' ' ' ]
------------------------------- ]
]7 6 5 4 3 2 1 ] ]
] < ]
]8 9 10 11 12 13 14] ]
------------------------------- ]
' ' ' ' ' ' ' ]
] ] ]
--] ]--------] ] ]
]C1 R2 ] R1 ]
GND ______]___/\/\/\/\______]_____/\/\/\/\______]
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 OUT PUT
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.
] THIS END GOES TO PIN 6 OF THE CHIP
]
_____________]_____________
/ / / / /
\ \ \ \ \
/<- /<- /<- /<- /<-
\ ] \ ] \ ] \ ] \ ]
/ ] / ] / ] / ] / ]
] ] ] ] ]
] ] ] ] ]
P1 P2 P3 P4 P5
AND FINALLY THIS IS THE WAY EACH KEY SHOULD BE WIRED.
DIODE
TO PX ------>]-----] THIS IS THE CONTACT OF THE KEY
]--------- \------
TO PX ------>]-----] ]
DIODE ]
-----
--- GROUND
-
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