Shown on this page is a schematic diagram (Figure A) of a master oscillator plus one frequency divider which is already mentioned on my techniques page. All the components shown within the red box make up the frequency divider. Five stages of frequency division need to be assembled for each one of the twelve master oscillators which together make seventy two oscillators. Seventy-three oscillators are normally needed for full sixty one note keyboards, but as I am publishing this project for the main aim of enhancing an existing set of tone generators, I am not worrying about the single oscillator needed for the lowest note. anyone wishing to use the circuitry in the construction of an organ simply needs to assemble a further oscillator. Each master oscillator with its five dividers is best assembled on its own separately etched printed circuit board. The transformer recommended for use is of the type used in transistor radios as audio driver transformers.  These may be purchased in the UK from a retail outlet such as Maplin and in the USA from Radio Shack. If difficulty is experienced in obtaining suitable transformers from a retail outlet then you will need to wind them yourself or have them wound for you. 

All fixed resistors used are 1/4 watt, C1 is the tuning capacitor which needs to be mica for high stability.

R6: the value needs to be  found by experimentation. If the value used is too low then frequency division will not occur.

Chris Rolph.

Webmaster, Theatre Organ Magic ©

Components List

R1: 47 K Ohms

R2: 33 K

R3: 2.2 K

R4: 270 K

R5: 270 K

R6: 3 - 20 K

R7: 33 K

R8: 3.3 K

R9: 270 K

C1: 1 - 5 Nanofarads

C2: 47 N

C3: 5 N

C4: 0.56 N

VR1: 3 K wirewound

VR2: 5 K miniature preset

TR1, TR2: BC108

 C5:

  Unit                    Div 1.            Div 2.            Div 3.           Div 4.         Div 5.

  C - G sharp       47 N             100 N            250 N          350 N         500 N

  G nat - D flat     100 N            250 N           500 N          1000 N      1,250 N

 C6:

  Unit                    Div 1.            Div 2.            Div 3.           Div 4.         Div 5.

  C - G sharp      0.56 N           1 N                4.7 N            10 N          100 N

  G nat - D flat    0.56 N            4.7 N            10 N             100 N        250 N

Figure B:                                   Figure C.

When the circuit boards are fully assembled they should be tested and pre-tuned on an auxiliary amplifier before finally connecting to the outputs of the organ's own master oscillator / frequency divider assemblies.

Figure D below is a suitable regulated power supply.  Add your own fuses!

Components List

R1: 5K6

R2: 3K3

C1: 1 microfarad electrolytic 35 V

C2: 1 microfarad electrolytic 35 V

C3: 220 N

C4: 1 microfarad

MAINS TRANSFORMER:12-15V

RECTIFIER: 

REGULATOR:

 78HO5 

TR1: BC477 

(useful hint: a suitable mains transformer may be found in a discarded hi-fi amplifier)