Advertisement
olated from the 16' - 8' - 4' signal by means of the 4. 7 K (251) resistor. The signal out of the
M Control for the IV Mixture will follow the same path as all the rest of the voices through the
Pre-Amplifier stage TR-8.
The vibrato section consists of a low frequency oscillator and an isolating buffer stage. Stage
TR-14 oscillates at approximately 6 cycles per second. The circuit components in the resistor/
capacitor network are chosen to assure dependable oscillation of this stage at this low frequency.
In addition, a regulated base bias voltage is taken from the emitter of TR -15 and wired through
resistor 206 to the base of the oscillator TR-14. This also assures stable oscillation. The out
put signal from the oscillator is taken from the collector of TR-14 and coupled through components
185 and 186 to the output base of buffer stage TR-13. This stage isolates the oscillator, and its
output from the collector through components 172 and 171 and appears across the load resistor
82K (183). The output across the resistor is then wired through a 100 K resistor to each base of
the twelve master oscillators in the generators. When vibrato is "OFF", this low frequency
signal line is shunted to ground through the vibrato switch. The vibrato switch, when "ON",
will affect the master oscillators causing them to swing sharp and flat to provide a smooth tonal
effect for all of the generated frequencies of the Combo Organ.
The +10 Volt DC regulated voltage out of the Zener used transistor TR-15 is also wired through
a 100 K resistor to each master oscillator base to help assure stable operation of these oscillators .
Power Supply - Part of Schematic No. 130716
The Power Supply is mounted on a separate chassis and is the unit providing regulated D. C .
Voltage for the Combo Organ.
A step-down power transformer having two isolated secondary windings is used. Silicon diodes
are used in a conventional rectifier configuration. The low voltage section taken out of diodes
D-1 and D-2 is filtered to ground by a large 10,000 mfd capacitor (241). The DC output is then
fed to two transistors TR-16 and TR-12 to provide extremely good +3 .45 Volts DC regulation.
This regulated voltage is used to operate the circuits within the IC 's found on the generator boards.
The higher voltage section taken out of diodes D-3 and D-4 is filtered by a two-section capacitor
l, 000 mfd. (239B) and l, 500 mfd. capacitor (239A). The DC output will follow two paths. One
path through the 47 ohm 2 watt resistor (240) +14.8 will be used to operate the master oscillator
and buffer transistors in the generator. The other path will be connected to two transistors TR -
11 and TR-10. These two transistors act as voltage regulators too provide a regulated DC voltage
of + 14. 5 V for all of the pre -amplifier transistors on the filter board and also the two active string
and bass filter stages. This voltage line is shown as point 8* on Schematic No. 130716.
In addition to the above three DC voltages, another voltage - +. 75 V is taken from a voltage di -
vider consisting of components 150 (18 K) and 142 (lK) filtered by capacitor 152 (175 mfd.). This
voltage is wired to all of the six group signal buss rods for the 16' - 8' -· 4' stops . Also this same
voltage +. 75 V,
will be found on the continuous mixture buss . The schematic shows this voltage
wired to these pomts through 1.8 K resistors. For example, the 16' first buss receives this vol
tage through component 210 (1 . 8 K). This +. 75 V DC will always be found on these buss rods to
assure smooth keying of the generator signal .
TOP
The combo top is held on by means of three screws and cup washers - one at each end and one in
the center back .
KEYBOARD ASSEMBLY
The entire keyboard assembly can be removed from the case as follows:
•
•
•
MAINTENANCE
Advertisement
