Hammond Organ L-100 Series, Service Manual

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Page 21
of C608. The other plate of C608 responds by driving excess
electrons off to ground through resistor R624. The resultant posi-
tive voltage is then fed through D203 to the base of Q323, the
“Brush” gate. To the base of this “Brush” gate is also fed the noise
from the noise generator Q324. This noise is now tuned in the
collector circuit and fed to the “Cymbal and Brush” amplifier which
consists of Q325 and Q326.
2–7–5 CYMBAL KEYING
Anytime a pedal is depressed, the pedal signal is routed to the
pedal drawbar. A portion of this same signal is also fed to Q327
and 0328. These stages amplify and shape the signal and feed
it through R612 to the base of Q330, and through R613 and
Q205 to a R/C storage network and the base of Q329. The signal
developed across R616, the emitter resistor of Q330, is rectified
by Q204 and this posi tive voltage is applied to the base of Q33l,
the “Cymbal” gate, turning it on. At the same time, the output of
Q328 is being rectified by D205 and slowly applied to the base of
Q329. When Q329 is biased into conduction it depletes the base
bias nor mally supplied to Q330 through R612 and Q330 stops
conducting. In this state, no signal is available at the emitter or
Q330 to be rectified, and Q33l, the “Cymbal” gate, slowly turns off.
To the base of this “Cymbal” gate is also fed the noise from the
noise generator, Q324. This noise is tuned in the collector circuit
of Q331 and fed to Q325 and Q326, the “Cymbal and Brush”
amplifier.
2–7–6 BRUSH AND CYMBAL AMPLIFICATION
After being amplified by Q325 and Q326, the “Brush and Cymbal”
signals are routed to a voltage divider consisting of R604, R605,
and R606. It is then tapped by the switch and routed to R602,
the overall level control. This is located on a terminal strip on the
lower organ shelf, near the AO–43 amplifier. The wiper of the
overall level control (R602) now feeds into the AO–43 amplifier
through R601 and C318 to Pin 7 of V8. To enhance the “Brush and
Cymbal” effects, a small high frequency speaker is attached to the
main amplifier. It is located under the lower right hand end block on
the organ.
2–7–7 POWER SUPPLY
Power supply chassis is supplied with +340VDC from the
AO–43 amplifier. The +80 volts required for the percussion
assembly is obtained from voltage dividers R690 and R691.
+12VDC is obtained from Zener Diode D201.
2–8 L–100–1 SIX-VOICE PERCUSSION CIRCUITRY
2–8–1 POWER SUPPLY
(See Figure 5–5)
Power supply components are located in the power supply chassis
assembly (127–7 through –9). All necessary DC supply voltages for
the rhythm unit are supplied by this chassis. The output voltages
are 30VDC, 15VDC, and 5.5VDC. The 5.5V output is not used in
the Model L–100–1 organ.
120VAC 50/60 Hz is supplied to the power transformer from an
external source. The secondary AC voltage is 40VAC, which is
then bridge rectified by diodes D100, D101, D102, and D103. This
DC voltage is then filtered by the combination of R101, R103,
C100A, C101 and then applied across the 30VDC Zener diode
D104.
The 30VDC is the supply voltage for the amplifier stages Q106,
Q107 and Q108 on the rhythm PWB, and the reference voltage for
the 15VDC and 5.5VDC supplies. The 30VDC is supplied to the
voltage divider of R107 & R108 and fed to the voltage regulators
Q100 & Q102, the output of which is the 15VDC which is used to
supply all other circuits on the rhythm device.