Pioneer PL-200 User manual

C)rqoNEEFr
RECEIVEDMAY ,, 88I
a This seruice manual describes the mechanical operations
and adjustments, and the D.D. motor employed in the
following models.
STEREO TURNTABLE
PLI elclcl
FL-ElcIcIX
PLI?55
PLISOO
PL-3clcIX
PLI 4ocl
FrL-4.clclx
PICINEEFI E-ECTFIONIC CCIFIFEIF|ATICIN 4-1. Mesu.o 1-chome. rvesuno-ku, Tokyo 153. Jap6n
lr.g. P|q\IEEF ELEST':EINICB OGIPCFIATION 85 Oxfotu O.,ve, Moonach,e, New Jereey O7O7A, U.S A:
PIChIEEFI ELECTFIO TIC (Et-FleEl N,V. Lurthagen-Haven g, 2OS AnEwerp, Elelgrum
PIO\|EEF| ELECTFIONICB AIJATFaALIA FYY. LTO. 178-184 E]ounda.y Road, Elnaesde, VcEonra 3195, AusE.6l6
<ART-467-0> r'@ocr. i979 Printed in Japan

CONTENTS
1. PL-200PANELFAClLlTlES... 3 7.4 OperationofthepA2004 lC(comparator
2. PL-255PANEL FAClLlTlES . .. 4 sontrol) . . .. .. . 16
3. PL-400 PANEL FACILITIES . . . 6 7.S Operation of the pA200b lC (drive
4. PL-300 PANEL FACILITIES . . . 8 sontrot) 1t
5. DISASSEMBLY 7.6 Btock diasram (pL-200, pL-25b) 21
5.1 Paneland base plate 9 g. MECHANTSM DESCR;pTIONS
5.2 D.D.motorandtonearm .......10 9.1 pL2ggmechanismoperating 22
6. PANEL AND BASE PLATE ASSEMBLY 8.2 pL-400 mechanicatoperation 24
6.1 PL-200,PL-300 .......11 9. ADJUSTMENT
6.2 PL-255,PL-400 .......12 9.1 Stylusdescentposition 28
7. CIRCUIT DESCRIPTIONS 9.2 Auto return adjustment 28
7 .1 Block diagram (PL-300, PL-400) 13 9.3 D.D. motor adjustment (PL-300 and
7.2 Motoroperation... 14 PL-400) .......29
7.3 Operation of the PD1003 lC (oscillator 9.4 D.D. motor adjustment (PL-200 and
stase). .......16 PL-255) 29

1. PL-2OO PANEL FACILITIES
BEFORE CONNECTING, CHECK THE
FOLLOWING:
o Switch the power to the amplif ier off to prevent damage
to the speaker system.
. The cartridge furnished with your turntable is an MM
type. Be sure to use a stereo amplifier which has PHONO
input.jacks for this type of cartridge.
NOTE:
lf you are using a low-output moving coil (MC) cartridge, you wilt
need a special MC transformer or a head amplifier, or a stereo
amplifier with a built-in MC amplif ier.
CONNECTION PROCEDURE
1. lnsert the phono cables (white and red) into the PHONO
input jacks of the stereo amplifier {white for left channel
into L jack, and red for right channel into R jack).
Platter/Rubber platter mat
Speed checking window
O speeo sELEcroR BUTToN
45 . . .. . . When this button is depressed, the platter
will rotate at 45rpm. Depress for playing 45
rpm records, singles or EP's.
33 . . . . . . When this button is set to the released posi-
tion, the platter will rotate at 33-1/3rpm.
Release for playing 33-1/3rpm records like
LP's.
o spreo ADJUSTMENT KNOB
Turn this knob when finely adjusting the speed of the
platter. The speed of platter will increase when the knob
is turned clockwise in the direction of "+"; it will de-
crease when turned counterclockwise in the direction of
2.
J.
Connect the ground lead with the Y-shaped connector
at the end to the ground terminal.
lnsert the power plug into the convehience AC outlet of
the amplifier or a wall outlet.
STEREO AMPLIFIER
Phono input jacks AC outlet
Power cord
Dust cover
Anti-skate knob
Arm rest
€) cuT BUTTON
lf this button is depressed while the record is playing, the
tonearm automatically returns to the arm rest, and the
power to the turntable is cut off.
@ ARM-ELEVATTON LEVER
UP ( ! ): When this lever is set to this position, the
tonearm will rise, Set it to UP before record
play and when you want to stop record play
while a track is being played or when you
want to change over to a dif{erent track.
DOWN (I ):When the lever is set to this position, the
tonearm will be lowered. lf it is set to
DOWN for record ptay, the tonearm will be
lowered onto the surface of the record, and
play will begin.
I
I
-l-.-.--
I
I
Ground lead

2. P1.255 PANEL FACILITIES

O srnnr/cur BUTToN
When this button is depressed, the power is turned on to
the turntable, the strobe light comes on and the platter
starts to rotate. With the RECORD SIZE SELECTOR
set at one of the positions - 30, 25,or 17 - the tonearm
moves automatically to the record disc as the platter starts
rotating, thus starting record play.
lf this button is depressed while the record is playing, the
tonearm automatically returns to the arm rest, and the
power to the turntable is cut of f .
@ REPEAT BUTToN
Push this button when you want to listen to the same re.
cord again. Press the button once more to release.
NOTE:
All you have to do for repeat play is to press the BE?EAT
button. There is no need to push the START/CUT button again.
@ REcoRD SIzE SELEcToR
This selector selects the size of the record for automatic
play.7"17. .. . For the automatic play of 17cm (7-inch)
LP and EP records.
10"25. . . . For the automatic play of 25cm (10-inch)
LP records.
12"30. . . . For the automatic play of 30cm (12-inch)
LP records.
@ SrnoeE LIGHT/SPEED cHEcKING WINDoW
This light comes on when the tonearm moves away from
the arm rest toward the platter. lt irradiates the strobo-
scope around the outside of the platter.
@ speeo ADJUSTMENT KNoB
Turn this knob when delicately adjusting the speed of the
platter. The speed of platter will increase when the knob
is turned clockwise, in the direction of "+"; it will de-
crease when turned counterclockwise, in the direction of
@ speeo
45..... SELECTOR BUTTON
When this button is depressed, the platter will
rotate at 45rpm. Depress for playing 45rpm
records, singles or EP's.
When this button is set to the release position,
the platter will rotate at 33-1/3rpm. Release
for playing 33-1/3rpm records like LP's.
€) TOruEARM
This tonearm is designed to apply the correct tracking
force to the cartridge and to keep this force at the precise
level for faithful tracking of the record grooves. lt also has
the job of switching the power on to the turntable.
a When the tonearm is moved from the arm rest to the
platter, the power comes on, the strobe lamp lights up,
and the platter rotates.
a When the tonearm is returned to the arm rest, the
power to the turntable is cut off, the strobe lightgoes
off, and the platter stops rotating.
@ anu-eLEVATtoN LEVER
UP(!): When this lever is set to this position, the
tonearm will rise. Set it to UP before re-
cord play and when you want to stop re-
cord play while a track is being played or
when you want to change over to a differ-
ent track.
DOWN ( t ): When the lever is set to this position, the
tonearm will be lowered. lf it is set to
DOWN for record play, the tonearm will
be lowered onto the surface of the record,
and play will begin.
E ANTI.SKATE KNoB
This knob is used to cancel out the harmful skating force
which is generated during record play.
@ NNU REST/cLAMPER
The arm rest supports the tonearm when it is not being
used. Set the tonearm on its rest when it is not playing re-
cords. Clamp it into position if you don't have any im-
mediate plans to play records.
O plnrrER/RUBBER pLATTER MAT
When the tonearm is moved and power is supplied to the
turntable, the platter will start rotating at the set rotation
speed. The rubber platter mat stabilizes the records and
also absorbs external vibration.
@ ousr covER
Keep this closed unless operating the controls or tonearm,
or changing over records. This serves to keep dust from
adhering to the records during record play. When fully
opened and pulled straight up, this dust cover can be re,
moved from the cabinet.
33

3. PL-4OO PANEL FACILITIES

O Srnnr/cuT BUTToN
When this.button is depressed, the power is turned on to
the turntable, the strobe light comes on and the platter
starts to rotate. With the RECORD SIZE SELECTOR
set at one of the positions - 30, 25, or 1 7 - the tonearm
moves automatically to the record disc as the platter starts
rotating, thus starting record play.
lf this button is depressed while the record is playing, the
tonearm automatically returns to the arm rest, and the
power to the turntable is cut off .
@ REPEAT BUTToN
Push this button when you want to listen to the same re-
cord again. Press the button once more to release.
NOTE:
All you have to doforrepeatplayisto presstheREPEAT button.
There is no need to push the START/CUT button again.
@ REcoRD srzE sELEcroR
This selector selects the size of the record for automatic
play.7"11 . .. . For the automatic play of 17cm (7-inch)
10"25 .
12"30.
LP and EP records.
. For the automatic play of 25cm (10-inch)
LP records.
. For the automatic play of 30cm (12-inch)
LP records.
@ STROBE LIGHT
This light comes on when the tonearm moves away from
the arm rest toward the platter. lt irradiates the strobo-
scope around the outside of the platter.
@ SPTCO SELECTOR BUTTON
45 . . .. . When this button is depressed, the platter will
rotate at 4Srpm. Depress for playing 45rpm
records, singles or EP's.
33 . . . . . When this button is set to the release position,
the platter will rotate at 33-1/3rpm. Release
for playing 33-1/3rpm records like Lp's.
@ roruEARM
This tonearm is designed to apply the correct tracking
force to the cartridge and to keep this force at the precise
level for faithful tracking of the record qrooves. lt also has
the job of switching the power on to the turntable.
a When the tonearm is moved from the arm rest to the
platter, the power comes on, the strobe lamp lights up,
and the platter rotates.
a When the tonearm is returned to the arm rest, the
power to the turntable is cut off, the strobe light goes
off, and the platter stops rotating.
e nnu-eLEVATIoN LEVER
UP (! ): When this lever is set to this position, the
tonearm will rise. Set it to UP before re-
cord play and when you want to stop re-
cord play while a track is being played or
when you want to change over to a diff er-
ent track.
DOWN ( Y ): When the lever is set to this position, the
tonearm will be lowered. lf it is set to
DOWN for record play, the tonearm will
be lowered onto the surface of the record,
and play will begin.
@ ANTI-SKATE KNoB
This knob is used to cancel out the harmful skating force
which is generated during record play.
For further details, see "ANTI SKATING ADJUST-
MENT".
O ARM REST/cLAMPER
The arm rest supports the tonearm when it is not being
used. Set the tonearm on its rest when it is not playing re-
cords. Clamp it into position if you don't have any im-
mediate plans to play records.
OO PLATTER/RUBBER PLATTER MAT
When the tonearm is moved and power is supplied to the
turntable, the platter will start rotating at the set rotation
speed. The rubber platter mat stabilizes the records and
also absorbs external vibration.
O DUST coVER
Keep this closed unless operating the controls or tonearm,
or changing over records. This serves to keep dust from
adhering to the records during record play. When fully
opened and pulled straight up, this dust cover can be re-
moved f rom the cabinet.
7

4. PL-3OO PANEL FACILITIES
BEFORE CONNECTING, CHECK THE
FOLLOWING:
a Switch the power to the amplif ier off to prevent damage
to the speaker system.
o The cartridge furnished with your turntable is an MM
type. Be sure to use a stereo amplifier which has PHONO
input jacks for this type of cartridge.
NOTE:
lf you are using a low-output moving coit (MC) carttidge, you will
need a special MC transformer or a head amptifier, or a stereo
amplifier with a built-in MC amplifier.
CONNECTION PROCEDURE
1. lnsert the phono cables (white and red) into the PHONO
input jacks of the stereo amplifier (white for left channel
into L jack, and red for right channel into R jack).
Platter/Rubber platter mat
Strobe lighr
O cur BUTToN
lf this button is depressed while the record is playing, the
tonearm automatically returns to the arm rest, and the
power to the turntable is cut off .
@ SPCCO SELECTOR BUTTON
45 . . . . . . When this button is depressed, the platter
will rotate at 45rpm. Depress for playing 45
rpm records, singles or EP's.
33 . . . . . . When this button is set to the released posi-
tion, the platter will rotate at 33-1/3rpm.
Release for playing 33-1/3rpm records like
LP's.
2.
3.
Connect the ground lead with the Y-shaped connector
at the end to the ground terminal.
lnsert the power plug into the convenience AC outlet of
the amplifier or a wall outlet.
STEREO AMPLIFIER
Phono input jacks AC outlet
Power cord
Dust cover
Anti-skate knob
Arm rest
@ nnu-elEVATtoN LEVER
UP ( ! ): When this lever is set to this position, the
tonearm will rise. Set it to UP before record
play and when you want to stop record play
while a track is being played or when you
want to change over to a different track.
DOWN ( I ): When the lever is set to this position, the
tonearm will be lowered. lf it is set to
DOWN for record play. the tonearm will be
lowered onto the surface of the record, and
play will begin.

5. DISASSEMBLY
5.1 PANEL AND BASE PLATE
1. Undo tlne 4 screws O securing the insulator
legs.
2. Move the tonearm across to the center, and
raise the panel a little.
3. Disconnect the D.D. motor and circuit board
connectors (2-pin and 5-pin).
}'. Size se lector
Motor Ass'y
F loat spring
(red)
Power
ass'v
G,-.\
,) P
t'1
rupply ]
2-pin
connector
./l
a/ s-pin colnnecto,.
Float spring (red)-@
\
g
U
-p
6
JK
\7
q
o
@
,JK
t--,
CI
o
g
@- Float spring
& (red)
{
o
I
Fiq.5-1

5.2 D.D. MoroR AND ToNEARM
1. After removing the panel, undo the 3 screws
O securing the motor.
2. Undo the 4 screws O securing the arm base.
DD motor ass'y
Fis.5-2
4.,.t'el
'-C;)
Tonearm ass'y

6. PANEL AND BASE PLATE ASSEMBLY
6.1 PL-200, PL-300
1. Rotate the motor clockwise by hand to reset
Lhe motor mechanism.
2. Move the tonearm across to the center (after
removing the main weight and headshell).
3. With the base plate half covered by the panel,
connect the microswitch 2-pin connector to
the power supply ass'y, and connect the power
supply ass'y ?-pin connector to the motor
ass'y. (See Fig. 1). Clamp all lead wires with
cord clamps, and check that there are no other
obstacles to normal operation of the mechanical
parts.
4. Shift springs A and B across to the left as shown
in Fig. 3, spring A being positioned to the left
of spring B. (When the cut button is pressed,
spring A will snap back to the right hand side
of spring B).
5. Then cover the base plate completely by the
panel, move the tonearm across to the arm rest
and clamp it into position.
6. Screw in the insulators (insulator case, float
spring, and damper rubber) to secure the panel
to the base plate.
* The front left hand float spring differs from
the other 3. Check that they are all correctly
mounted as shown in Fig. 1.
Fig. 6-1
Spring A
11

6.2 PL-255, PL-400
1. Rotate the motor clockwise by hand, and check
that the main mechanism has been reset to the
stationary state.
2. Shift the tonearm across towards the center,
and remove the main weight and headshell.
3. Attach spring A to the panel rib.
4. Set the size selector to the 30cm position, and
attach spring B to the panel boss.
5. Connect the 2-p connector from the micro-
switch to the power supply assembly, and the
7-p connector from the power supply assembly
to the motor assembly.
Note that all lead wires should be carefully
clamped into position at this time in order to
avoid loose wires being damaged by mechanical
operation.
6. Lay the panel on the under-base, and return the
tonearm to the arm rest and clamp it into
position.
7. Attach the insulators (case, float spring*,
damper rubber), and secure the panel to the
under-base.
*Note that the front left hand corner float
spring differs from the other 3. Refer to
Fig. 5-1 for correct mounting procedures.
8. Switch the size selector to the 25cm position,
and release the arm lock.
9. Rotate the motor clockwise while pressing down
on the center of the arm base, and check that
the main mechanism has been rest to the sta-
tionary state. During this operation, spring B
and lever A will engage each other as shown
in Fig.6-3.
10. When the start button is then pressed, spring A
will be released from the rib to engage the pin
on lever D.
This then completes the assembly of the panel
and base plate.
Spring B
Fis. 6 2
Fis.6-3
Spring A
Level A
Slider
Spring A

1
7. CIRCUIT DESCRIPTIONS
7.1 BLOCK DTAGRAM (pL-300, pL-400)
P42004
+
\\(
3nq
I a ["
ti
PD100s
vcc
PA2005 STO ROBE
vcc
13

7.2 .MOTOR OPERATION
1 Motor Construction
1. These motors are flat type 8-pole 6-coil slotless
Hall motors.
2. Besides the 3-phase Y-connected windings,
each motor is equipped with 3 phase-detector
Hall elements positioned at intervals 60' apart.
3. These Hall elements generate Hall voltages
which vary in level according to strength and
direction of magnetic flux changes induced
by the rotating rotor.
4. An independent FG magnet used to detect
speed changes has been positioned on the
outside of the rotor magnet. This FG magnet
has been designed with 200 magnetic poles,
and rotates opposite a printed coil mounted
on part of the circuit board. As the magnet
rotates an AC current signal is generated and
is used for speed detection purposes.
5. As can be seen in Fig. ?-1,the rotor magnet
generates an 8 polar trapezoidal magnetic wave,
and by phase additions of the coil switching
waveforms a even torque is obtained.
2. Principle of Motor Rotation
1. Assume that the rotor has stopped at the po-
sition as shown in Fig. 7-2.
2.In this position, Hall element HA is located
half way between an S pole and N pole on the
rotor, while HB and HC are opposite an N pole
and S pole respectively.
3. If the power is then turned on, the Hall element
outputs will be as indicated in Fig. 7-8.
4. The Hall element outputs are applied to the
position signal forming circuit (PA200bA),
resulting in the switching of the current flow-
ing through the drive coils.
5. These Hall element outputs are generated by
the rotational action of the rotor as shown
in Fig. 7-9.
6. These signals are thus used in switching the
drive circuit (also in PA2005A) to change the
direction of current flow in the coils, and
thereby determine whether an N or S pole is
generated, or whether the coil is switched off.
ln actual rotation, this happens as follows.
7. As the robor side of coil Lo becomes a south
pole, that of Lu becomes north, and L., neutral.
8. Repulsion between the S pole at La and the
rotor S pole, and attraction between the Ls N
pole and the rotor S pole exert a propulsive
force on the rotor.
9. As the rotor tums through 15" of arc, the
output from the Hall elements changes.
10. Ls now enters OFF state, Lc becomes a N
pole, and Lo a S pole.
11. The L6 N pole now attracts the rotor S pole,
and the La S pole attracts the rotor N pole.
Rotation continues.
12. Correspondences between rotor positions and
coil polarities are shown in Fig. 7-3, a-f..
a
HB
Fis. 7 -1
Fig.7 -2

a
HB
@
Hs Fig.7-3-a
Fis. 7-3-b
Fig. 7-3.e
Fis. 7-3-f
a
Hs
a
He
3. Speed Detection Section
1. The speed detection plate has one rows of
"detection patterns. "
2. The bottom surface of the rotor is magnetized
with 200 magnetic poles, and these rotate at a
short distance above the speed detection plate.
3. The output voltage from the detection patterns
has a frequency of 55.5H2 at 33-1/3 rpm, and
of. 7 \Hz at 45 rpm.
4. The signal is supplied to IC PA2004.
zt
Hg Fig. 7-3-c
z2
HB Fig. 7-3-d

7.3 OPERATION OF THE PDlOO3 IC
(OSCILLATOR STAGE)
1. Once the power supply is turned on, the quartz
crystal oscillator generates a 6744kHz signal.
2. The frequency of this signal is reduced to
1.5kHz (714096 division) by frequency divider I.
Part of the resultant signal is passed via the
x'tali RC switching circuit and applied to
frequency divider II. The other part of the
signal is applied to frequency divider selector II.
3. The 1.5kHz signai applied to frequency divider
II is further divided into a 750H2 signal, and
applied to frequency divider selector I where
the signals are converted into sampling pulses
for phase comparison purposes in PA2004.
33rpm 27.78H2
45rpm 37.5H2
(In both cases, the pulse width is 0.66?ms).
4. Frequency divider selector II converts signals
from frequency divider I into pulse signals for
the stroboscope lamp drive circuit.
33rpm 55.5H2
45rpm 71.OHz
(In both cases, the pulse width is again 0.667ms).
NOTE:
This IC (PD1003) is not employed in the motor of the
PL-200 and PL-225 models.
7.4 OPERATION OF THE PA2OO4 IC
(coMPARATOR CONTROL)
1. Signals from the frequency generator in the
motor rotation ass'y are changed into 50% duty
square wave signals by the waveform rectifier.
The frequencies at this stage are thus,
33rpm 55.55H2
45rpm 75Hz
2. Part of the output is divided by Vz in the FF
circuit, and subsequently applied to the FV
converter circuit along with the other part of
the output formed in step 1 above, thereby
forming the FV converter gate pulse sigaals.
3. The output from the FV converter is applied to
buffer amplifiers I and II.
4. The buffer amplifier I output is compared with
the reference voltage in buffer amplifier III, and
then applied to the output compose circuit.
5. Phase comparison of the sampling pulses from
the PD1003 IC with the FV converter output
occurs in buffer amplifier II, with the resultant
output being applied to buffer amplifier IV.
6. The output from buffer amplifier IV is also
applied to the output compose circuit.
7. This output compose circuit consists of a low-
pass filter (cut-off frequency 23H2, cut-off slope
-6dB/oct.) which serves to eliminate the carrier
component in the output of buffer amplifier II
(phase comparison).
8. This final output signal is then passed onto the
comparator control stage of the PA2005 IC for
comparison with the reference voltage.

7.5 OPERATION OF THE PA2OOs IC
(DRIVE CONTROL)
. Stroboscope Pulse Circuit
1. The platter has only a single row of stroboscopic
markings. Switchover for 45 and 33 rpm is ef-
fected by changing the frequency of the pulse
to the stroboscopic lamp.
2. From the Frequency Divider Selector I, a fre-
quency of either 7\Hz (for 45 rpm, representing
1/80 of 6000H2) or 55.5H2 (for 33 rpm, repre-
senting 1/108) is obtained and supplied to the
transistor that drives the stroboscopic lamp.
o Reverse Rotation Prevention
1. This motor operates indiscriminately in regard
to the direction of rotation. If the platter is
turned slowly in the reverse direction by hand, a
forward torque will be applied until the platter
stops, reverses its rotation and reaches rated
speed in the proper direction.
2. If, however, the rotational speed in the reverse
direction is in excess of 33 or 45 rpm, the
Forward/Reverse Command Block may "mis-
read" this as simply excessive speed ("overrun")
and apply a reverse torque until rated speed is
attained.
3. This reverse torque will further accelerate the
turntable rotation in the reverse direction. This
is.known as "reverse run-away."
4. To prevent this from happening, a Reverse
Rotation Prevention circuit has been included.
5. This Reverse Rotation Prevention circuit con-
sists of two flip-flops and AND gates See Fig. 7-4.
6. The input for this circuit is derived from the
Hall element position detection signals processed
in the Reverse Rotation Prevention circuit.
7. As long as the platter is rotating in the proper
direction, this pulse enters in the order B - A -
C, and no "reverse" command is generated.
8. If, however, the platter rotates in the reverse
direction, the pulse order becomes A - B - C,
and a corrective command is given to the For-
ward/Reverse Command Circuit.
FFr AND FFz
Sa
n
R
SO
R
L--) t r-Forced Forward
Rotation at 0 ou
Truth table
o Comparator Control and Forward/Reverse Com-
mand Circuit
1. Two inputs are supplied to the Control Com-
parator: a) a 4V reference voltage from the volt-
age stabilizer; and b) the output from the active
filters, which serves as the detection signal.
2. If the turntable rotates faster than rated speed,
the detection signal is higher than the 4V
reference.
3. When this happens, the Comparator Control
sends a command to the Forward/Reverse Com-
mand Circuit, telling it to apply a reverse torque
to the motor to slow it down.
4. Conversely, if ^turntable rotation is below rated
speed, the detection signal voltage will be below
the 4V reference.
5. In this case, the Comparator Control indicates
to the Forward/Reverse Command Circuit that
forward torque must be applied to the motor to
aicelerate it.
Operating point at zero load
+
lnput voltage differential between
0
pin
pin
AV18...Voltageat
V19...Voltageat pins (18) and (19)
Fis.7-5
(18)
(19)
Output
rtput
Fig. 7 -4
F F-r (AN I) FF:
STi () at l)rrt 2oul (J
F] o1o1ooo
A1o1oooo
I
cl o oIo11o1
AIo1oooo
.I
uoIoIo o o
.I
Co o o I I o1o
Area of 5
17

o Drive Circuit
1. The signals employed in the switching of Q2 -
Q7 in Fig. 7-6 are generated by 3 Hall elements,
and applied to terminals a, b, and c via the
position signal formation circuit.
2. "lhe phase of these step waveform signals is
displaced by 120' from each other.
3. When the step waveform signals at position I
in Fig. 7-7a are applied to the drive circuit
terminals a, b, and c, the potential at terminal
a will be lowered, resulting in Q2 being turned
on. The potential at terminal b will be raised,
resulting in Q6 being turned oh, but the
potential at terminal c will remain at the
reference level voltage (the bias settings for
Q4 and Q7 have been designed to prevent
these 2 transistors from operating when a
reference level voltage is applied).
4. Vcc will thus be applied across the Q2 - coil
La - coil Le - (2) - Q6 route, thereby pro-
ducing an S polarity in La, and an N polarity
in Ls.
5. Once the magnetic field is generated, the rotor
will commence to rotate. After the rotor turns
through 15' , the signals at position II in Fig. 7-7b
will be applied to terminals a, b, and c, thereby
resulting in a change in the flow routes of the
drive currents. After the rotor turns through
another 15', the signals shown at position III
in Fig. 7-?-c will be applied, again resulting in
changes in flow routes of the drive currents.
For every 15' that the rotor turns through, the
flow routes for the drive currents will change
as shown in Figs. 7-7d, 7-7e, and 7-'7f, finally
returning to the routes shown in Fig. 7 -7 a again.
6. A control voltage generated by the forward/
reverse direction discriminator indicator circuit
is applied to the control input terminal, thereby
controlling the flow of current in the coils.
1A
Fis.7-6

o2 -=a
l\)
+Q3 rs -l+l
n. { d
] LA i
t: r1
tt
I ta
o---_l 1 'u,=/
01 lltsh
-+#
\-/
o
a-> ueJ O
IS L€ CH
ool €
Control
input a,l NN
Lz --R
.t
{ t- 03 -R l-
-fi\._)
o
a:> o{o
Os
.LH
86€
.\
Control
i nput J, ILJ
t-
GND
Fig.7 -7 -a
Fig.7-7-b
Fig.7 -7-c
Fig.7 -7 -d
Fig.7-7-e
02 --@,
l- Q3 -e
I \_->
tl f,4 1
-l
-----,-,=--1
Or ll
o,t ll
.^a
I
',F"^Fui"
{{ooo-.1 O
| .--
15ru ,:1-@
Control
input J' I L,/
I +
cNn
02 --@
I \.J
l- [ ,-.
Q3 r-ff
l-
o
f,rZ l o"-j O
l5 CH
06 t-C
Control
i nput Ql ILJ
GNI)
vcc
Qz -Rv1rffiJlt
r-4 I tr d6D
I7 Ir
-:-lA\
3 ll Kb.
t5,
e
tr|#A rboJ O
t | '/">
15 ru ail
06€
i',ft{
Control
input .1, I a,/
{ +
GND
VCC
82 l- 03rc r-ll
^l I \
t4 | LaB
l9 j
+l I
-lA'
3*ll',Hbi-
-tK
o
/-> bo-{ O
J5 L€ ,:l*Lc
Control
i nput f, Itl
Nt)
f-
br
C .--
Fig.7 -7 -t
19

45"
I
P
c
o)
E
q)
UJ
(U
Io
U'
E
o
q)
(u
=
f
o
f
o
Her
HA Hez
Hs X:;
Hcr
Hc Hcz
,' L4(H41+Hg2)
E
L
o
q)
(o
3
c)
'; LB(HB1+Hs2)
o
o-
E
o
oLc(HA2+Hc1)
C
o
(u
o
E,
E
(!
3
o
u-
c rH
o Al
F IH
(El
5 lH
G Bl H
o)l
u,
b IH
<u \H
EE
For'ward Rotation E + A .*.
Reverse Rotation A* B--*l
Fis. 7-8-b
Fis. 7-9