Section 6 — Circuit Description

(original pages 103-129)

6.1 Logic PWA

6.1.1 Brief Description

The logic board controls the following functions and indicators:
  1. Start, Stop, Fast Forward, and Splice Transport Functions and Lamps
  2. Record Set, 1 kHz Defeat, Record Lamp, 1 kHz Defeat Lamp
  3. Audio Switcher Control, Audio Lamp
  4. Flashing Ready Lamp
  5. Clock Reset & Clock Enable Control
  6. Motor Speed Control
  7. Solenoid Control
  8. Splice Finder Detector
  9. Record and Cue Tone Dias Enable
  10. Stop Sensor Mute

6.1.2 Detailed Description

IC U12 Type 4044 contains four R-S type flip flops. The flip flops and input/output pins are:
  1. Start (Set, Reset, Output) (3, 4, 13)
  2. Fast Forward (7, 6, 9)
  3. Splice (11, 12, 10)
  4. Record (15, 14, 1)

When the set input is momentarily pulled low the output will go high, pulling the reset low will cause the output to return to a low state. IC U10 type 74C42 BCD to decimal decoder allows only the first transport switch pushed (Start, Stop, Fast Forward or Splice) to reach U12. When a U10 input (15, 14, 13, 12) goes high its respective output (2, 3, 5, 10) will go low. U11 will decode the low commands and reset all U12 flip flops except the one being set by U10. The exception is resetting the Fast Forward flip flop U12-6 when going from fast forward to the Start mode. During this mode the reset signal comes from U9-10. U12 will not reset until the Servo Motor has slowed down to normal speed and the servo error indicator has extinguished.

ICs U13 and U14 invert and buffer U12 outputs. Transistors Q6-Q9 drive front panel and remote control lamps.

U7-9 goes high when the machine is in the Stop mode (U12 outputs 13, 9 and 10 are low). U8-3 is normally low and goes high when the machine is in Fast Forward. U8-3 will return to a low state when the machine is going from Fast Forward to Start (U12-13 and U12-9 both high). U8-4 will go high, sending the motor a Fast Forward command if the machine is in the Splice mode (U12-10 high), or if U8-3 is high.

U7-10 goes low to mute the Secondary and Tertiary tone sensors when the machine is not in the Start mode. U2-10 goes low when the machine is in the stop mode and will remain low for 2 seconds (as determined by R40 and C17) after the machine leaves the Stop mode inhibiting the operation of the 1 kHz stop sensor. In addition, U2-10 goes low for 2 seconds when additional stop tones are recorded.

U18-9 goes high to enable the Program Record Bias when the machine is in the Start (U12-13 high) and Record (U12-1 high) mode and delay gate U17-3 is high. U17-3 delays the Bias Enable Signal while the solenoid is energizing.

U18-10 goes high to enable the Q tone record circuitry when the machine is in the Start and FAST FORWARD (U12-9 low) mode and delay gate U17-3 is high.

When U14-12 is high (from pushing the record switch) and U4-10 is high (machine in Stop/Ready mode) and U5-13 is high (Stop Switch not pushed), U5-10 will go low. This will result in U15-10 (4528 mono stable) momentarily going low and setting the record flip flop (U12-15). When the Record mode is set (U12-1 high), U16-4 (4013 D-Flip Flop) is low enabling a second pulse from U15-10 (if the record switch is pushed again) to set U16-1 high and defeat the automatic 1 kHz Q tone record circuit.

U3 type 4044 contains four R-S type flip flops. The four flip flops and their input/output pins are:

  1. Slow Flash (Set, Reset, Output) (3, 4, 13)
  2. Fast Flash (7, 6, 9)
  3. Timer Control (15, 14, 1)
  4. Audio Switcher (11, 12, 10)

When the set input is pulled momentarily low the output goes high. When the reset input is momentarily pulled low the output will return to a low state.

When the machine leaves the stop mode U7-9 goes low and U4-11 after a short delay also goes low. A pulse to U3-7 and U3-3 sets both the slow and fast flash flip flops (U3-9 and U3-13 both high). The main AC to the machine is divided to the frequencies denoted as slow and fast. These are connected to U8-12 and U8-8. When the machine is stopped by pushing the stop switch U4-3 goes low and resets the small Fast Flash flip flop. When the machine stops on a splice or a stop tone U4-4 resets the slow flash flip flop. U8 passes the proper flash signal to U7-3 or U7-4. U7-5 is high with the machine in the STOP/Ready mode enabling the flash signals to reach Q11 and flash the stop lamp. In addition, signals from U3-9 and/or U3-13 may be jumped to inhibit the start switch after the tape has been put in motion. Removing the cartridge pulls edge connector pin 25 low which results in U4-3 and U4-4 going low resetting both flash flip flops. In addition, removing the cartridge results in U4-10 going low turning off the STOP/Ready lamp and U5-6 going low resetting all U12 flip flops, U16, and disabling all transport switches. Re-inserting the cartridge will turn on the Stop/Ready lamp and enable the transport switches.

When the START Switch is enabled U3-11 will go low for the duration the switch is held. Audio switcher flip flop output U3-10 will go high turning on Q3 and the AUDIO Lamp. Transistors Q2 and Q1 create a short pulse which resets the Audio Switcher flip flop. This pulse is shorter than the time the START switch is held so the Audio Switcher remains in the set mode. Connecting the Audio Switcher interlocks of several machines together will result in all Audio Switcher flip flops being reset except the Audio Switcher of the last machine started. When the Audio Switcher on U17-4 is low, U17-3 is high and U2-11 is high which turns on the Audio Gates on the PLAY AMP PWA. The Audio Switcher is reset when the machine leaves the START mode and U14-4 goes low. When the machine is in the FAST FORWARD mode holding the Fast Forward switch will result in U2-11 going high to unmute the Audio.

U1-1 U1-5 goes low when the machine leaves the stop mode. U1-4 U1-7 outputs a pulse to U3-15 setting the timer flip-flop output U3-1 high enabling the front panel timer count. Pressing the STOP Switch will freeze the timer. When a cartridge is inserted U1-10 U1-12 will go high resulting in an output pulse from U1-13 U1-9 which will reset the timer. Additional pulses from U1-13 U1-9 will reset the timer when the machine leaves the Stop mode, unless the 1 kHz DEFEAT indicator is on (U17-13 low). U18-6 buffers the reset signals and resets the timer.

Jumpers may be installed to initiate FAST FORWARD, freeze the clock, or turn off the Audio Switcher when the Secondary cue is present. U13-12 goes low at the beginning of the Secondary tone and U15-7 goes low at the end of the Secondary tone to perform the desired function.

U20 and U19 control the transport solenoid. In the STOP mode, U20-3 is connected to U20-4 and C20 is charged to +15 V. U20-2 is grounded through U20-1. U20-10 is open and pulled low by R37. When the machine is started U20-10 connects to U20-11 and +15V is routed to U19-5 and the solenoid energizes and draws full current. At the same time U20-3 and U20-4 open and C20 discharges to a lower voltage determined by R44 and R37. As the voltage to U19-5 drops so does the solenoid current. R35 monitors the solenoid current and adjusts the output U19-7 to maintain constant solenoid current.

When the machine is placed into the SPLICE mode the sequence is identical except U20-1 is open From U20-2 allowing U19-3 to be biased at 1.2V. When C20 discharges below 1.2V, U19-1 (which is normally low) goes high and connects a lower voltage ([HYPERLINK]see mother board schematic) to the solenoid. This lower voltage results in a lower current which is sensed by R35 and drives U19-7 high disabling the constant current function. U21 forms the splice detector circuit. C24 is connected to the solenoid and U21 amplifies any EMF pulses generated by plunger motion when a splice passes between the capstan and pressure roller. U17-10 goes low and U2-4 goes low stopping the machine. D25 inhibits the splice detector while the motor is accelerating. D8 inhibits the splice detector in all other modes of operation.

1 kHz cue stop signals are input to U9-6. They are inhibited for 2 seconds after starting and while in the splice mode by U9-5. When enabled (U9-5 high) and with a 1 kHz STOP tone (U9-6 high), U9-4 and U2-4 will go low stopping the machine.

6.2 Tone Sensor PWA

6.2.1 Brief Description

The TONE SENSOR BOARD provides the following functions:
  1. Crystal oscillator and clock signals for motor speed, cue tone sensor frequency, cue tone generator frequency and bias oscillator
  2. Cue tone head preamplifier and booster amplifier
  3. Cue tone filters, detectors, relays
  4. Motor speed control

6.2.2 Detailed Description

Crystal X1 and associated inverters generate an 18.432 MHz clock signal. U4 and U5 divide the clock to 144 kHz, 288 kHz and 18 kHz. The 144 kHz signal is routed to the RECORD PWA where it is filtered to a sine wave and used for record bias. The 288 kHz signal is further divided on the TONE GENERATOR PWA to provide 1 kHz and 8 kHz cue tone record generators. In addition, the 288 kHz signal is divided to the 9600 Hz motor reference frequency by U24 and U23. The 18 kHz signal is divided to 300 Hz; 900 Hz and 1800 Hz providing auxiliary motor speed references.

The D.C. Servo Motor system requires a reference frequency proportional to the motor speed. When operating at 3.75 i.p.s. the reference frequency is 300 Hz and doubles as the speed doubles (600 Hz at 7.5 i.p.s., 1200 Hz at 15 i.p.s.). U14-3 outputs the proper reference frequency to the servo motor system from signals supplied by U13, U7 and U8.

U14-3 Motor Reference Signals
Speed 3.75 i.p.s. 11.25 i.p.s.
Frequency 300 Hz 900 Hz
Speed 7.5 i.p.s. 22.5 i.p.s.
Frequency 600 Hz 1800 Hz
Speed 15 i.p.s. 30 i.p.s.
Frequency 1200 Hz 2400 Hz

Jumpers W1 - W3 are used for selecting 3.75, 7.5 or 15 i.p.s. operation.

The motor tachometer signal is input on card edge pin 26. When the motor is operating on speed (no SERVO ERROR lamp), the signal frequency at pin 26 will be equal to the frequency at U14-3. U20 divides the motor tachometer and U21-3 outputs a signal normalized to 300 Hz.

U21-3 Normalized Signal
Speed 3.75 i.p.s. 11.25 i.p.s.
Frequency 300 Hz 900 Hz
Speed 7.5 i.p.s. 22.5 i.p.s.
Frequency 300 Hz 900 Hz
Speed 15 i.p.s. 30 i.p.s.
Frequency 300 Hz 600 Hz

U25 divides the normalized signal by 300. A 1 Hz signal is output at U16-1 U16-11 and is level shifted at U102. This signal is used by the front panel timer. As the motor accelerates or decelerates the 1 Hz signal will change frequency proportional to the motor speed and the timer will always show true tape time.

The normalized signal also is routed to U12 and U18 which multiply the normalized signal by 1330, producing an output signal at U12-4 of 399 kHz for a 300 Hz input. U11 divides the 399kHz to 49.875 kHz and 12.469 kHz. After level shifting by U10 these signals are routed to U1 and U2 type MF10 switched capacitive filters, which are utilized in the cue tone detection system. They are configured as Bandpass filters with center frequency determined by the clock signal input to pins 10 and 11. The center filter frequency is determined by and is proportional to the motor speed.

U27 is the cue head preamplifier and booster amplifier. Boosted cue signals are routed to U1 and U2 through level sensitivity trimmers. U9 rectifies and detects the output signal from U1 and U2. U17 inhibits U9 Secondary and Tertiary output signals when the machine is in FAST FORWARD.

U26 amplifies an external motor speed reference. When the VARY SPEED Enable (edge connector pin E) is pulled low the external speed reference will be substituted for the internal 9600 Hz reference. When the machine is in the RECORD mode the VARY SPEED Enable is defeated.


6.3.1 Brief Description

The PLAY AMPLIFIER provides the following functions:
  1. Left and right channel amplification and equalization
  2. Mono, Stereo and Matrix Audio switching
  3. Audio Mute
  4. CARTSCAN logic, inversion switches and lamp drivers

6.3.2 Detailed Description

U7 receives CARTSCAN information from the optical sensors on the deck. CARTSCAN Inversion Switch S1 allows these signals to be inverted or remain in their normal state. U6 enables the CARTSCAN system only when a cartridge is ready. D1, D2 and two sections of U8 prevent MONO and MATRIX from operating jointly. Q5-Q8 drive the front panel CARTSCAN indicators.

The left channel play head is connected to (1/2) U4 and A2 which provides 20 dB of gain. Head loading and gap loss correction is provided by R110, R111 and C43. The second half of U4 provides amplification and equalization. R82 adjusts low frequency equalization and R96 adjusts high frequency equalization.

The right channel signal path is identical to the left with the exception of R100 which is used to balance the level at U3-10 (the right output) with the level at U4-10 (the left output).

U10 decodes the sum (L+R) and outputs discrete left at U10-1, and decodes the difference (L-R) and outputs discrete right at U10-7 when operated in MATRIX mode.

U9 connects the audio from the left and right equalized preamplifiers or from the MATRIX decoders to the output amplifiers. U9 receives MONO and MATRIX logic signals from the CARTSCAN logic. In addition, U9 functions as the audio gate providing 70 dB of muting when the audio gate is off. The audio gate control signal from the LOGIC PWA is input to card edge connector pin U.

U1 provides output amplification and signal inversion for the left channel balanced output. R21 or R17 sets the output level, depending on whether Q1 or Q3 is turned on by the Normal/Elevated CARTSCAN logic.

U5 provides the same function as U1 for the right channel.


6.4.1 Brief Description

The TONE GENERATOR provides the following functions:
  1. 12 Frequency Test Tone Oscillator
  2. Meter Function Switch
  3. Meter Amplifiers
  4. Meter Control Logic
  5. 1 kHz Cue Tone Generator
  6. 150 Hz Cue Tone Generator
  7. 8 kHz Cue Tone Generator
  8. 1 kHz Cue Tone Record Timer
  9. Program and Cue Bias Control Logic

6.4.2 Detailed Description

IC UB type 2206 is a function generator configured as a 12 frequency sine wave oscillator. The oscillator frequency is determined by the position of S5. Trimmers R49 and R50 are distortion null controls. Trimmer R13 adjusts the oscillator output level. Three position switch S4 is used to

[This section of the initial version of the manual is too scrambled to resurrect correctly. Other than eliminating some duplication, it is presented here verbatim.]

disconnecph card edge pin 4) when S4 is in the “0” or “−10” position.

Signals to be metered on the left VU meter are routed to U3, a 4051 analog switch which selects one of the five signals present and outputs the selected signal to 1/2 U5 for buffering. The signal is full wave rectified by the second half of U5 and 1/2 U7 and then routed to the front panel LED VU meter drive circuit. U3 utilizes information from Meter Select switches S1, S2, and S3, in addition to the associated logic to select the proper signal to be displayed.

Right channel metering is similar and will not be discussed.

A 288 kHz signal supplied from the TONE SENSOR board is divided to 24 kHz by U17 and U18 and routed to U19-6. When the Tertiary (8 kHz) cue tone record switch is pushed and if the cue record/cue bias enable (card edge pin 18) is high, the 24 kHz signal will be gated to U12-1. The signal will then be divided to 8 kHz by U13. The 8 kHz and 24 kHz signals are actively summed and then filtered by U14 to produce an 8 kHz sine wave.

A 3 kHz signal is supplied from U18-5 to U19-12. When U19-13 is pulled high the 3 kHz signal will be gated to U12-13. The signal will then be divided to 1 kHz by U20. The 1 kHz and 3 kHz signals are actively summed and then filtered by U21 to produce a 1 kHz sine wave.

A 450 Hz signal is supplied from the TONE SENSOR PWA to U19-2. When the Secondary cue tone record switch is pushed and if the cue record/cue bias enable (card edge pin 18) is high, the 450 Hz signal will be gated to U125. The signal will then be divided to 150 Hz by U15. The 150 Hz and 450 Hz signals are actively summed and then filtered by U22 to produce a 150 Hz sine wave.

The three filtered cue tone signals are summed together and sent to the RECORD AMPLIFIER PWA through card edge pin 14.

Secondary and Tertiary cue tone record duration is controlled by the length of time the tone record switches are held. The primary cue tone record duration is controlled by U11 type 4528 dual monostable. IC U9-9 is normally high and goes low when the automatic 1 kHz cue tone record function is defeated.

U11-9 will go low for 1/2 second to record a primary cue tone when the machine first enters the RECORD and START mode if U9-9 is high.

When the tape is running in the START mode, pressing the RECORD switch will result in U11-7 going low for 1/2 second and recording an additional stop tone. The 1 kHz stop tone sensor is muted when additional stop tones are added so that the machine will not stop.

IC U10-13 will go low to turn on the bias oscillator when the machine is in the RECORD and START mode. In addition, U10-13 will go low when the machine is in the START mode and cue tones are being recorded.


6.5.1 Brief Description

The RECORD AMPLIFIER performs the following functions:
  1. Left and Right balanced input amplifiers.
  2. MATRIX, MONO and ELEVATED LEVEL program audio processing.
  3. Program record equalization.
  4. Program group delay compensation.
  5. Left, Right and Cue Head drivers.
  6. Bias oscillator filter.

6.5.2 Detailed Description

ICs U14 and U13 filter the 144 kHz bias signal from the TONE SENSOR board. Diodes D21, D22 and D17 control Q4 which ramps the bias signal on and off.

ICs U1 and 1/2 U9 form a differentially balanced instrumentation amplifier for the left channel record input. The signal is routed to the front panel RECORD LEVEL control.

The level adjusted signal is then routed to U11, a 4066 Quad Analog Gate. U11 is configured as a bipolar switch and will select for recording either the signal from the front panel level control or the output of the 12-tone test oscillator located on the TONE GENERATOR PWA. The selected signal is buffered by the second half of U9.

The right channel signal path is identical to the left with the exception of R95 which is used to balance the level at U10-7 with the level at U9-7.

IC U12 is used to generate the L+R (U12-1) and L-R (U12-7) signals required for MONO and MATRIX stereo recording.

IC U3 type 4052 dual 4 channel analog switch receives CARTSCAN logic information from the PLAY AMP PWA and selects discrete stereo, MATRIX stereo or MONO and routes the proper signal(s) to U4 for buffering.

IC U7 type 4053 triple 2 channel analog switch receives CARTSCAN logic information and selects normal or elevated level, equalization and bias controls for the left channel.

IC U6 provides left channel record high frequency equalization by summing the output of U6-7 (high pass filter) with the left channel signal at U6-2. The amount of high frequency boost is controlled by R9 or R11 as selected by U7. Capacitor C29 is normally supplied shorted out by JM1. With JM1 removed the equalizer will introduce a 3 dB boost at 50 Hz in accordance with the 1964 NAB Equalization Standard. Left channel group delay compensation is provided by 1/2 U8 and is adjusted by R46. The output from the group delay amplifier U8-12 is summed with the 144 kHz bias signal and is then routed to the second half of U8 which drives the left channel record head. The amount of record bias is adjusted by R13 or R14 as selected by U7.

The record head driver insures constant current operation by placing the record head within the feedback loop. Record head current is sampled across R104 and is fed back to U8-7.

ICs U15, 16 and 17 perform the same function for the right channel.

IC U5 is the cue track summing and record head drive amplifier. The three cue tones from the TONE GENERATOR PWA are routed to U5-1. Trimmer R6 controls the record level of the three cue tones. Trimmer R7 adjusts the cue record bias and trimmer R8 adjusts the record level of external logging information. FET Q1 conducts when the cue track is recording, summing the bias with the signal to be recorded. The cue record head driver is similar to the program record head driver described previously.


6.6.1 Brief Description

The SERVO PWA performs the following functions:
  1. Motor Speed/Torque Control
  2. Motor Braking
  3. SERVO ERROR Indicator

6.6.2 Detailed Description

IC U2 is a 74LS123 dual mono stable. A motor reference signal from the TONE SENSOR PWA (See [HYPERLINK]Section 6.2.2 for Frequency Information) is routed to J2-5. The reference signal is buffered by U9 and input to U2-10. For each positive going transition of the reference signal U2 will output a constant duration negative going pulse at U2-12.

The motor has a built in 80 pole tachometer whose analog signal is amplified and squared by U4 and then routed to U2-2 (after buffering by U9). U2 will output a constant duration negative going pulse at U2-4 for each positive transition of the tachometer signal.

ICs U1 and U5 form a left/right shift register whose output duty cycle at U5-4 is equal to the phase/frequency difference between the reference signal and the motor tachometer.

When the motor is accelerating, U5 pins 4, 14, 5, 13, 11 and 15 will be high. With U5-4 holding U3-11 high, the motor overspeed detector will be held in the reset mode.

The brake control output U7-1 will also be held in low mode by holding U7-4 high. In addition, when accelerating U5-15 is high, U7-11 will be pulled high setting U7-13 high and turning on the SERVO ERROR indicator.

When the motor has achieved proper speed (motor tachometer frequency is equal to the motor reference frequency) U5-15 will go low and a square wave will appear at U5-4. The frequency of the square wave will be equal to the motor reference frequency and the duty cycle will vary according to the motor load. The greater the load, the more positive the duty cycle.

The output from U5-4 is filtered to remove the carrier signal (reference frequency) from the control signal (duty cycle variations). The filtering is performed by R11, R12, R14, C15, C16, C19 and 1/2 of U8). Resistor R13 and capacitor C17 form a lead network that helps compensate for the motor’s mechanical time delay and allows higher system gain. Components R29-R36, 1/2 of U8, and Q2-Q4 form the motor drive amplifier. Motor current is sampled across R36 and fed back to U8, U1A and R25 R35, the system gain control.

The motor contains three drive coils in a Y configuration which are sequentially turned on and off as the motor rotates producing a three phase drive system. Three Hall effect sensors placed 120 degrees apart monitor the motor’s position and select the proper drive coil. When the motor is accelerating or operating at the proper speed, U6 type 4053 analog switch connects the output of the Hall sensors to Q6, Q8 and Q10 which control the coil switching transistors Q5, Q7, Q9. The common point of the three coils is connected to the output of the motor drive amplifier at J1-12. The motor drive amplifier controls the current flowing in the three drive coils.

When the motor load is increased the duty cycle at U5-4 goes more positive resulting in the filter output at U8-1 going more positive which turns Q2 on harder and increases the current in the three drive coils. The motor only consumes the amount of power needed to properly drive the load.

When the motor is decelerating, U5 pins 4, 14, 5, 13 and 15 are low. The motor drive amplifier is turned off and no current flows in the drive coils. During this time, U5-11 outputs pulses to the overspeed detector input U3-10. When U3 type 4040 has counted a sufficient number of pulses indicating that braking is required, U3-2 goes high setting U7-1 high. This results in U6 disconnecting the sensors and replacing them with a high signal to Q6, Q8 and Q10 which turns on all three drive coils. With the motor drive amplifier off, the three drive coils become three voltage generators whose parallel connection results in effectively short circuiting the drive coils thus slowing down the motor. IC U7-13, has also been set high by the low output at U5-5 which illuminates the SERVO ERROR indicator.

When the motor returns to the proper speed, the output at U5-4 returns to a square wave. This signal turns off the SERVO ERROR indicator and reconnects the Hall effect sensors to Q6, Q8 and Q10.

Diodes CR2 and CR3 rectify the tachometer signal and components R2, R5 and 1/2 U4 form a comparator. If the motor is stalled (no tachometer) U4-7 will go low limiting the maximum current of the motor drive amplifier.

The motor tachometer is output at J2-6. This signal is used on the TONE SENSOR PWA to generate cue tone sensor frequencies and to generate the 1 Hz signal displayed by the front panel timer.


6.7.1 Brief Description

The FRONT PANEL LAMP PWA performs the following functions:
  1. Timer display and control (RECORDERS ONLY)
  2. VU meter display (RECORDERS ONLY)
  3. Machine status indicators
  4. CARTSCAN indicators

The timer display and control circuit, and the meter display circuit are the only active circuitry present on the FRONT PANEL LAMP PWA.

6.7.2 Detailed Description

The front panel mounted digital tape counter consists of a 4-digit seven segment multiplex type display and a 7217 IC (U1) counter. IC U1 is configured as an up time counter with a maximum display of 59:59, and is capable of directly driving multiplex seven segment displays. Pulses from the motor tachometer amplifier are normalized and divided on the TONE SENSOR PWA and then are routed to the counter input U1-8 which counts and displays the number of pulses. One pulse equals one second of real tape time. The LOGIC PWA will send a reset signal to U1-14 when a cartridge is inserted or the cartridge is started from the STOP/ready mode. No reset signal is generated when the automatic 1 kHz cue tone recording circuit is defeated.

The VU meters consist of a 10 segment (7 green, 3 red) LED bar graph and a LM3916 VU meter display driver. The signal to be metered is selected and rectified on the TONE GENERATOR PWA and is then routed to the LM3916 input. The LM3916 compares the input level with the full scale level and illuminates the proper LEDs.


6.8.1 Brief Description

The CARTSCAN PWA performs the following functions:
  1. Sensing of the four reflective CARTSCAN labels
  2. Optical cartridge ready switch
  3. Cleaning switch
The CARTSCAN PWA is mounted tc the right cartridge guide.

6.8.2 Detailed Description

Reflective sensors O1-O4 each contain an infra-red LED emitter and a phototransistor. When a reflective object is placed in front of the sensor the emitted infra-red signal is reflected back to the phototransistor and the transistor conducts. These reflective sensors detect the presence of the CARTSCAN reflective label and output a CARTSCAN logic signal to the PLAY AMP PWA.

A separate LED and phototransistor are configured as a light beam interrupter. When a cartridge is inserted the light beam is broken mechanically turning the phototransistor off. This High-with-Cartridge-Inserted signal is routed to the LOGIC PWA.

A conveniently located cleaning switch is connected in series with the High-with-Cartridge-Inserted signal. When the switch is placed in the open (up) position the machine indicates that it is ready to start without a cartridge in place.


6.9.1 Brief Description

The MOTHER PWA provides the following functions:
  1. Interconnection between PWAs.
  2. Power supply and voltage regulators.
  3. Solenoid drive circuitry.
  4. Ready lamp flash clock generator.

6.9.2 Detailed Description

The power transformer features dual primaries allowing the CTR100 to be configured for 120 or 240 volt operation. In addition, the transformer has two secondary windings.

The first secondary is utilized in a center tapped bipolar full wave configuration. Diodes D1-D4 rectify the AC and capacitors C1, C2 and C3 provide filtering. Three terminal regulators are utilized to provide the +15, -15, and +5 operating voltages.

The remaining secondary is rectified by Z1 in a full wave bridge configuration. Capacitor C6 provides filtering. This raw DC is used to operate the D.C. Servo Motor and the solenoid.

The raw D.C. is routed to the solenoid through Darlington transistor Q1 in all modes except splice find. Transistors Q2 and Q6 are configured as a Darlington pair and are used for solenoid current regulation. A current signal is sampled across R6 and fed back to the LOGIC PWA. Transistor Q7 momentarily connects the low side of the solenoid to the unregulated negative supply when the solenoid is first energized insuring fast pressure roller engagement. Transistors Q3 and Q2 provide level shifting between the solenoid drivers and the LOGIC PWA.

IC U1 and related components divide the AC primary frequency and supply fast and slow pulses to the LOGIC PWA. The pulses are utilized by the ready lamp flash circuit. Transistor Q5 is used to reset U1 and allows the ready lamps of several machines to be synchronized.