System 700

СТ-700$

Service Manual

Specifications

Contents

Instruction Information

Features Installation Tuner Connections

Tuner Power Supply Control Functions

Tuner Operation Trouble Shooting Guide

Circuit Description

PLL Frequency Synthesizer FM Front End & IF MPX Stereo Demodulation Signal Meter Scan Stop Operation Muting Operation AM Tuner Circuit

Service Information

Measurement Condition Test Equipment Operation & Standard Setting FM Alignment AM Alignment Block Diagram PC Board Layout Exploded View Replacement Parts List Schematic Diagram

Specifications

Power consumption. Power supply. Dimensions.

Width

Height

Depth

FM

Frequency range. Sensitivity.

50 dB quieting sensitivity. Mono

Stereo

Total harmonic distortion.

Mono

Stereo

S/N.

Mono

Stereo

Frequency response.

Alternate channel selectivity.

Capture ratio. | Image rejection ratio. IF rejection.

Spurious response rejection.

AM suppression. Separation. 1kHz

10 kHz

20 Watt. Carrier leak (19 kHz).

220V 50 Hz AC. Output voltage.

AM

Frequency range. Sensitivity. Selectivity. Image rejection. 87.5 to 108.0 MHz. S/N.

10.3 dBf (1.8 microvolt ІНЕ '58). Output voltage.

420 mm. 48 mm. 430 mm.

16.6 dBf (3.7 microvolt ІНЕ 58), 37.2 dBf (39.2 microvolt IHF 58).

0.1% 1 kHz. 0.2% 1 kHz.

75 dB.

70 dB.

30 to 15,000 Hz +0, —0.5 dB. 80 dB.

1.2 dB.

70 dB.

90 dB at 98 MHz.

85 dB at 98 MHz.

55 dB.

50 dB. 39 dB.

65 dB. 715 ту.

531 to 1,602 kHz. 300 microvolt/m. 45 dB.

50 dB at 1 kHz. 50 dB.

300 mV.

Instruction Information

Features

The Cybernet model СТ-700$ is a high fidelity stereo tuner designed to be incorporated with other System 700-series components the integrated stereo amplifier model CA-700 and the stereo cassette deck model CCD-700 into a complete stereo system. It features the following:

Fluorescent digital AM/FM frequency display/Automatic and manual tuning with digital PLL synthesizer/Memory pushbutton tuning for 7 AM and 7 FM stations/Short-time-hold [STH] feature for temporary station tuning/Switchable indicator array for signal strength or multipath interference indication/ Multiplex filter for reduction of residual multiplex pilot noise/ Sensitive dual gate MOSFET in the FM front end/High selectivity IF stage with 3 dual-element ceramic filters/ Phase-locked-loop [PLL] multiplex stage for stable stereo demodulation/IIluminated pushbuttons.

Tuner Connections

Installation

Installation of your new tuner is not complicated. However, the following guidances must be followed for satisfactory performance and easy operation of the system.

Do not remove the cover there are no user serviceable parts inside the unit. Refer servicing only to the qualified personnel/The unit must not be exposed to excessive dust, moisture, or direct sources of heat and sunlight/To clean the cover, wipe with soft cloth soaked in a neutral cleaner or a polishing cloth. Do not use benzine or thinner which will damage the cover finish.

AM Loopstick Antenna

Antenna Terminal (See below)

ЕМ 75 Ohm У Antenna

FM 300 Ohm Antenna

75 Ohm Coaxial Cable

ан = {ЕЧ ЖАА 1 Remove 30 mm of outer insulation 2 Remove all but 20 mm of the shield

braid 3 Remove innerinsulation leaving 10 mm of the insulation exposed.

Power Plug 220V 50 Hz

Tuner Output:

Use shielded audio cables. Connect to amplifier Tuner input terminals.

Clamp and secure

AM Longwire

300 Ohm Twin-Lead Cable

пене чне И

Remove 20 тт of insulation and 30 mm of bridge. Strand exposed conductors.

AM Antennas

Select use of attached loopstick or additional long-wire antenna for AM reception.

Ferrite loopstick antenna. The ferrite loopstick antenna is а sensitive pickup element of the AM tuner sections. For maximum station reception, it must be properly positioned away from the rear chassis and other metallic surfaces. The associated connecting cables and AC power cord should be dressed as far away as possible. For optimum performance, the antenna should be positioned for maximum signal strength indicator indication when the unit is tuned to the desired AM station.

External AM antenna. AM antenna terminals аге provided for a properly designed long wire AM antenna system. Such antennas are useful when the desired AM stations are at a considerable distance from the tuner. A simple long wire antenna can consist of a length of single conductor, insulated wire of 30 feet (9 meters) or longer, extending from the tuner external AM antenna terminal to the outside

of the building. This wire should be positioned away from electrical cables and appliances. Аза rule, the longer and higher the antenna, the better the reception. However, as signal pick up of broadcast station is increased, so also is the pickup of undesirable man-made interference. Therefore, the external AM antenna should be evaluated on a trial-and-error basis.

FM Antennas >

Select dipole supplied or connect suitable external antenna system.

Supplied 300 Ohm FM Antenna. An FM dipole antenna is supplied with your tuner. In strong signal area, this should be

antenna. The braided outer conductor is connected to ground clamp. Refer to connection diagram for

proper cable preparation and hook-up. This type of lead-in offers the same advantages as shielded 300 Ohm cable by minimizing interference picked up by the lead-in cable.

Grounding. Under certain conditions a good earth ground will improve performance of the tuner by reducing interference conducted via the power line. A good ground may also improve the AM performance. Good earth ground dictates that the ground wire be as short as possible, connected to a specifically designed, copper clad steel rod driven into moist earth, or to the cold water supply pipe as it enters the building. Clean oxide from rod or pipe and use suitable ground clamp.

Tuner Output. Use insulated and shielded audio cables terminated with standard pin [cinch] plug. Connect to the input jack on your amplifier or receiver. Observe proper channel connection.

more than adequate for reception of most FM stations. Antenna connections are made to the terminal strip marked FM-300 Ohm located on the rear panel. The dipole

leads are connected to the screws marked 300 Ohm. The ground screw is not used for the dipole antenna. The dipole should be unfolded to its full T-type size and oriented for optimum performance. Dipole antennas are most sensitive to FM reception when positioned perpendicular to the station. Exterior FM 300 Ohm Antennas. For fringe [weak signal] areas, or areas where interference to FM reception is high, the use

of a log-periodic, or Yagi-type antenna system is

recommended. These antennas are directional and high gain

in nature, thus tending to reduce most undesired interference due to reflected signals [multipath distortion} and ignition noise. In areas where stations are located in different directions from the point of reception, the antenna must be repositioned for optimum reception of individual stations. For this reason,

a good quality rotor is suggested. To minimize the introduction of multipath distortion and ignition interference by the antenna lead-in wires, the use of balanced 300 Ohm [twin lead] cable

is recommended. Unshielded twin-lead is suitable where the lead-in wire length from the antenna is short, and when used

it should be twisted at the rate of 1 to 2 turns per foot. Long lead-in wires can act as omnidirectional antenna and can cancel out the advantages of directional antenna systems. Unshielded twin-lead is also more susceptible to ignition noise than shielded cable.

Exterior FM 75 Ohm Antennas. A second set of antenna terminal is provided for connecting ап unbalanced 75 Ohm antenna cable. These terminals should be used whenever a

75 Ohm coaxial cable is used as a lead-in cable from the

Tuner Power Supply

Plug the power cord plug into the wall outlet, supplying 220V 50 Hz AC. To be sure of protecting the memory information, the power cord plug should be plugged into the outlet even when the stereo system is not in operation. If the AC power to the tuner is interrupted for more than 24 hours (due to power failure, etc.), the memory information will be completely lost.

Control Functions

15)

1 Power Switch. Turns the unit on. Lights up when power

is on.

2 Multipath Switch. When depressed, turns the signal strength indicator function to multipath interference indication. The minimum multipath interference is indicated by minimum indication of the indicators.

3 Multiplex Filter Switch. When depressed, a special filter circuit is introduced to reduce the high frequency noise in weak FM stereo reception. This filter does not affect frequency response but reduces slightly the high frequency stereo separation.

4 Stereo/Mono Switch. Determines the manner in which a received station will be reproduced through the tuner. When listening to a stereo FM broadcast, depressing this switch will cause the unit to mix the left and right channel signal detected from the broadcast and reproduce it through both channels monophonically. The released Stereo setting of this switch will provide automatic stereo FM reception. The mono or stereo mode is indicated by the Mono/Stereo indicators.

5 Scan/Mute/High Switch. This switch should normally be set to released position, especially when you wish to listen to very weak FM stations. In the depressed [High] position, the

mute level during scanning over the band, which a signal must overcome in order to stop the scanning and be heard will be high and only strong signals will be tuned in.

6 Short-Time-Hold [STH] Switch. Used when automatic scanning to resume scanning automatically after tuner has paused on a station for 5 seconds. If you choose to continue listening to that station, depress the Hold pushbutton within

5 seconds.

7 Auto/Manual Switch. Determines the manner of Tuning-Up/ Down pushbuttons usage automatic-scan or manual

Tuner Operation

With the tuner installed properly as outlined, proceed as follows:

FM Tuning. Set the AM/FM switch to FM (pushbutton released). When the tuner is first switched on after plugging the power cord to wall outlet, the lowest FM frequency (87.5 MHz) is tuned. Otherwise, eachtime you turn on the tuner, the previously selected frequency is selected. Set the Auto/Manual switch to Manual (pushbutton released). Press the Tuning-Up switch to tune upscale and press the Tuning-Down switch to tune downscale. Each time either the pushbutton is depressed, the unit is tuned to the next available FM station asignment precisely 50 kHz away. No fine tuning is necessary. To tune upscale or downscale rapidly, press the

14

one-by-one tuning.

8 FM/AM Switch. Selects AM or automatic FM stereo . reception.

9 Memory Pushbutton. Used to preset 7 AM and 7 FM stations for automatic pushbutton tuning.

10 Mode Indicators. Mono, lights up to indicate that the tuner has switched to monophonic FM reception. This indicator is inoperative in AM. Stereo, lights up to indicate that the tuner has switched to stereo FM reception.

11 Signal Strength/Multipath Indicator. Normally used for tuning on both AM and FM bands, with the Multipath switch released. When the Multipath switch is depressed, it can be used as reference to multipath interference.

12 Digital Frequency Display. Shows the frequency of a station to which the unit is tuned directly. Also indicates AM or FM mode and sign to accept the memory presetting.

13 Tuning-Up/Down Pushbuttons, When the Auto/Manual switch is released (Auto position), these pushbuttons will start the automatic-scan to a station either upscale or downscale. When the Auto/Manual switch is depressed (Manual position), each time depressing either of these pushbuttons will tune the unit to the next available station assignment precisely 50 kHz away for FM and 9 kHz for AM.

14 Hold Pushbutton. Used when automatic-scan with the STH button depressed, to stop the scanning at the desired frequency. If the Hold pushbutton is not depressed within 5 seconds after the scan has stopped at a station, the unit will scan automatically to the next station.

15 Memory Pushbuttons. Used for automatic memory pushbutton tuning on AM and FM. Each of 7 pushbuttons may be preset to both AM and FM stations.

either Tuning switch and hold it in position. Release the switch when you have tuned to the desired station. If you tune beyond the ends of the scale the unit tunes automatically to the opposite end and continues.

AM Tuning. Set the AM/FM switch to AM (pushbutton depressed). When the tuner is first switched on after plugging the power cord to wall outlet, the lowest AM frequency (531 kHz) is tuned. Otherwise, each time you turn on the tuner, the previously selected frequency is selected. Set the Auto/Manual switch to Manual (pushbutton released). Press the Tuning-Up switch to tune upscale and press the Tuning-Down switch to tune downscale. Each time either of the pushbuttons is

depressed, the unit is tuned to the next available AM station asignment precisely 9 kHz away. No fine tuning is necessary. To tune upscale or downscale rapidly, press the either pushbutton and hold it in position. Release the button when you have tuned to the desired station. If you tune beyond the ends of the scale the unit tunes automatically to the opposite end and continues.

Automatic-Scan. Іп addition to the manual station tuning by making use of the Manual setting of the Auto/Manual switch, your tuner is equipped with the automatic-scan tuning. Use either manner а or В depending on the selection ofthe STH switch:

а Set the STH switch released (Off). Set the Auto/Manual switch to Auto. Press the Tuning-Up or -Down switch. The tuner will scan to a station and continue receiving that station. To rapidly scan-tune from station to station, press the Tuning-Up or -Down switch for each change.

b Set the STH switch depressed (On). Set the Auto/Manual switch to Auto. Press the Tuning-Up or -Down switch. The tuner will scan to a station and pause on it for 5 seconds.

М you choose to continue listening to that station, press the Hold switch (or release the STH switch). If the Hold switch is not depressed within 5 seconds, the tuner will scan to the next station. Be sure to press the Hold switch if you choose to continue listening to that station.

Pushbutton Tuning. Each of 7 pushbuttons may be preset to an AM station and an FM station for automatic pushbutton tuning (7 AM/7 FM; 14 in all). Set the AM/FM switch to the desired position. Adjust the Tuning-Up/Down switches for the desired station. Press the Memory switch. Now the word Memory appears on the frequency display area to indicate that the unit is ready to accept the memory, for 5 seconds. Press the pushbutton within 5 seconds to set the station. Now the word Memory should disappear from the display. Repeat above steps for each pushbutton. You may later use pushbutton to select the station you wish to hear. If your

Trouble Shooting Guide

The following guides are intended as an aid in correcting the problems you may encounter when setting up the stereo system. Although suggested remedies might seem quite elementary, they may be sufficient to make the corrections without returning the unit to your dealer.

Problem Suggested Remedy

Tuner inoperative, when 1 Check for proper power cord

power switched on. insertion to the wall outlet. 2 Blown internal fuse [Be sure to refer checking to qualified personnel] .

Indicator lights up but no output from the associated amplifier.

1 Check proper program selection on your amplifier. 2 Check proper tuner output connection to the amplifier.

No output one channel. 1 Refer to above. 2 Interchange audio cables to input jacks to check if the same channel remains inoperative.

failed to press the pushbutton within 5 seconds after the Memory pushbutton is depressed, depress the Memory pushbutton again. When the unit is in auto-scan mode, Memory switch is inoperative.

FM Stereo Reception. When tuned to an FM stereo broadcast, the tuner will automatically switch from mono to stereo operation, provided that the Stereo/Mono switch is set to Stereo. Stereo broadcasts are indicated by the

illuminated Stereo indicator. Maximum reduction of background noise on weak stereo stations will be obtained by switching the Stereo/Mono switch to Mono. This will, of course, put the tuner in a monophonic mode of operation. When listening to weak stations, the Scan/Mute switch should be released to prevent the tuner from switching to a mute condition due to reduced signal strength.

FM Multipath Indicator Operation. FM multipath distortion

is caused by a broadcast signal reaching the receiving antenna from 2 directions; #1 direct from broadcaster to the tuner,

#2 the same signal but received as a reflection from a nearby building or other surfaces. This indicator is operative only when receiving an FM broadcast and the Multipath switch is depressed. Set the Multipath switch depressed. Set the AM/FM switch to FM. Adjust the Tuning-Up/Down switches for a fairly strong signal. more than 2 dots of the indicator are

lit, considerably strong multipath interference is

suspected. In cooperation with other people, rotate the antenna mast to position your antenna for minimum indication on the Multipath (Signal Strength) indicator. Proper FM reception free from multipath distortion is indicated by the minimum (ideally none) lighting up on the indicator. To revert to normal signal strength indication, reset the

Multipath switch.

It is recommended that the multipath interference check is made during no modulation condition of the FM broadcast being received, if really possible.

Weak AM reception. 1 Position loopstick antenna for maximum station pick-up.

2 Locate tuner away from metal surface. If building construction uses alminum foil faced instruction, metal lath, or stee! framing, AM reception will be poor.

3 Install external AM longwire antenna. 4 Locate tuner away from TV set as possible. 5 Locate external AM antenna as far away as possible from interfering source.

6 Install proper earth ground.

1 Check all external antenna connections. 2 Install a properly designed antenna. 3 Position receiving antenna for maximum signal.

Weak FM reception.

Multipath distortion. Caused by a broadcast signal

reaching the FM antenna from two

directions; #1 direct from transmitter [broadcast], #2 the same signal but received as a reflection from a nearby building or other surfaces. Install external antenna. Position receiving antenna for minimum distortion [while observing the multipath indicator on the tuner].

1 Install external antenna. 2 Use shielded lead-in wire. 3 Install proper earth ground. 4 Rotate antenna for maximum signal.

5 Connect power line filters to

Noisy FM reception.

Circuit Description

PLL Frequency Synthesizer (Local Oscillator)

The FM local oscillator is comprised of a transistor 03 and a tuning circuit including an oscillator coil T4 and tuning capacitor D4 (varicap diode). The transistor 03 is being oscillated at a frequency of a receive frequency + 10.7 MHz, and its output is applied to the prescaller ІС U6 through a buffer amplifier 04. Тһе prescaller U6 counts down the local oscillator signal frequency into a lower frequency (1/20) suitable for phase comparison in the PLL circuitry. Thus obtained low frequency is applied to the pin 3 of PLL IC U3 through a buffer amplifier 08, and the resultant phase error signal developed at pin 10 is applied to the active LPF filter consisting of transistors 010 and Q11. Finally the filtered error signal is applied to the oscillator tuning capacitor (vari- cap diode) D4 to correct (or to generate a new) oscillating frequency. |

In case of АМ local oscillator operation, the oscillating signal output from the AM oscillator is directly applied to the PLL IC input circuit (pin 3) through a buffer amplifier 09, and the resultant DC error signal is fed back to the AM oscillator tuning diode D6 also through the LPF filter to correct the oscillating frequency.

The FET transistor 057 is а lock-out signal amplifier, the gate of which is connected to the pin 10 of U3 where a lock-out signal is being developed while a phase locked condition is not established in the U3. The transistor 057 amplifies the

Block Diagram of FM IF System IC, U5: *“

interfering appliances.

Stations will not enter memory.

1 Before attempting to enter stations into memory pushbuttons, press the Memory switch. 2 Press memory pushbutton within 5 seconds as Memory indicator is being оп. Scanning will not stop. 1 Be sure to press Hold switch if you are using STH feature.

2 Check antenna connections. Scanning will not stop 1 Set Scan/Mute switch released. on weak stations.

signal and the amplified signal is then rectified by diode D9 and D8 to develop DC voltage to be used for muting control, thus reducing undesirable noises during scanning operation (lock-out condition, etc.).

FM Front End and IF

The FM front end consists of two dual gate FETs and a local oscillator and its buffer. The first FET is used as a FM ВЕ amplifier and the second as a Mixer amplifier. Each gate of the mixer is connected to the RF amplifier output and a local signal injection circuit, respectively. The mixed and resultant IF signals are then led to the IF amplifiers consisting of 05, U4 and U5. The U5 is a multi-function IF system IC including, three stages of limiter/amplifier, FM quadrature detector, meter driver, audio mute signal drive, etc. For further detail of the IC refer to the block diagram shown below.

The detected audio outputs (mono or stereo composite signals) are developed at pin 6 of U5 and applied to the pin 2 of MPX decoder IC. The decoded left and right channel outputs are obtained at pin 6 and 7 of the decoder IC and led to the Tuner Out jacks through low pass filters and one stage of audio amplifier.

METER ORIVE

MUTE ADJ

¥

МРХ Stereo Demodulation

The stereo decoder IC U9 operates as a stereo decoder when it pin 16 is applied by a voltage lower than 1.4V. First in- verter output (pin 6 of U8), which develops a high output with increased antenna signal input, is connected to the transistor base of 018 and makes the 018 conductive when the FM antenna input signal level is increased, then the pin 16 of U9 is grounded through the emitter-collector of 018 and STEREO/MONO switch, resulting in stereo mode of opera- tion or a high voltage during mono mode operation, and these voltages are utilized to make the stereo/mono lamps turn on or off.

When FM antenna signals higher than the stereo threshold level is applied to the antenna circuit, the pin 4 of U8 be- comes low, and this makes 013 conductive (this is a common circuit for stereo & mono LEDs.).

On the other hand if the U5 operate in stereo mode of opera- tion, the pin 9 develops a low output, then the stereo LED will turn on. However, if the pin 9 develops a high output,

Signal Meter

The FM system IC 05 develops a meter drive voltage at its pin 13 and it is led to the pin 2 of IC U10 (meter amplifier/ driver) through the MULTIPASS/METER switch. The U10 amplifies the signal and drives each meter LED connected to its appropriate pin terminals 9 through 13, depending on the signal strength being received.

For AM operation, AM meter drive signal is also connected to the same input pin terminal of No. 2 of IC U10.

Muting Operation

1. FM Muting

The pin 12 of FM IF system IC develops a positive voltage in the event of a low IF input signal level to drive the muting circuit. The positive voltage is first applied to the first in- verter pin 7 of IC U8 and the output is obtained at the second inverter pin 4 (since the first and second inverter is connected in serial, the second inverter output is in phase with the first inverter input). The output is then connected to the pin 21 of the controller ІС U1. The U1 is designed to develop a logic high voltage at its pin 3 when the pin 21 is applied by a logic high voltage. Since the pin 3 is connected to the base of first muting stage of Q19 through the AUTO/MANUAL switch, the Q19 is turned on in the event of low IF input, and this makes all transistors 043, 044, 045 and 046 conductive to the ground, thereby muting out the audio signals.

2. Muting During Scanning Operation

During scanning operation, the muting circuit is also actuated to eliminate undesirable noises caused by scanning operation, since the controller U1 also develops the high level voltage at its pin 3 in addition to the lock-out amplifier output pre- viously stated. And the FM circuit will be muted as described just above.

On the other hand, in the AM circuit the base of 06 is sup- plied from the pin 3 of U1 (logic high) and becomes con- ductive, thereby shorting out the detector output.

the transistor 022, the base of which is connected to the pin 9, is turned on, the cathode side of the mono LED is grounded through collector-emitter path of Q22, thus the mono LED is turned on.

Block Diagram of MPX Stereo Decoder IC:

ia] fos] [21 (|1) PHASE LOCK PLOT STEREO НЕ ЕК жы БЕ

|| 76KHz TO ж 38кн: TO | | 38KHz ТО 38KHz Өк: !экнт DIVIDER Е OVIDER || DIVIDER

LCH POST AMP

Scan Stop Operation

To secure good scan stop accuracy, the scan stop drive signal must have a narrow, sharp characteristic with its center coin- cided with that of IF bandwidth. This will be accomplished as follows:

As already described, during scanning operation, pin 3 of U1 develops a high voltage, and this is applied to the base of Q26 and makes it conductive, then the FET 032 is cut off and the resistor connected across the FET is directly con- nected to R57 in series. The increased resistance makes final IF bandwidth narrow.

In case of AM operation, a fraction of IF output signal is obtained and further amplified by a narrow band additional IF amplifier consisting of amplifiers provided between pin 9 and 10 and pin 11 & 12 of U8. The amplified output is rec- tified by diodes D17 and D18 and the output is led to the inverter provided between the pin 14 and 15 of the same IC. A transistor Q12 also operates as an inverter, the collector of which is connected to the last inverter provided between ріп З апа 2. The output developed at the pin 2 will operate in the same way as that of pin 4 in case of FM operation.

AM Tuner Circuit

Most of the AM tuner circuit are integrated in one mono- lithic U7 consisting of a RF amplifier, local oscillator, mixer, detector, meter driver, etc. For detailed information refer to the block diagram shown below. Incoming antenna signals are applied to the pin 1 of U7 and the final detected audio output is obtained at pin 12, and the amplified audio output is developed at pin 9. The pin 9 output is split into two and applied to each left and right channel LPF filter circuits in the FM MPX stereo circuits through R149 and R150. Transistor 017, the colector of which is connected to the AM audio signal line, is also one of muting circuits.

Block Diagram of AM Tuner IC:

TO SIGNAL METER

SIGNAL METER ORIVE

RF SIGNAL INPUT

Service Information Alignment Procedure

1. Measurement condition 1) Reference temperature: 25°C 2) Reference humidity: 65% | NOTE: Unless otherwise specified, adjustment may be conducted under the room temperature of 5 35°C and the room humidity of 45 85%. 3) Power supply Voltage: AC 220V + 1%, Frequency: 50 Hz + 2%, THD: less than 2%.

2. Test equipment

Any test equipment to be used in this alignment should

have its known accuracy and capability to operate within

a range of specified tolerance described in the electrical

specifications. А! test equipments to be used should be

properly calibrated.

1) FM signal generator:

2) FM MPX stereo modulator

3) Audio signal generator: 20— 20 kHz

4) Audio analyzer (Distortion meter)

5) Audio level meter or

VTVM: 0.5 mV 10V

6) Frequency counter: 200 MHz, high input im- pedance type

7) Oscilloscope: 1 mV/cm or higher

8) Center meter or Null meter

9) DC voltmeter: High input impedance type

10) FM dummy antenna

30 200 MHz

3. Operation and standard setting 3.1 Operation of controls and switches

a) POWER (power switch): This switch makes the se- condary of the power transformer open or close. In the off mode the back-up current is available for the me- mory, which is indicated by LED indicator. When the power plug is taken off the AC outlet, the memory will be erased after 24 hours.

b) MULTIPATH (multipath switch): This switch is used to indicate the multipath distortion by the LED meter by depressing the switch. The FM antenna should be adjusted to achieve the minimum distortion. By re- leasing this switch the LED meter on front panel serves for normal signal strength indication.

c) MPX -FIL (multiplex filter): When depressed this pushbutton activates a circuit which reduces high fre- quency noise in weak FM stereo reception. This filter does not affect frequency response but reduces slightly the high frequency stereo separation.

d) STEREO/MONO (mode switch): Determines the manner in which a received station will be reproduced by tuner.

STEREO (released): Provides stereophonic reception of any stereo broadcast. This pushbutton also provides automatic FM stereo reception.

MONO (depressed): Тһе left and right channel signals detected from FM broadcast are mixed and reproduced through both channels.

в) SCAN LOW/HIGH LOW: Releasing of this pushbutton will introduce a special muting circuit which eliminates noise between stations on FM when scanning.

HIGH: Maximum reduction of background noise on weak stereo stations will be obtained by depressing the SCAN LOW/HIGH pushbutton. This will, of course, put high frequency component in the program material in a monophonic reproduction. In this position, the mute is switched off to prevent the tuner from switch- ing to a mute condition due to weak signal strength. San stop level is as shown: , ЕМ LOW: 20 + 4 dBf

HIGH: 38 + 3 dBf АМ LOW: 57 + 2 dBu/m

HIGH: 67 + 3 dBu/m

f) STH (short-time-hold pushbutton): When depressing the UP or DOWN for automatic scanning, a pause for 5 seconds should be provided by depressing this push switch before resuming scanning. As long as this switch is depressed 5 seconds pause shall be repeated.

9) UP/DOWN (tuning pushbutton): When the AUTO/ MANUAL pushbutton is set to AUTO position, it will start scanning either upward or downward the receive frequency.

When the AUTO/MANUAL pushbutton is set to MANUAL position, at each time of depressing either of the pushbuttons {һе receive frequency will be tuned to the next available station assignment by 50 kHz (U.S.A. 200 kHz) spacing for FM and 9 kHz (U.S.A. 10 kHz) spacing for AM.

Keep depressing either of pushbuttons more than 1 second, receive frequency varies serially, and stop when release the pushbutton.

h) AUTO/MANUAL (tuning mode pushbutton): De-

5. FM alignment 5.1 Receive frequency preset Preset the following frequencies to memory before start- ing all alignment procedures: (1) 87.5 MHz (2) 90.0 MHz (3) 98.0 MHz (4) 106.0 MHz (5) 108.0 MHz (6) 108.0 MHz 1) To preset memory a) Frequency indicator reads either 87.5 MHz or 108.0 MHz when turning power on. Push memory preset switch from 1 7. b) Keep depressing either UP or DOWN in MANUAL mode. As the frequency approaches to the designated fre- quency, temporarily release the button. Then press it step by step to tune exactly to the frequency, where MEMORY button should be pushed before pushing one of the 7 buttons. c) Check the frequencies above have been preset cor- rectly on each pushbutton. 5.2 PLL local oscillator circuit alignment 5.2.1 Reference frequency adjustment 1) Connect frequency counter to TP-3. 2) Adjust CT-7 for 11.5200 MHz + 100 Hz.

termines the mode of electronic tuning automatic scanning (AUTO) or manual one-by-one tuning (MANUAL).

In MANUAL mode the receive frequency is selected channel after channel by UP or DOWN pushbutton, enabling a weak antenna input below the muting level to be received.

In AUTO mode scanning starts when UP or DOWN switch is depressed, scanning halts where the level of antenna input exceeds a certain value which is nearly equivalent to the muting level.

In AUTO scanning, scanning function prevails, defeat- ing the memory function.

i) FM/AM: Selects AM or automatic FM stereo reception. When depressed it selects automatic FM stereo reception and when released it selects AM reception.

j) MEMORY: Used to preset AM and FM stations for automatic pushbutton selection. When this switch is depressed “MEMORY” is indicated for 5 seconds. By pushing in one of 7 memory preset buttons during this 5 second period the frequency on the display is memorized.

k) 1 7 (preset pushbutton): Used for automatic memory pushbutton tuning on AM and FM. Each of 7 push- buttons may be preset for both AM and FM stations individually.

|) HOLD: Used to stop scanning at the desired frequency while scanning automatically.

4. Memory back-up check: Confirm 8V at emitter of 0-25 for the back-up current while the AC power source is off. Use a low resistance tester or connect approximate 5 КОћт resistor between + terminals when confirming the back-up current. ;

5.2.2 Vari-cap control voltage adjustment 1) Connect voltmeter between TP-4 and GND.

2) Depress preset-button 5 or 6 (108.0 MHz), adjust CT-4 for 9.6V.

3) Depress preset-button 1 (87.5 MHz), adjust T-4 for 3.4V.

4) Depress preset-button 5 or 6 (108.0 MHz), adjust CT-4 for 10.0V

5) Depress preset- -button 1 (87.5 MHz), adjust T-4 for 3.4V.

6) Repeat steps 4) and 5) until 10.0V + 0.1V is obtained at 108.0 MHz and 3.4V + 0.2V at 87.5 MHz. NOTE: Use high input impedance Voltmeter. If procedure in step 2) will not provide result as indicated, adjust T-4 first. 5.3 RF IF circuit adjustment Connect Voltmeter (low impedance type) between TP-1 and TP-2. Output deviation of signal generator should be - within +2 kHz. 5.3.1 IF adjustment 1) Set signal generator to 98.000 MHz, depress preset- button 3 (98.0 MHz). Adjust T-12 for Voltmeter read- ing within +20 mV. 2) Connect level meter to output terminal, adjust T-5, T-6 for maximum receive sensitivity by reducing the output of the signal generator.

5.3.2 Front End adjustment (Sensitivity adjustment)

1) Set signal generator to 90.000 MHz, depress preset- pushbutton 2 (90.0 MHz). Adjust T-1, T-2, T-3 alter- nately for maximum scope display.

2) Set signal generator to 106.000 MHz, depress preset- pushbutton 4 (106.0 MHz). Adjust СТ-1, СТ-2 and CT-3 for maximum scope display.

3) Repeat steps 1) and 2) until maximum scope display is obtained at both frequencies.

4) Adjust CT-7 to obtain maximum sensitivity if wave form is not symmetrical.

5.3.3 Distortion adjustment

1) Set signal generator to 98.000 MHz, depress preset- button 3 (98.0 MHz). Antenna input level: 65 dBf

2) Adjust T-13 to obtained minimum distortion on THD meter.

5.4 MPX circuit adjustment Connect MPX signal generator to standard signal generator. Test circuit sets up as shown:

FREQUENCY COUNTER

TUNER

PIN 9 OF U6

98.0 MHz £2KHz ANT. INPUT: 65 dBf

( NO MOD.)

19.00 KHz + 50Hz

MODE. STEREO

ADJUST RV 6 FOR 19 OKHz+50Hz

5.4.2 Separation adjustment

1) Apply 65 dBf MPX signal to antenna input.

Rotate RV-5 for minimum reading on right channel Voltmeter.

2) Apply 65 dBf MPX signal generator output level modu- lated with 1 kHz right channel signal to antenna input. Check for minimum reading on left channel Voltmeter.

3) If leakage on each channel is not equal, rotate RV-7 to a point at which provides equal leakage on both channels.

5.4.3 Stereo level check

1) Feed signal generator modulated with standard stereo signal by MPX signal generator to antenna terminal.

2) Check that stereo indicator lights up at antenna input level between 16 dBf and 24 dBf.

6. AM alignment 6.1 Receive frequency preset Preset the following frequencies to memory before initiat- ing adjustments: (1) 531 kHz (2) 603 kHz (3) 999 kHz (4) 1404 kHz (5) 1602 kHz 6.2 PLL local oscillator circuit 6.2.1 Vari-cap control voltage adjustment

11

3) Check that voltage between TP-1 and TP-2 is within

+20 mV with no signal condition. 5.3.4 Muting level adjustment

1) Apply 38 dBf level to antenna input. Set the AUTO/ MANUAL Selector pushbutton to AUTO (pushbutton released) and the SCAN HIGH/LOW selector to HIGH (pushbutton depressed).

Rotate RV-1 fully clockwise (RV-1 is located on PSSW213).

2) Depress any one of memory preset pushbuttons, rotate RV-1 counterclockwise until mute is cancelled (when readjusting, depress the preset pushbutton each time). NOTE: If above procedure is inadequate, rotate RV-1

to a point at which the level turns low to high.

3) Set the SCAN LOW/HIGH selector pushbutton to LOW (pushbutton released), then check that mute is cancel- led at 20 dBf + 4 dBf.

5.4.1 19 kHz (76 kHz VCO) adjustment 1) Set MONO/STEREO selector pushbutton to STEREO (pushbutton released). 2) Set signal generator output to 65 dBf (no modulation). 3) Rotate RV-6 for frequency reading of 19 kHz + 50 Hz at IC U-9 #9 pin, then fix RV-6.

5.4.4 Signal indicator adjustment 1) Apply 60 dBf signal to antenna input. Adjust RV-5 so that all of 5 indicator dots light up. 2) Apply 20 dBf to antenna input. Check that the 151 dot lights up. 3) Check that no dot lights up with no antenna input. 5.4.5 Multipath indicator check 1) Apply 45 dBf signal AM modulated 50! . MUTIPATH button. 2) Check 4 dots of indicator light up. 3) No dot should light up or only 1st dot may light up when readjusting signal generator to FM mode modu- lated with 40 kHz deviation.

Depress

1) Connect Voltmeter between TP-4 and GND. 2) Depress preset-button 5 (1602 kHz), adjust CT-6 for 9.2V. 3) Depress preset-button 1 (531 kHz), adjust T-8 for 1.6V. 4) Repeat steps 2) and 3) until 1.6V + 0.05V is obtained at 531 kHz and 9.2V + 0.1V at 1602 kHz. NOTE: Use high input impedance Voltmeter. If procedure in step 2) will not provide result indicated, adjust T-8 previously.

6.3 IF adjustment Use procedure (A) or (B). (A) Connect IF sweep input to output jacks. Connect IF sweep to AM antenna terminal. Adjust Т-9 for ‘correct’ wave form as shown.

Х

(non-linear) (correct)

(B) Connect IF sweep input to IC U-7 #12 pin. Connect IF sweep output to AM antenna terminal. Adjust T-9 for higher and wider wave form on dis-

play. cue

450 kHz

6.4 Sensitivity adjustment

1) Pull out bar antenna away from rear panel.

2) Connect test loop antenna to signal generator and locate the loop antenna 20 30 cm from bar antenna. Con- nect VTVM or level meter and oscilloscope to tuner output.

3) Adjust signal generator to 603 kHz, 1 kHz modulated 30%, depress preset-button 2 (603 kHz). Rotate core in bar antenna for maximum sensitivity.

4) Adjust signal generator to 1404 kHz, depress preset- button 4 (1404 kHz).

Adjust CT-5 for maximum sensitivity.

5) Repeat steps 3), 4) until maximum sensitivity is ob- tained at both 603 kHz and 1404 kHz.

6) Check that the sensitivity is within the specifications at 999 kHz, and the output level is +3 dB.

6.5 Signal meter adjustment Increase signal generator output to 80 dBu. Adjust RV-2 so that all of 5indicator dots light up (use 200 pF antenna). 6.6 Scan-stop circuit adjustment

1) Apply 57 dBu* 999 kHz signal generator 400 Hz modu-

lated 30% output from test loop antenna positioned

O

12

(unsymmetrical)

NOTE: Check the marker is approximately at the center which is 450 kHz. Do not apply overloads level input. Adjust T-10 for maximum and symmetrical wave display.

60 cm from unit bar antenna.

* = Signal generator scale 83 dBucontaining 26 dBu

loop antenna loss.

2) Set the unit to AUTO mode, SCAN LOW/HIGH to LOW. Rotate RV-3 fully counterclockwise.

3) Depress preset-button, then rotate RV-3 clockwise unit! the level is