Kenwood-AG-203-Service-Manual(1) 电路图 维修手册.pdf

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1、 Trio AG-203 CR Oscillator Instruction Manual Contents Features 3 Specifications 4 Circuit Description 6 Panel Controls and Their Functions 8 Operating Instructions 10 Applications 12 Maintenance 15 Adjustment 16 Caution 17 Parts List 18 PC Board 21 Schematic Diagram 22 Features All solid-state circ

2、uitry ensure extreme high stability, minimum warm-up time and less power consumption. High reliability with adoption of direct coupled circuits throughout the entire stage. Compact styling with vertical type panel for easy operation. Frequency dial scale calibrated with single-scale graduations for

3、frequency range 10Hz to 1MHz selectable in 5 ranges. High output design; more than 7V rms at no load and more than 3.5V rms at 600. Output level is fully adjustable with a 10dB step, 6 range attenuator and a level indicator. Low output impedance of 600. The attenuator provides accuracy of 1dB at 600

4、 load. Sine and Square waves easily available. Synchronizing input terminal. Extremely high stability against variation of power source. RadioFans.CN 收音机爱 好者资料库 Specifications Frequency Range x 1 range; 10Hz 100Hz x 10 range; 100Hz 1KHz x100 range; 1KHz 10KHz x 1K range; 10KHz 100KHz x 10K range; 10

5、0KHz 1MHz Frequency accuracy (3% 1Hz) (Sine Wave Characteristics) Output voltages (no-load) 7V rms or more Frequency Characteristics (reference freq. 1KHz) 10Hz 1MHz, 1dB Distortion Factor 400Hz 20KHz, 0.1% or less 100Hz 100KHz, 0.3% or less (x 10 range for 100Hz) 50Hz 200KHz, 0.5% or less 20Hz 500K

6、Hz, 1% or less 10Hz 1MHz, 1.5% or less (Square wave characteristic) Output Voltage (no load) 10V p-p or more Sag: 5% or less at 50Hz Rise and Fall times: 200ns or less Overshoot: 2% or less (at 1KHz, max output) Duty ratio: 50% 5% (at 1KHz, max output) (External Synchronization Characteristics) Sync

7、hronization range: 1V Max, allowable input voltage: 10V rms Input impedance: Approx 10K Output impedance: 600 10% Output attenuator: 0dB, -10dB, -20dB, -30dB, -40dB, and 50dB in 6 steps (accuracy: 1dB at 600 load. (Stability against power source voltage variation (with respect to variation of 100V 1

8、0%) Frequency drift: Within 5% Output Voltage Variation: Within 0.5dB Operating Temperature: 0-50(relative humidity less than 90%) Power Requirements: AC 100V (120V, 220V or 240V), 50- 60Hz Power Consumption: 5 Watts External View: See Fig. 2 on page 9 Dimensions: Casing 128(W) x 238(D) x 190(H)mm.

9、Overall (including knobs); 130(w) x RadioFans.CN 收音机爱 好者资料库 268(D) x 215(H)mm. Weight: 2.9kg. Accessories: Power cord (1) Output cord; one red and black test cord with basket clip and antenna plug. Banana plug; red (1) and black (1) Fuse; 0.125A (2) and 0.2A (2) Instruction Manual (1) Circuit Descri

10、ption 1. Summary When reading the following descriptions, refer to the block diagram (Fig. 1) and the schematic diagram. The sine-wave signal generated by the Wien bridge oscillator circuit is fed through the WAVE FORM selector switch set at the position to the OUTPUT control, by means of which it i

11、s adjusted to any desired voltage. If the WAVE FORM switch is in the “ _ _ ” position, the sine-wave signal is shaped into the square wave and the voltage is also adjusted by the OUTPUT control. The signal voltage thus adjusted is applied to the output circuit, where its impedance is appropriately c

12、onverted, and then delivered through an output attenuator to the output terminal. The attenuator provides selectable attenuations of 0dB through -50dB in 10dB steps at 600 of output impedance. 2. Wien Bridge Oscillator Circuit The Wien bridge oscillator circuit elements consist of the resistance ele

13、ments, which may be switched over for 5 ranges by the FREQ. RANGE switch, and the variable capacitor controlled by the FREQUENCY dial. These elements provide means to vary the oscillating frequency continuously over 10 times its frequency on one range, thus determining any desired frequency within t

14、he entire frequency range from 10Hz to 1MHz. The amplifier circuit for the oscillator circuit is composed of a 2-stage differential amplifier and an output stage, employing an DC amplifier circuit. The first stage is a high input impedance circuit with FET while the driver stage is a wide band, high

15、 amplification type circuit with PNP transistors featuring high cut-off frequency. The output stage is a SEPP circuit using complementary transistors. The output voltage is fed back with positive polarity through the oscillator elements to form an oscillating circuit, while it is also fed back with

16、negative polarity through the non-linear thermistor to stabilize the amplitude. 3. Square Wave Shaping Circuit The square wave shaping circuit is a Schmidt-trigger circuit in which the sine wave signal from the oscillator circuit is shaped into a square wave. It is composed of an emitter coupled Sch

17、midt-trigger circuit and a buffer amplifier, thus providing sufficient rising and falling characteristics. RadioFans.CN 收音机爱 好者资料库 4. Output Circuit The output circuit converts the impedance of signal from the OUTPUT control and feeds the signal to the output attenuator at a low impedance. It is a S

18、EPP-OCL circuit employing complementary transistors to provide sufficiently low output impedance characteristics over the range from DC to 1MHz. 5. Output Attenuator The 6-position output attenuator selects attenuations of 0dB to -50dB in 10dB steps. At the 0dB position with the OUTPUT control turne

19、d fully clockwise, the output voltage (sine wave at no-load time) is more than 7V rms. The output impedance is rated for 600 and the attenuation accuracy is as high as 1.0dB at a 600 load. 6. Power Supply The Power supply circuit is powered by AC (100V, 120V or 220V) and delivers DC 22V sufficiently

20、 stabilized by large capacity smoothing capacitors (220OmF x 2) and a voltage stabilizer. Panel Controls and Their Functions The table below describes the functions of panel controls. Refer to the panel diagram on page 9. (Fig 2) FRONT PANEL This lamp (light emitting diode) lights when POWER switch

21、(2) is ON. 2. POWER Pushbutton type switch turns on the power when pressed. 3. ATTENUATOR 6-position output attenuator selects attenuations of 0dB to -50dB in 10dB steps. 4. OUTPUT Output terminal used for both sine wave and square wave. The marking indicates GND (case grounded). 5. WAVE FORM Output

22、 waveform selector switch. When pressed to “”, output signal is sine wave. When pressed to “_ _ ” the signal is square wave. 6. FREQ. RANGE Oscillating frequency range selector switch which selects the ranges in 5 steps as follows: X 1 10Hz -100Hz x10 100Hz- lkHz x100 1kHz - 10kHz x 1K 10KHz 100KHz

23、x 10K 100KHz 1MHz 7. Amplitude Amplitude adjuster to continuously vary the amplitude of output voltage. 8. FREQUENCY DIAL This dial adjusts oscillating frequencies. Frequencies can be read by multiplying the reading on the dial scale by magnification of FREQ.RANGE. 9. DIAL SCALE This dial is calibra

24、ted with graduations of 10-100 to indicate oscillating frequencies. 10. DIAL POINTER This pointer indicates frequencies on the dial scale. REAR PANEL 11. Sync. External synchronizing signal input terminals fir GND for connection of synchronizing signal to AG-203. 12. Fuse Fuse fore Power supply. 13.

25、 A.C. Connector For connection of the supplied A.C. connector. 14. Power Voltage Selector. This selector is preset to 240V position. A.C. power of 100V, 120V or 220V may be used by changing the position of the selector. Operating Instructions 1. Start-up First check that the fuse (12) and the power

26、voltage selector (14) are in the normal positions, then connect the supplied AC power cord to your AC outlet. Press the power switch (2) and the pilot lamp (1) will light indicating that the unit is ready for operation. Allow 2 or 3 minutes for the unit to warm up so that it is stabilized. 2. Wavefo

27、rm Selection Press the WAVE FORM switch (5) to the position to obtain sine waves. Press the switch to the _ _ ” position for square waves. 3. Frequency Selection First set the FREQ.RANGE switch (6) to the desired range, then set the frequency dial (8) so that the dial pointer (10) indicates your fre

28、quency. Example: Suppose you want to select a frequency of 1.5kHz, then proceed as follows: 1. Set FREQ RANGE switch (6) to x 100 2. By using the frequency dial, set the dial pointer (10) to “15” on the dial scale. The frequency thus selected is: 15 x 100 = 1500(Hz = 1.5(kHz) 4. Adjustment of Output

29、 Voltage The output voltage from OUTPUT terminal (4), be it sine wave or square wave, can be continuously varied by AMPLITUDE (7) and stepped down by ATTENUATOR (3). Example: To adjust output voltage to 10mV rms, proceed as follows: 1. Connect a voltmeter capable of measuring AC 1 V rms to OUTPUT te

30、rminal (4). 2. Set ATTENUATOR (3) to 0dB and then adjust AMPLITUDE (7) until the voltmeter indicates 1V rms. A voltage of 1V rms will appear at OUTPUT terminal (4). 3. Set ATTENUATOR (3) to -40dB. The voltmeter indicates about 0V, while a voltage of 10mV rms appears at OUTPUT terminal (4). 5. Use of

31、 Synchronizing Input Terminal By applying an external sine wave signal to SYNC terminal (11), the oscillating frequency of AG-203 can be synchronized to the external signal. The synchronizing range is increased in proportion as the input voltage is increased as shown in Fig. 3, indicating that the s

32、ynchronizing range is about 1 % per input voltage of 1 V. Example: Suppose that the input signal voltage is 1V rms and the oscillating frequency of AG-203 is between 990Hz and 1010Hz (1kHz 1kHz x 1%/V x 1V = 1kHz 1kHz x 0.01), the frequency can be synchronized with 1 kHz of the input signal. Note th

33、at too high a synchronizing signal voltage will affect the amplitude and distortion factor, and care must therefore be taken when the signal voltage is higher than 3V rms. Also, note that if the synchronizing signal is largely deviated from the frequency of AG-203, the synchronization is pulled out

34、which affects the distortion factor. It is therefore advisable that the oscillating frequency be first synchronized with a low input signal voltage (less than 1 V rms) and then the voltage be increased. Applications 1. Using as Sine Wave Oscillator AG-203 can be used as a sine wave oscillator as out

35、lined below. 1.1 Since the unit features low distortion factor, it can be used for measurement of distortion characteristic of amplifier. 1.2 Since the unit features wide bandwidth, it can be used for measurement of frequency characteristic of amplifier. 1.3 The built-in high accuracy attenuator per

36、mits measurement of amplifier gain. 1.4 Can be used as a signal-source of impedance bridge. 2. Measurement of Amplifier Gain An example of measurement of amplifier gain is described below. First connect AG-203, amplifier to be tested and AC volt-meter as shown in Fig. 4. 1 . Adjust ATTENUATOR (3) an

37、d AMPLITUDE (7) so that AC volt-meter indicates the rated output (supposed to be 1V in this example) of the amplifier. To facilitate the measurement, it is advisable to set ATTENUATOR (3) as low as possible. Assume that ATTENUATOR (3) is set 50dB for the rated output. 2. Disconnect the amplifier and

38、 connect the AC volt-meter to AG-203 to measure the output voltage. Note that the use of ATTENUATOR (3) eliminates the need for connecting a high sensitivity voltmeter. If ATTENUATOR (3) is set to 0dB and the voltmeter indicates 2V, it means that the input voltage of the amplifier is 50dB below 2V.

39、Therefore, the gain obtained is as follows: 50dB + 20 10 1V gdB 2V lo = 50dB 6dB = 44dB 3. Measurement of Phase Characteristic Connect AG-203 and an oscilloscope to the amplifier to be tested as shown in Fig. 5. If there is no phase shift about the output signal of the amplifier, the oscilloscope wi

40、ll display a straight line as shown in Fig. 5A. If the straight line on the oscilloscope is curved at its top and bottom sections as shown in Fig. 5B, it indicates that the output signal of amplifier is suffering from an amplitude distortion. In this case, reduce the output level of AG -203 a little

41、 to vary the frequency. This causes the straight line on the oscilloscope to expand gradually to turn into an ellipse. By utilizing the configuration of this ellipse, the phase shift can be calculated as follows: First, measure the maximum horizontal deflection and suppose that this deflection is X”

42、 and that the section at which the ellipse crosses the horizontal axis is “x, as shown in Fig. 6. And, the phase shift angle is given by the following. x Sin = X Find from the table of trigonometric functions and the value obtained gives the angle of phase shift. 4. Using as Square Wave Oscillator f

43、alling characteristics (120 ns as standard 1. Connect AG-203, an amplifier to be tested and an oscilloscope as . Press WAVE FORM (5) to the “_ _ ” position to obtain square waves . During the test, change the frequency as necessary. The relationship Maintenance . Removal of Case the left, right and

44、top sides with a Phillips head screwdriver. . Mounting the Case e underside of it is left open a little. Tighten 6 screws uniformly. Do not use excessive force when tightening, as it will damage the screws and the vinyl leather on the case. AG-203 features excellent rising and characteristic). It ha

45、s no coupling capacitors in the output stage, so the sag (deflection of top section) is as low as 5% at 50Hz. By applying such a good square wave to an amplifier input, various characteristics of amplifier can be observed on an oscilloscope. To test an amplifier, proceed as follows: shown in Fig. 7.

46、 2 of appropriate frequency and amplitude. 3 between waveforms and amplifier characteristics is shown in Fig. 8. 1 Remove 2 screws each on Lift the case at the underside until the case is fully removed (see Fig. 9). 2 Placthe case so that the 3. Replacement of Fuse fuse with one Adjustments ll the c

47、ircuits of AG-203 are factory adjusted prior to shipment and no further adjustments are required, except for the frequency dial which may need readjustment for proper tracking. Although this dial is also pre-adjusted at the factory. If adjustment is required, proceed to the adjusting work using an a

48、ccurate test knob of the frequency dial, then loosen the equency counter indicates 1 kHz. 4. s it is. Check that the frequency 5. Open the fuse holder with a Phillips head screwdriver. Replace the having the same rating. A re equipment. Note that the power supply voltage must be calibrated before ma

49、king adjustment (see Fig. 10). 1. Connect a frequency counter to OUTPUT terminal (4). 2. Remove the set-screws on the dial. 3. Set FREO. RANGE switch (6) to X 100 and adjust the shaft of the dial until the fr Set the dial to 10 position and tighten the setscrews, making sure that the shaft stays a counter is indicating 1 kHz, then secure the knob to the di