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1、OSCILLOSCOPE OS-9020G SERVICE MANUAL LG Precision Co., Ltd. _._ _ - ,.e-7 . ._l_l .-. ._._. . .- ._-.- RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 Servicing Precautions Please read all instructions in the service manual throughly before servicing. Disconnect power cord from power source before o
2、pening the enclosure. Instructions 1. 2. 3. 4. To maintain the precision and reliability of the product use it in the standard setting (temperature 10 o-35 o centigrade, humidity 45%-85%) After turning on power, please allow a 15-minute pre-heating period before use. Triple-line power cord is to be
3、used for the product. But when you are using the doubleline cord,make sure to connect the earth terminal of the product to the earth at the power source for safety. For quality improvement the exterior design and specifications of the product can be changed without prior notice. Warranty Warranty se
4、rvice covers a period of one year from the date of original purchase. In case of technical failure within a year, repair service will be provided by our service center or sales outlet free of charge. We charge for repairs after the When the failure is a result of accident, we charge for repairs Noti
5、ce one year warranty period expires. users neglect,natural disaster or regardless of the warranty period. This Serivce Manual describes the most typical product of this model. If there are any specific differences between this Manual and the servicing unit, please contact Goldstar Precision sales of
6、fice in your area. LG P r e c i s i o n Co-,IdtcA -_-._-.-.- _._. RadioFans.CN 收音机爱 好者资料库 C O N T E N T S G E N E R A L . . . S P E C I F I C A T I O N S . A C C E S S O R I E S. P R E V E N T I V EM A I N T E N A N C E . C I R C U I TD E S C R I P T I O N . . . C A L I B R A T I O N . . . 6-l.Calib
7、ration Interval . 6-2.Test Equipment Required. . 6-3.Preliminary Procedure. . 6-4.Preliminary Control Settings . 6-5.Initial Starting Procedure. . 7, 8* Q* S E M I C O N D U C T O R L E A D C O N F I G U R A T I O N S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 E L E C T R I
8、 C A L P A R T S A R R A N G E M E N T 4) Humidity range for rated operation 45% to 85% RH 5) Max.ambient operating humidity 35% to 85% RH 7 ._- I_ .-_ _._ _._.ll- -l_-.,._.i-l. .-.- . . .-._1 3*A C C E S S O R I E S (1) Cable (BNC to CLIP) -_-_-_-v-W- 1 (2) Probe (Option) -_-_-_-_-2 (3) Fuse ( 2A f
9、or100V or 120V set or 1A for 220V and 230Vset ) _- 1 (4) Power supply code -_-_-_- 1 (5) Operation manual -_-_-_-_-_-_- - 1 8 4,P R E V E N T I V E M A I N T E N A N C E Preventive maintenance,when performed on a regular basis, can prevent instrument breakdown and may improve the reliability of the
10、oscilloscope. The severity of environment to which this instrument is subjected will determine the frequency of maintenance.A convenient time to perform preventive maintenance is preceding recalibration of the instrument. Disassembly Remove the top cover and the bottom cover of the instrument. Most
11、of the internal parts of the instrument are now accessible, if access to the front of the circuit board are necessary, remove the knobs from the external control shafts on the board. Cleaning The instrument should be cleaned as often as operating conditions require.Accumulation of dirt in the instru
12、ment can cause component breakdown. The covers provide protection against dust in the interior of the instrument. Loose dust accumulated on these covers can be removed with a soft cloth or small brush. Dirt that remains can be removed with a soft cloth dampened in a mild detergent and water solution
13、.abrasive cleaners should not be used. Cleaning the interior should only be occasionally necessary. The best way to clean the interior is to blow off the dust with a dry, low- velocity stream of air.A soft-bristle brush or a cottontipped applicator is useful for cleaning in narrow spaces or for clea
14、ning more delicate components. Visual Inspection The instrument should be inspected occasionally for such defects as bracken connections,improperly seated transistors, damaged circuit boards, and heat-damaged parts.the corrective procedure for most visible defects is apparent ; however, particular c
15、are must be taken if heat-damaged components are found.Overheating usually indicates other trouble in the instrument ; therefore, correcting the cause of the overheating is important to prevent recurrance of the damage. - _. - .-.-.-. 5.C I R C U I T D E S C R I P T I O N The block diagram ( page 51
16、 1 shows the overall relationship between all of the circuits. Complete schematics of each circuit are also given in section schmatics diagrams ( page 52 to 68 1. Refer to these diagrams throughout the following circuit description for electrical values and relationship. 1 ATTENUATOR j Signals appli
17、ed to the input connector can be either AC coupled or they can be disconnected to the internal circuit when S201 ( GND position. or DC coupled, S301 1 is Attenuation is determined by the setting of the VOLT / DIV switch. The attenuator that is controlled by the VOLT / DIV switch has +1/2, +l, s10,31
18、00 circuit. s2, -5,-10 circuits are in RA201 ( RA301 and +10, -100 circuits are between S202 ( S302 1 and S203 ( S303 1. CH1 (CH21 INPUT AMPLIFIER Signal from the input attenuator is connected to source follower QZ01 ( Q301 1. When excessively high-amplitude signals are applied to the source followe
19、r, the signals will be Q202 ( Q302 ) and the gate-source junction of Q201 ( Q301 1. When S202D ( S302D is open ( PULLX5MAG 1, the signal that is feed back to OP AMP through R23Q ( R328 ) amplfies the output signal of Q204 ( Q304 by 5 times. And the signal of Q206 ( Q306 ) base is converted from a si
20、ngle-ended signal to a paraphrase signal by differential amplifier. CH1 (CH2 1 PRFJWP 513-547 used only) D I S P L A Y Control Setting Preset the controls as given in the Preliminary Control Setting. 141 Check/Adjust CRT Bias. Set the TIMWDIV switch to the 1mS a. Rotate the INTHNSITY to the directio
21、n of 10 oclock as shown. INTEN 16 b. Observe the trace of CRT. c. Adjust the CRT Bias Adjustment VR617 so that the trace makes an appear. 151 Check/Adjust Trace Rotation. a. Check that the trace is parallel to the horizontal center line. b. Adjust the TRACE ROTATION for a trace that is parallel with
22、 the horizontal graticule lines. 61 Check/Adjust ASTIGmatism and FOCUS a. Vertical Mode switch to the CH2 X-Y1 position, and Display switch to the X-Y1 position, and AC-GND-DC to GND. b. Set the INTENSITY control for a small spot, as the following figure,using position controls. The SDot o fscreen c
23、. Check that the spot is round. d. Adjust the FOCUS adjustment and ASTIG adjustment VR616 for a round spot. 17 H O R I Z O N T A L S Y S T E M Control settings Preset the controls as given in the Preliminary Control Settings. 71 Check/Adjust Horizontal Gain. a. Set the input AC-GND-DC to DC. b. Set
24、the TIME/DIV switch to the lms. c. Check that the time marks align with the graticule line over the center eight DIVisions, within 3%. d. Adjust the H GAIN adjustment VB611 so that the time marks align with the center eight graticule lines. C83 Check/Adjust Horizontal X 10 MAG Gain. a. Set the TIME/
25、DIV switch to the 1mS. b. Set X 10 MAG ( Pull out the VARIABLE control 1. c. Check that the one-cycle time marks align with the ten division graticule lines, within 5%. d. Adjust the MAG GAIN adjustment VR612 so that the one-cycle time marks align with the ten division graticule lines. e. Push in th
26、e VARIABLE control after check and adjustment. 91 Check/Adjust MAG CENT. a. Set the TIME/DIV switch to the 1 mS. b. Being the VARIABLE control is in pulled out state ( Xl0 MAG , the left end of the trace is brought to the center point and then the VARIABLE is depressed. c. Observe the movement of th
27、e left end of the trace. d. Adjust the MAG CENT adjustment VR614 for the movement of the end of the trace within f 0.2DIV. Cl01 Check/Adjust low spaced sweep accuracy. a. Set the time mark generator for 5mS time marks. b. Set the TIME/DIV switch to 5mS. c. Check that the time marks align with the gr
28、aticule line over the middle eigth divisions, whth 3%. d. Adjust the 5mWDIV adjustment VR606 so that the time marks coincide with the middle eight graticule lines. Cl11 Check/Adjust High speed sweep accuracy. a. Set the input coupling switch to DC. b. Set the time mark generator for 10s time marks.
29、c. Set the TIME/DIV switch to the 10s. d. Check that the time marks align with the graticule lines over the middle eigh divisions. e. Adjust VC601 that the time marks coincide with middle eight graticule lines. 18 V E R T I A C A L S Y S T E M Control settings Preset the controls as given in the Pre
30、liminary Control Settings. Cl41 Check/Adjust DC Balance ( Step attenuator balance 1. a. Set the VOLTWDIV switch to the 5mV position. b. Position the trace to the horizontal center line. c. Change the PULL x5MAG switch to the 1mV position. d. Check that the trace is within 0.1 division of the horizon
31、tal center line. e. Adjust the CH1 ( CH2 DC BAL adjustment,VRZBl ( CH1 or VR301 ( CH2 1, for a trace at the horizontal center line. f. Repeat part (a through (e) until less than 0.05 division shift is noted when changing the VOLTWDIV setting. Cl51 Check/Adjust ADD BALANCE. e. f. i. Set the TIME/DIV
32、switch to the 1mS position. Set the CH1 and CH2 AC-GND-DC switches to GND. Set the V-MODE switch to CHlI. Next, Adjust the vertical Position control that the trace is identical with the horizontal center graticule line. Set the V-MODE switch to CCH21. Next, Adjust the vertical Position control that
33、the trace is identical with the horizontal center graticule line. Set the V-MODE switch to ADD. Check that the trace is identical with the horizontal center graticule line within f 0.5 division. Adjust the ADD BALANCE adjustment VR501 for two times of the difference with the horizontal center gratic
34、ule line. 161 Check/Adjust Vertical Position Center. a. Confirm the vertical POSITION control at the midrange. b. Check that the trace is within 1 division. c. Adjust the Position Center adjustment VR203 ( CH1 , VR303 ( CH2 for a trace at the horizontal center line. 19 Cl71 Check/Adjust Xl AC GAIN.
35、: : e. Set the TIME/DIV switch to the 1mS position. Set the VOLTWDIV switch to the 10mV position. Set the AC-GND-DC switch to DC. Connect the square-wave generator( using 1KHz output range ). Adjust the output amplitude of that generator for 5 division deflection of screen. f.Check that the high-vol
36、tage level of pulse is flat. g. Adjust the X 1 AC GAIN adjustment VR202( CH1 ),VR302( CH2 ) for a flat level. Cl81 Check/Adjust Vertical Gain. a. Set the VOLTWDIV switch to the 10mV position and AC-GND-DC switch to DC. b. Connect the standard amplitude calibrator to the input Connector. c. Set the s
37、tandard amplitude calibrator for a 50mVp-p signal. d. Check for a display of five divisions. e. Adjust the GAIN adjustment VR204 ( CH1 ), VR304 ( CH2 ) for a display of 5 divisions within 3%. f. Check all the VOLTWDIV switch settings. Cl91 Check/Adjust Input Capacity ( ATT : +l ). a. Set the VOLTWDI
38、V switch to the 10mV position. b. Set the AC-GND-DC switch to DC. c. Connect the L-C meter to the input terminals. d. Check the input capacity for approximately 25pF. C203 Check/Adjust Vertical Step Response. E : C. d. e. Set the VOLTWDIV switch to the 10mV position. Set the TIME/DIV switch to the 0
39、.2s position. Connect the fast-rise, positive output ( 50mV, 1MHz ) of the square-wave generator to the input. Use a 500 termination and cable. Set the square-wave generator to 1MHz. Adjust the square-wave generator output for a 5 divisions display. CH1: Adjust the VC503 for a square-wave that is fl
40、at. Then, adjust VC501 for over-shoot that is +0.15DIV. CH2: Adjust the VC306 for over-shoot that is +0.15DIV. 20 Zl Check/Adjust Attenuation Compensation ( ATI G-0, Sl00 1. a. Set the AC-GND-DC switch to DC. b. Connect the square-wave generator to the CH1 ( CH2 ) input terminals, check for a square
41、-wave that is flat ( flat top ) under the following settings. ATTVOLTWDIVThe square-wave generator output + 100.1 v0.5 V t1001v5 v c. Adjust the trimmer condenser for a square-wave ( flat top 1 under the following settings. ATT I I VOLTWDIVThe square-waveAdjust generator outputCH1 (CH21 + 10 10.1 v
42、I 0.5 VVC204 ( VC304 1 Sl00 1 1 v 15 vVC203 ( VC303 II221 Check/Adjust Input Capacity. a. Connect the L-C meter to the input connector. b. Check the input capacity for a approximately 25pF. c. Adjust the trimmer condensers for a 25 pF input capacity under the following settings. I ATT1 VOLTWDIV 1Adj
43、ust CH1 ( CH2 I Sl I 5 mV I ( VC305 +10 I 0. 1 v I VC201 ( VC301 ) I t100 ) 1 v VC202 ( VC302 ) 21 - _-“.l_-l . ._-.- T R I G G E R I N G S Y S T E M C231 Check/Adjust TRIG CENT. a. Set the TRIG SOURCE switch to the CHl, the TRIG SLOPE knob pushed in, the VOLTWDIV switch to 10mV and the TIME/DIV swi
44、tch to the 20s. b. Connect the sine-wave generator to the input connector for a 0.3DIV ( 50KHz ). c. Set the TRIG LEVEL knob to the midposition. d. Adjust the VR605 so that synchronization is effected on the waveform, 0.3DIV on the screen. e. Next, set the TRIG SLOPE to -(pulled out state) and insur
45、e that synchronization is effected. After confirmation, leave the TRIG-SLOPE in the depressed state. Readjust when stepped out. C241 X-Y Operation 24-l Check/Adjust X Gain. a. Set the V-MODE switch to CHCheck horizontal, vertical Signal Generatormaximum frequency 70MHz ;and trigger bandwidth. Variab
46、le amplitude 2. Standard Amplitude Amplitude accuracy : 0.25% ,Check horizontal and CalibratorVariable amplitude ; 5mV toVertical gain. 40V ;frequency :1KHz square wave 3. Square - wave Generator Variable frequency : 10Hz toCheck probe and vertical 1MHz ;output amplitude :compensation. 10mV to 100V
47、4. Digital Multimeter 0.1% accuracyCheck power supply. 5. Digital Frequency0.1% accuracyCheck CAL frequency. and Counterfunction Generator frequency. 6. TimeMark Generator 0.1% accuracyCheck horizontal timing. 7. CableImpedance : 50s1 ; type :External trigger operation RG-58/U ; length : 42 inches ;
48、check. Horizontal gain check connectors : BNC.and adjustment. 8. TerminationImpedance : 50ti ;Vertical Amplifier compensati Connectors : BNC.-on checks and adjustment. 9. AttenutorRatio : 10X; connectors :Vertical Amplifier BNC ;impedance : 50S1bandwidth check. 10. T - ConnectorConnectors : BNC.External trigger operation checks. 11. DISTORTION FACTOR METER Function G
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