BK 1477 Service Manual 电路图.pdf

jrfo Bi(F#C!S#J , SERVICE MANUAL 1472C 1477 lSMHz Triggered Sweep DUAL-TRAGE OSqLLOSCOPE lllronn Bt( , RadioFans.CN 收音机爱 好者资料库 WARilI1G fhis service mantrcrl is intended for use W qnlified electronics teclnicions only. To arrcid electnc shock, do not perf orm servrcrng urless yvu are qnlified to do so. High voltage up to 2000 rfDC is present on the CRT and power supply board when tJle oscilloscope is operating. High voltage up to f95 VDC is present on the sweep board. Line voltage of LZO VAC (or 240 VAC) is present on the power transformer, on-off switch, and power supply board any time the oscilloscope is corurected to:ur AC power source, even if turned off. Always observe caution when the housing is removed from the unit. Contacting exposed high voltage could result in fatal electric shock. - DIFFERENCE-S BETWEEN MODELS This second edition of the service manual is expanded to include Model t477. Electricaly, Model 1477 is very similar to the Model 1472C. A sep- arate schematic is supplied for eadr model. The circuit board drawings essentially apply to both models. Model L477 has several changes in ap- pearzrnce from Model l47ZC, using a new front panel, new handle, new knobs, etc. A parts list itemizing those parts which are unique for Model 1477 is on page 34. - RadioFans.CN 收音机爱 好者资料库 b TABLE OF CONTENTS OPERATORS CONTROLS INDICATORS AND FACILITIES . . . . . . . . . . 3 S P E C I F I C A T I O N S . . . . . . . . . . . . . . o . . . . . . . . . . . . . o o . . . . . . . . . . . 5 C I R C U I T D E S C R I P T I O N . . . . . . . . . . . . . . . . . f . . . . . o . . . . . . . . . . . . 7 S E R V I C I N G . . . . . . . . . . . r . . . . . . . . . . o . . . . . . . . . . . . . . . o o . . . . . 8 TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 AD JU STM ENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 P A R T S L f S T . . . . . . . . . . . . . . . . . . . . . . . . o . o . . . . . . . r r I r . . . . . , Z ! CIRCUIT BOARD MAPS P o w e r S u p p I y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 7 V e r t i c a l A m p l i f i e r . r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8 S w e e p B o a r d . . . . . . . . . . . . . . o o . . . . . . . . o . o . o o o . . r . . . . . 2 g VO LTAGE M EASUREM ENTS . . o . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 MODEL I4TZCPRODUCTION CHANGES. . . . . . . o . . o . . . . . . . . . . . . 30 M O D E L I 4 7 Z C S C H E M A T I C D I A G R A M S . . . . . . . . . . O I 3 1 M O D E L 1 4 7 7 P A R T S L I S T . . . . . . . . . . . . . . . . o . . I r . . . o . . . . o o . . 3 4 MODEL 1477 SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . 35 M O D E L 1 4 7 7 P R O D U C T I O N C H A N G E S . . . . . . o . . . o . . . . . . . o o o . . . . 3 7 REERENCE PUBLICATION S I47ZC Instructiorr Mantral . . . . . . o . . . . . . . . . . o . . . . . . . 480-1.82-9-001 L47ZC Composite (Schematic Diagram normal when pushed in. 9. TRIGGERING TEVEL control. Sync level adjustment determines points on waveform slope where sweep starts; (-) equals most negative point of triggering and (+) equals most positive point of triggering. Push-pull switch selects automatic triggering when pulled out (PULL AUTO). When automatic triggering,-a sweep is generated even without an input signal. 10. EXT TRIG jack. Input terminals for external trigger signal. ll. SYNC switch. Four-position lever switch with the following positions: SI-oPE. The SLOPE positions are used for viewing all waveforms except television composite video signals. (+) lweep is triggered on positive-going slope of waveform. (-) Sweep is triggered on negative-going slope of waveform. TV. In the TV positions, the sync pulses of a television composite video signal are used to trigger the sweep; the vertical sync pulses (frame) -are automatically selected for sweep times of 0.5 SEC/cm to 0.1 mSEC/cm, and horizontal sync pulses (line) are automatically selected for sweep times of 50 gSEC/cm to .5 pSEC/cm. (+) Sweep is triggered on positive-going sync pulse. (-) Sweep is triggered on negative-going sync pulse. 12. SOURCE switch. Tfuee-position lever switch selects triggering source for the sweep. Both sweeps are triggered by the same source in dual trace operation. CH A Sweep is triggered by Channel A signal. CH B Sweep is triggered by Channel B signal. EXT Sweep is triggered by an external signal applied at the EXT SYNC jack 10. 13. Channel B POSITION control. Vertical position adjust- ment for Channel B trace. Becomes horizontal posiiion adjustment when SWEEP TIME/CM switch 5 ii in the CH B position. 14. Channel B DC BAL adjustment. Vertical DC balance adjustment for Channel B trace. 15. Channel B INPUT Jack. Vertical input jack of Channel B. Jack becomes external horizontal input when SWEEP TIME/CM switch 5 is in the CH B position. 16 Channel B DC-GNDAC switch DC Direct input of AC and DC component of input signal. GND Opens signal path and grounds input to vertical amplifier. This provides a zero-signal base line, the position of which can be used as a reference when performing DC measurements. AC Blocks DC component of input sigid. 17. Channel B VOLTS/CM switch. Vertical attenuator for Channel B which provides step adjustment of vertical sensitivity. Vertical sensitivity is calibrated in I I steps from .01 to 20 volts per crnwhen VARIABLE contrbl l8 is set to CAL position. This control adjusts horizontal sensitivity when the SWEEP TIMETCM switch 5 is in the CH B position. 18. Channel B VARIABLE control. Vertical attenuator adjustment provides fine control of vertical sensiviti$. -i In the extreme clockwise (CAL) position, the verticd attenuator is calibrated. This control becomes the line horizontal gain control when the SWEEP TIME/CM switch 5 is in the CH B position. 19. MODE switch. Five-position lever switch; selects the basic operating modes of the oscilloscope. CH A Only the input signd to Channel A is displayed as a single trace. CH B Only the input signd to Channel B is displayed as a single trace. A both the Channel A and Channel B inpu.t signds are displayed on two separate traces. A + B The waveforms from Channel A and Channel B inputs are added and the sum is displayed as a single trace. A- B The waveform from Channel B is subtracted from the Channel A waveform and thc difference is displayed as a single trace. If only a Channel B input is present, the display is inverted. 20. Channel A VOLTS/CU switch. Vertical attenuator for channel A which provides coarse adjustment of vertical sensitivity. vertical sensitivity is calibrated in I I steps - OPERATORS CONTROI.S. INDICATORS AND FACILITIES 21. 22. 23. 25. from .01 to 20 volts per cm when VARIABLE control 2l is set to the CAL position. Channel A YARIABLE control. Vertical attenuator adjustment provides fine control of vertical sensitivity. In the extreme clockwise (CAL) position, the vertical attenuator is calibrated. Channel A DC-GNIIAC switch. DC Direct input of AC and DC component of input signal. GND Opens signal path and ground input to vertical amplifier. This provides a zero-signal base line, the position of which can be used as a reference when performing DC measure- ments. AC Blocks DC component of input signal. Channel A INPUT jack. Vertical input jack of Channel A. Channel A DC BAL adjustment. Vertical DC balance adjustment for Channel A trace. Channel A POSITION control. Vertical position adjust- ment for Channel A trace. 26. ASTIG adjustment. Astigmatism adjustment provides optimum spot roundness when used in conjunction with the FOCUS control 27 and INTENSITY control 28. Very little readjustment of this control is required after initial adjustment. 27. FOCUS control. 28. INTENSITY control. Adjusts brightness of trace. 29. Fuse holder. 30. AC line cord. CSA-approved for oscilloscopes. 31. INT MOD jack. Intensity modulation (Z-axis) input. 32. Combination carrying handle and tilt stand. 33. Probe (see Fig. 3). The B trace auto matically chopped at all sweep times of I mS/cm and slower; alte rnate trace automaticallv selected for all faster sweep timei. A + B (single-trace algebraic sum of Channels A and B). A - B (single-trace algebraic dif- ference of Channels A and B). 200 kHz (n0%) Better than 60 dB. Triggered and automatic. In auto- matic mode, sweep is obtained without input signd. 0.SpSEC/cm to 0.5 SEC/cm (!57) in 19 ranges, in l-2-5 se- quence. Each overlapping range provides for fine adjustment. At least 2.5 times. Obtained by enlarging the above sweep 5 times from center. Maxi mum swee p speed becomes 0.1,/SEC/cm. 3% or less distortion for 0.5 SEC/cm to 2 pSEC/cm ranges. 5% or less for I pSEClcm and 0.5 pSEC/cm ranges. 102 mm to I l0 mm. CH A, CH B and EXT: I V p-p sensitivity. P ositivc and negative, con- tinuously variable level control; pull for AUTO. 2O Hz to 15 MHz (min. 0.5 cm deflection as measured on cathode ray tube). Input Regulatron MISCELLANEOUS Scale Mechanical Features PROBES Model No. Attenuation Input Impedances Connector Tip l0 mV/cm (nominal). DC to I MHz (-3 dB). I megohm (nominal). 22 pF (t3pF). 300 V (DC + AC peak) or 600 V pp. With SWEEP TIME/CM switch in CH B position, the CH A input becomes the Y input (vertical) and the CH B input becomes the X input (horizontal). The CH B position control becomes the horizontal position control. 120 VAC, 50/60 tlz,23 watts. (3-wire line cord, CSA-approved for oscilloscopes.) 108 to 132 vAc. Variable illumination. Carrying handle for tilt stand. PR-35 (two required). Combination l0:l and direct. l0:l = l0 megohms, l8 pF. Direct = I megohm, 120 pF. BNC Spring-loaded hook-on tip. SWEEP CIRCLJITS (Common to CH A and CH B) CALIBRATION VOLTAGE I kHz square wave of I V p-p (!s%). INTENSITY MODULATION v v v. q) (J .tt () (n q) O F e.l r- :v q) oo cO E .Y() c/) Eb TI J F l - u J z ) i . | c = i F . J a o o( ? c r- trJ J 5ee_, a ; ; JC c ( a1 UJ Ycr - 0 - Y t z a < U J o jd. =qH ( F l =gt ( I F r! lrr F z tr- O tJ.F o.r| o 6 J Z o ( I A F f . z ) lJ. 11n FM rr,l - O c ( O u - 5 4 ( J o Ug ( O r * 2. ias J A IJ(J J a O trJ C r ! F z o o (J 9 o H a;H ? 2 - = o - F 35; 2 a lrJ O a z a < FI vl F F U J E-l 5e a <!lo 5:r m)lo. v < - T ( G ;i: d ir - t t c J :i ICr o(L s! - F - !d (f; 5r F uz- 3 o iz ( ( r ? o i eki ;ll u l F |, 3r E! y1 ;i 3r Eq ,r7, O F Ik s trJ J o ? c Y J B U 1 z I X F (a T Z o - j 6 b CIRCUIT DESCRIPTION : U The block diagram, Fig. 3, outlines the circuit break- down of the oscilloscope. Circuit details are obtained by reference to the schematic diaeram. GENERAL Basically. the oscilloscope consists of two identical vertical preamplifiers, each having its own input attenuator network. The outputs of the vertical preamplifiers can be switched, as desired, into the main vertical amplifier. The type of switching of the CH A and CH B preamglifiers is determined by the position of the MODE switch and MODE of OPERATION LOGIC. The main vertical arnplifier feeds the VERTICAL OUTPUT AMPLIFIER, which drives the vertical deflection plates of the CRT. Horizontal deflection is provided by the horizontal amplifier. Drive to the horizontal amplifier is furnished by calibrated sweep speed circuits or by the signal from the CH B preamplifier when X-Y operation is selected. All supply voltages are fully regulated and a DC-to-DC converter provides a regulated 2kV accelerating potential to the CRT. VERTICAL PREAMPLIFIERS Channel A and Channel B preamplifiers contain identical circuitry and circuit operation is the same for both. The vertical attenuator has two sections. The first section of the attenuator provides ratios of l: l, l0: l, 100: l, 1000: l. The second section provides ratios of 2: I and 5: l. The combined effect of the two sections is to provide the vertical attenuator ratios in a l-2-5 sequence. The vertical preamplifier consists of FET input tran- sistors Ql02 and Ql03 and transistors Ql04 thru Q109. FETs Ql02 and Ql03 form a balanced differential amplifier pair with output signals of opposite polarity. VRl0l is the front panel DC balance control and VRll2 an internal balance control. The output of Q 102 and Q 103 is applied to emitter followers Q 104 and Q 105 which lower the output impedance to drive conventional amplifier stage Ql06 and Q107. VRl05 and VRl06 are balance pots for the I 12 and I /5 attenuator positions. The VARIABLE control adjusts the gain of Ql06 and Ql07 while VRl0l provides a DC component to move the trace vertically across the screen. Amplifier gain is adjusted by VRl07 in the emitter circuit of Ql08 and Ql09 to provide the correct deflection factor for accurate voltage measure- ments. The trigger amplifier Q I l9 and Q I 20 amplifies the signal a the emitter of Q 108 and Q 109 and provides a portion of tne signal to the trigger circuits. The only difference between CH A and CH B pre- amplifiers is that the MODE switch reverses the polarity of the CH B signal when in the A-B position. MODE LOGIC The mode of operation (CH A, CH B, A , rPlot Tpt02 ATTENUATOR iitr;9,. DC BAL ADJ. $*, VRl06 _grclol (h rrcl03 1 riros 100 10 1 * TC104 TCIO2 TC106 I - FRONT PANEL (SACK VIEW) v 3. 4. Set VOLTS/DlV to 0.1V and adjust the trrmmer TC 1O2 (TC108 for CHB) on the lower printed circuit board so that optirnum square wave can be obtained. Adjust the trimrners TC104 arrd TC106 (TC110 arrd TC112 tor CHB) in the 1V arrd 10V ranges in the same rnanner. VERTICAL SENSITIVITY ADJUSTMENT 1. Remove the case according to the procedures describ- ed for REMOVING THE CASE. 2. Set VOLTS/DlV to 0.01V and turn VARIABLE fully clockwise to CAL. 3. Apply 0.05V p-p square wave signal to the vertical r nput. 4. Adjust VR107 GAIN ADJ (VRl10 GAIN ADJ for CHB) on the lower printed circuit board to obtain 5 div of vertical amplitude. ADJUSTMEITS Rear Printed Circuit Board Power Supply) CRT CENTERING ADJUSTMENT 1. Short the test terminals TP101 and TPlO2 on the lower printed circuit board. 2. With a horizontal bright line displayed in CRT, adjust VR114 on the same printed circuit board until the bright lirre is centered. FREOUENCY CHARACTERISTICS AND OVERSHOOT ADJUSTMENT 1. Apply a 100 kHz square wave signal having a good rise characteristic to the input. 2. Adjust the middle range of the square wave (after ris- ing) with TC301 on the rear printed circuit board. 3. Adjust the high range of the square wave (rising por- tion) with VR305 on the same printed circuit board. 4. Adjust the high range for each channel; for CHA with TC113 on the lower printed circuit board, and for CHB with TCl14. - It POWER SUPPLY BOARD ROTATE PLUG TO CHANGE VOLTAGE 240 VAC I 20 VAC FUSE O 7A_ 1 20 VAC o 34-240 vAC TOP VIEW TC TC VR VR VR VR VR 3 0 1 - M I D F R E O U E N C Y 3O2-UNBLANK 3 O 5 - H I G H F R E O U E N C Y 3 0 6 - r 9 k v A D J 3O7 _ INTENSITY ADJ 3O8-Y DEFLECTION 309- 1 95V ADJ VR 3O5 Fis