leader_lbo-516_delayed_time-base_100_mhz_oscilloscope_calibration_and_maintenance 电路图.pdf

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RadioFans.CN 收音机爱 好者资料库 TABLE OF CONTENTS (Continued) 3-4 CALIBRATION OUTPUT ADJUSTMENT .30 3-5 A TIMEBASE ALIGNMENT .30 3-5-1 Slow Sweep Time .30 3-5-2 Sweep Length .30 3-5-3 Fast Sweep Time .30 3-5-4 Sweep Start Point .30 3-5-5 Timebase Accuracy Check .30 3-6 A TIMEBASE X10 MAGNIFIER ADJUSTMENT .30 3-6-1 Magnifier Positioning .30 3-6-2 Magnifier Speed Accuracy .30 3-7 B TIMEBASE ALIGNMENT .30 3-7-1 Slow Sweep Time .30 3-7-2 Length Adjustment .31 3-7-3 Sweep Start Point .31 3-7-4 Fast Sweep Time .31 3-7-5 Timebase Accuracy Check .31 3-7-6 Start Points Alignment .31 3-8 VERTICAL AMPLIFIERS .31 3-8-1 DC Balance Adjustment .31 3-8-2 Attenuator Step Balance .30 3-8-3 X1 AC Gain Compensation .31 3-8-4 X10 AC Gain Compensation .31 3-8-5 Gain Calibration .31 3-8-6 CH-2 Invert Balance Adjustment .32 3-8-7 CH-1/CH-2 Input Capacitance Adjustment .32 3-8-8 CH-1/CH-2 Input Attenuator Compensation .32 3-8-9 CH-3 Direct Input Capacitance Adjustment .32 3-8-10 CH-3 Attenuator Compensation .32 3-8-11 CH-3 Attenuator Input Capacitance Adjustment .32 3-8-12 CH-3 Gain Adjustment .32 3-8-13 CH-1 Output Level Adjustment .32 3-8-14 CH-1/CH-2 HF Pulse Response Alignment .32 3-8-15 CH-1/CH-2 Frequency Response Check .33 3-8-16 CH-1 Output Pulse Response .33 3-8-17 CH-1/CH-2 X10 Magnifier Bandwidth Check .33 3-8-18 Vertical Position Control Centering .33 3-8-19 ADD Balance Adjustment .33 3-9 TRIGGER CIRCUITRY ADJUSTMENTS .33 3-9-1 Trigger Balance and Centering Alignments .33 3-9-2 Trigger Balance Adjustments for Multitrace Modes .33 3-9-3 Preset Trigger Adjustment .34 3-9-4 CH-3 Pulse Response Adjustment .34 3-9-5 Internal Trigger-Pulse Response Adjustment .34 3-10 X-Y MODE ADJUSTMENTS .34 3-10-1 Gain Adjustment .34 3-10-2 Balance Adjustment .34 4. REPLACEMENT PARTS LIST 37 5. BLOCK DIAGRAM, SCHEMATICS AND P.C. BOARDS 51 3. MAINTENANCE AND CALIBRATION 3-0. The following test equipment is required to perform the calibration/maintenance procedures described in this section. The performance specifications given are the minimum necessary to accurately calibrate the oscilloscope. Description Minimum Specifications 1. Digital Voltmeter DC Voltage Range: 0-200 VDC Accuracy: +0.5% 2. High Voltage DC Voltage Range: 0-2000 VDC Voltmeter Accuracy: -+ 1% 3. Frequency Counter Frequency Range: 100 Hz - 200 MHz Overall Accuracy: +0.001% 4. Time Mark Generator Marker Outputs: 2nS - 0.5 S with calibrated + 5% offset adjust Accuracy: -+0.1% 5. Sine Wave Generator Frequency Range: lkHz - 200 kHz Output Level: 15 mV - 5 Vp.p Accuracy: -+.3 dB, 1 MHz - 200 MHz as frequency is changed 6. Test Oscilloscope 100 MHz Bandwidth 7. Square Wave Frequency: 1 kHz - 100kHz, -+1% Generator Output Level: I mV - 1.0 Vp-p, -+1% Rise Time: 3 nS 8. Amplitude Calibrator Output: 1 kHz square wave Frequency Accuracy: -+0.25% Output Level: 2 mV - 20 Vp-p 9. Capacitance Meter Range: 0-50 pF Accuracy: - 1% 3-1. INITIAL SETUP CONDITIONS POWER switch .Pushed in A INTEN control . Centered* B INTEN control . Centered* ILLUM control . Clockwise FOCUS control . Centered* AC/GND/DC switches . DC VOLTS/DIV switches . 20mV VARIABLE controls . Clockwise X10 MAG switches Pushed in Vertical POSITION controls . Centered*. PULL QUAD control . Pushed in PULL TRIPLE control . Pushed in V MODE switches . CH-1 CH-2 INV switch . Out DLY TIME MULT control . Counterclockwise. COUPLING switch . AC SOURCE switch .CH-1 LEVEL control . 0 HOLDOFF control . Detented counter clockwise and pulled out A/B TRACE SEP control . Centered SLOPE switch . Out HORIZ DISPLAY switches. . A START switch . Out SWEEP MODE switches . AUTO A TIME/DIV switch . .5 mS B TIME/DIV switch . .1 mS A VARIABLE control . Clockwise Horizontal POSITION control . Centered* * Adjusted afterwards for best viewing. Allow 30 minutes warmup before making any adjust- ments. Remove the top and bottom covers to gain access to test points and internal adjustments. 3-2 POWER SUPPLY CHECK AND ADJUSTMENT 3-2-1 -8 Volt Adjustment Connect a digital voltmeter s positive lead to the scope chassis (GND), and the voltmeter s negative lead to TP-5 lo- cated on PCB T-3153. Adjust VR-1 for -8.0 V. 3-2-2 Power Supply Check Check the voltages listed below by moving the voltmeter s negative lead to chassis ground, and applying the positive lead, in turn, to each of the associated test points on PCB T-3153. Nominal Test Point Voltage Tolerance TP-I +100 +98 VDC to 102VDC TP-2 + 50 49 51 TP-3 + 12 11.75 12.25 TP-4 + 8 7.85 8.15 TP-6 + 5 4.8 5.2 TP-7 + 19 17.5 20.5 3-2-3 High-Voltage Adjustment Turn off the unit under test. Connect the positive lead of a HV voltmeter to chassis ground, and its negative lead to TP-8. Turn the scope on and allow a 2 minute warmup. Adjust VR-2 on PCB T-3162 for a reading of - 1950 volts. Connect an X10 probe to the test oscilloscope and hold its tip close to the face of the CRT under test. The high-voltage ripple displayed on the test oscilloscope should be less than 0.1Vp-p. 3-3. CRT CONTROL ADJUSTMENTS Make sure the controls are set according to the initial setup conditions in Paragraph 3-1 before starting the following adjustments. 3-3-1 Intensity Range Adjustment. Center the CH- 1 trace on the CRT with the vertical POSITION control. Set the A INTEN control knob mark to an approximate 45 angle as shown in Figure 3-1. Adjust VR-I on PCB T-3162 until the trace becomes just barely visible. 3-3-2 Astigmatism Adjustment Connect a sine wave generator to the CH-1 input connec- tor. Set generator frequency and output to produce five or six sine waves. Set output level and POSITION controls for a centered display 6 cm high. (Peaks of the sine waves just touching the graticule lines I cm above and below the bottom and topmost graticule lines.) Adjust A INTENS and FOCUS for a medium-bright, sharp display. Adjust VR- 1 on PCB T- 3157 for optimum overall sharpness. 29 3-4. CALIBRATION OUTPUT ADJUSTMENT Connect the test oscilloscope to the CAL connector on the fron panel of the LBO-516. Adjust VR-1 on PCB T-3287 for a CAL output level of 0.5 Vp-p +-1%. The duty cycle of the square wave should be 45-55%. Connect the CAL output to a frequency counter; the fre- quency should be 1000 Hz + - 10%. 3-5. A TIMEBASE ALIGNMENT 3.5-1 Slow Sweep Time Return the oscilloscope to the initial setup conditions. (See Paragraph 3-1). Adjust the time-mark generator for an output of .5 mS and connect it to the CH-1 input connector. Using the horizontal POSITION control, align the first mark with the leftmost vertical graticule line. Adjust VR-22 on PCB T-3158 to align each subsequent mark with a major vertical graticule line. 3.5-2 Sweep Length With the same conditions as in the previous paragraph, adjust the horizontal POSITION control to align the third mark with the leftmost vertical graticule line. (See Figure 3-2.) Adjust VR-1 on PCB T-3158 so the 13th mark is fully dis- played on the CRT screen. 3.5-3 Fast Sweep Time Return the oscilloscope to the initial setup conditions. (See Paragraph 3-1). Set the A TIME/DIV switch to 0.5 PS. Set the time-mark generator to 0.5/.PS and connect it to the CH- 1 input connector. Using the horizontal POSITION control, align the first mark with the leftmost vertical graticule line. (See Figure 3-2.) Adjust VC-22 on PCB T-3158 to align each subsequent mark with a major vertical graticule line. 3.5-4 Sweep Start Point Return the oscilloscope to the initial setup conditions. (See Paragraph 3-1). Set the A TIME/DIV switch to 0.1 mS. With the horizontal POSITION control, adjust the trace startpoint to the first minor division (0,2 major division). Change the A T1ME/DIV switch to 50/aS and adjust VC-1 on PCB T-3158 so the sweep starts at the leftmost vertical graticule line. 3.5-5 Timebase Accuracy Check Return the oscilloscope to the initial setup conditions. (See Paragraph 3-1). Set the A TIME/DIV switch to 0.5 S. Set the time-mark generator to 0.5 S and connect it to the CH- 1 input connector. Align the first mark with the left-most vertical graticule line. Adjust the generator so that each subsequent mark is aligned with a major vertical graticule line. Repeat for each A TIME/DIV switch setting from.2 S to 0.2PS, verify