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1. No Light Spot or Waveform
Power is not connected.
The brightness knob is not adjusted properly.
X, Y-axis offset knob is misaligned.
The Y-axis balance potentiometer is improperly adjusted, causing severe imbalance in the DC amplification circuit.
2. Horizontal Direction Cannot Expand
The trigger source selection switch is set to external, and there is no external trigger signal input, so no sawtooth wave is produced.
The level knob is improperly adjusted.
The stability potentiometer is not adjusted to keep the scanning circuit in a state ready to trigger.
The X-axis selection is mistakenly set to external, and there is no signal input at the external socket.
If a dual-trace oscilloscope only uses channel A (with no input signal on channel B), and the internal trigger switch is set to pull YB, then no sawtooth wave is produced.
3. No Display in Vertical Direction
The input coupling switch DC-ground-AC is mistakenly set to ground.
The high and low potential ends of the input are reversed with those of the measured circuit.
The input signal is too weak, while V/div is mistakenly set to a low sensitivity range.
4. Unstable Waveform
The stability potentiometer is excessively rotated clockwise, causing the scanning circuit to be in a self-excited scanning state (not in a state ready to trigger).
The trigger coupling mode AC, AC (H), DC switch cannot be correctly selected according to the frequency of the different trigger signals.
When selecting a high-frequency trigger state, the trigger source selection switch is mistakenly set to external (it should be set to internal).
Some oscilloscopes in automatic mode (continuous scanning) have unstable waveforms.
5. Dense Vertical Lines or Rectangular Display
The t/div switch is improperly selected, causing f scan << f signal.
6. Dense Horizontal Lines or Inclined Horizontal Line
The t/div switch is improperly selected, causing f scan >> f signal.
7. Inaccurate Voltage Reading in Vertical Direction
The vertical sensitivity (v/div) has not been calibrated.
During v/div calibration, the v/div fine-tuning knob is not set to the calibration position (i.e., not fully rotated clockwise).
During testing, the v/div fine-tuning knob is moved away from the calibration position (i.e., moved away from the fully clockwise position).
When using a 10:1 attenuation probe, the voltage is not multiplied by 10 during calculation.
If the frequency of the measured signal exceeds the oscilloscope’s maximum operating frequency, the oscilloscope reading will be lower than the actual value.
The measured value is peak-to-peak, while the effective value of the sine wave needs to be converted.
8. Inaccurate Reading in Horizontal Direction
The horizontal sensitivity (t/div) has not been calibrated.
During t/div calibration, the t/div fine-tuning knob is not set to the calibration position (i.e., not fully rotated clockwise).
During testing, the t/div fine-tuning knob is moved away from the calibration position (i.e., moved away from the fully clockwise position).
When the scanning speed expansion switch is set to pull (×10), the test is not adjusted according to the t/div switch indicator to increase sensitivity by 10 times.
9. Unclear DC Voltage Value of AC and DC Combined Signal
The Y-axis input coupling switch DC-ground-AC is mistakenly set to AC (it should be set to DC).
Before testing, the DC-ground-AC switch was not set to the grounding position for DC level reference point calibration.
The Y-axis balance potentiometer is not properly adjusted.
10. Cannot Measure Phase Difference Between Two Signals
Cannot measure the phase difference between two signals (waveform display method)
The dual-trace oscilloscope mistakenly sets the internal trigger (pull YB) switch to the normal position; it should be set to pull YB.
The dual-trace oscilloscope has not correctly selected the alternating and discontinuous mode for the display mode switch.
The single-trace oscilloscope trigger selection switch is mistakenly set to internal.
Even if the single-trace oscilloscope trigger selection switch is set to external, the two external triggers do not use the same signal.
11. Abnormal Amplitude Modulation Waveform
The t/div switch is improperly selected, and the scanning frequency is mistakenly selected according to the amplitude modulation wave carrier frequency (it should be selected according to the audio amplitude modulation signal frequency).
12. Waveform Cannot Be Adjusted to Required Start Time and Position
The stability potentiometer is not adjusted to the critical trigger point.
The trigger polarity (+, -) does not match the trigger level (+, -).
The trigger mode switch is mistakenly set to automatic (it should be set to normal).
13. Trigger or Synchronization Scanning
Slowly adjust the trigger level (or synchronization) knob, and a stable waveform appears on the screen. Adjust the level knob appropriately to display the waveform at the corresponding starting position as needed.
If using a dual-trace oscilloscope to observe the waveform, set the display mode switch to YA or YB for single-trace display. The measured signal is input to the oscilloscope through the YA or YB input terminal. The trigger source selection for the Y-axis is set to “internal trigger-pull YB” switch in the normal position.
If the oscilloscope is set for dual-trace display, set the display mode switch to alternating mode (suitable for observing signals with not too low frequency) or discontinuous mode (suitable for observing signals with not too high frequency); at this time, the trigger source selection for the Y-axis is set to “internal trigger-pull YB” switch in the pull YB position.
14. Abnormal Phenomena Caused by Improper Use
During the use of the oscilloscope, operators often encounter abnormal phenomena due to a lack of understanding of the oscilloscope principles and unfamiliarity with the functions of the oscilloscope panel controls, leading to improper adjustments.
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