| Electronics > Repair |
| Please help, FLUKE 8920A Multimeter Repair |
| << < (24/45) > >> |
| Harry_22:
Good job! Look what happened this time. Previously we localized a fault in operational amplifier A assembled here using discrete elements. What it looks like. At the direct input we have 0V at the inverse 0.17V at the output 8.3V. (Gain factor was 50) There is a clear imbalance here. Now it has become clear that when you connect voltmeter probe to the inverse input oscillations occur. This despite the fact that the input is shunted with a feedback resistor 110 Ohms. At this rating there should be no interference! PS You can change all the capacitor of cause but are you sure that this will 100% solve the problem? |
| Harry_22:
Could you connect generator to the device input and check the signal on TP1. Adjust the amplitude to see a more сlean signal. |
| daisizhou:
Since there has been no progress for a long time, I don't know where to start to solve the problem,Replacing the capacitor is just my guess. If you have any other places you need tested, please let me know. thanks :) |
| daisizhou:
--- Quote from: Harry_22 on June 09, 2024, 11:12:08 am ---Could you connect generator to the device input and check the signal on TP1. Adjust the amplitude to see a more сlean signal. --- End quote --- I can connect a signal generator to the input.Could you please tell me the type of input signal or the specific voltage value, etc..... The output is TP1. Use an oscilloscope to view the waveform of TP1? Please tell me the specific test details |
| Harry_22:
Sinus 1kHz as usual. Gradually increase the amplitude until a good signal appears on the oscilloscope screen. Yes connect oscilloscope to TP1. |
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