| Electronics > Repair |
| Please help, FLUKE 8920A Multimeter Repair |
| << < (16/45) > >> |
| daisizhou:
Dear Harry_22. When I press the "LOW RANGE ENABLE" button, the flashing occurs again. :palm: Please see the video I took |
| Harry_22:
Hello again! These are the unpleasant consequences of repairs when you give equipment to the customer and he returns it again. Therefore you should always find the actual cause of the malfunction and not clean the connectors or replace all the capacitors first. Let's continue. Push "LO RANGE ENABLE" button. Check that TP1 voltage is around 8.6V Measure DC voltage at R18, R27, R30, R35, R40, R41 R42 and C24. You will get two values for each component. It doesn't matter which side is where. |
| daisizhou:
Hi Harry_22. Normally, the upper shield cover is closed,Press the "LOW RANGE ENABLE" button, the 2Mhz MAX indicator will light up. If I test TP1, only the upper shield cover can be opened,Then when I press the "LOW RANGE ENABLE" button, the 2Mhz MAX indicator does not light up,Looks like the "LOW RANGE ENABLE" feature is gone,It may be caused by too much interference,The GND connection line is also connected normally. In other words, if the upper shielding shell is opened to measure "LOW RANGE ENABLE", it will not be possible, so how should I measure it? |
| daisizhou:
--- Quote from: Harry_22 on May 22, 2024, 12:49:25 pm ---Hello again! These are the unpleasant consequences of repairs when you give equipment to the customer and he returns it again. Therefore you should always find the actual cause of the malfunction and not clean the connectors or replace all the capacitors first. Let's continue. Push "LO RANGE ENABLE" button. Check that TP1 voltage is around 8.6V Measure DC voltage at R18, R27, R30, R35, R40, R41 R42 and C24. You will get two values for each component. It doesn't matter which side is where. --- End quote --- Once again I tested the above test points as you requested, but unfortunately the fault disappeared as soon as I opened the upper shield cover.To be precise, when I opened the upper shield cover, the "LOW RANGE ENABLE" function disappeared and the "2Mhz MAX" indicator light went out. How do I test next? |
| Harry_22:
The most sensitive range up to 2mV is turned on only when the Low Range Enable button is pressed and the Auto Range button is not pressed. 2MHz LED is lit when this range up to 2mV is active. If the signal is more than 2mV then the range automatically switches to a higher one and 2MHz LED goes out. When the cover is opened the noise increases and the lower range no longer turns on. Use an oscilloscope to see what is happening at TP1. |
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