EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: fabry891 on December 26, 2024, 05:15:01 pm
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Hello everyone,
I have had a UNI-T UT61E digital multimeter for a few years now, which has always worked well for my hobby use.
Today I noticed that in continuity test mode if I put the two leads in contact, even with a low ohm value less than 1, I do not hear the beep, but I hear a quick beep only when I disconnect the leads. Also in DC voltage test mode, even without leads inserted, I have a value of about -0.3 V.
I also tried to power it with an external power supply, to exclude the battery problem, but the problem persists.
I wonder if anyone has already had the same problem as me and how to solve it.
Thanks.
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Using an external power supply is usually a bad idea.
Geting -0.3 V DC when open is a bad sign and likely not directly related to the continuity problem.
With a handheld DMM there is usually is low chance for a repair, as parts are hard to get and new calibration may be needed, that may be difficult (rarely the procedures are public) or expensive to get.
A possibly issue effecting multiple areas could be a damage from humidy or a leaking battery. If no longer under warranty, maybe have a look.
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That sounds bad.
What was the previous thing you did to it?
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Check your test leads/try another set.
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Check your test leads/try another set.
Bad leads won't subtract 0.3V DC from the input, especially when they aren't connected.
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That sounds bad.
What was the previous thing you did to it?
Nothing special, I always work with low voltage and low current. I don't know if it's my fault or the quality of the instrument.
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Check your test leads/try another set.
Tried another set of leads, same problem. Same leads on another meter work. Mystery. I think I'll just keep it that way at this point. Eventually I have another multimeter/oscilloscope for more precise measurements.
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Take it apart and clean the rotary contacts?
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Take it apart and clean the rotary contacts?
Turn the switch vigorously a dozen times. Push down on it, hard.
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post a pcb picture.
there are 2 variants - if i see which you have i can post a schematic.
it could be as simple as a shorted diode.
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post a pcb picture.
there are 2 variants - if i see which you have i can post a schematic.
it could be as simple as a shorted diode.
Following some forums I tried to remove the potentiometer VR1 (2k ohm, while in the circuit diagram it is indicated 1k ohm) and the DC value returned to almost zero, but obviously not from correct voltage readings, while always without the potentiometer, the continuity test works correctly. Does this mean something?
Here are the pictures of the pcb.
https://photos.app.goo.gl/QZ5J3MTrFgMMEqaJ6 (https://photos.app.goo.gl/QZ5J3MTrFgMMEqaJ6)
https://photos.app.goo.gl/HgmjpTX6Ghv68PAh7 (https://photos.app.goo.gl/HgmjpTX6Ghv68PAh7)
Circuit diagram:
https://photos.app.goo.gl/VvY5VaPfyc5fJD6C8 (https://photos.app.goo.gl/VvY5VaPfyc5fJD6C8)
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- Measure VR1
- Verify that the value is less than the total resistance
- Take note of the value
- Move a bit the cursor
- Verify a minimal resistance variation
- Move the cursor some times
- Replace the cursor at the previous resistace
- Reinstall VR1.