UNI-T ut139c multimeter, broken, some functions stopped working

[rspt1908]

Good day everyone,

I had this meter for just short of a year now. I occasionally test each functions every month but I have never really used it yet in testing circuits as most of my projects then mostly involved programming or simultations. However, just today, I was trying to check the continuity of the cables and it just started beeping randomly even when the output is not shorted (multimeter is in continuity mode). I tried to check the other functions and confirmed that the Continuity Tester, Resistance Measurement, Temperature measurement and AC Voltage measurement no longer function properly. It just killed itself, I haven't even got to use it. ( I have only confirmed DC Voltage measurement as well as the NCV to be the only functions still properly working.

Video: https://youtu.be/nqIXN1PcZG4

I tried to check the innards and saw some shavings near the rotary switch however removing them didn't solve the problem, I didn't find any solder blobs causing shorts on the PCB (.

Does anyone have any ideas about this? I tried to look for the schematic online but could only find ones for the ut61e. Before purchasing, I read in some forums that turning on the meter while pressing some buttons may boot the meter in calibration mode and is sometimes enough to mess with the firmware on the eeprom. I have been careful to avoid this.

I couldn't sleep so I tried to build jumper connectors for my power supply to distract myself to avail. I couldn't send it for repairs as I bought it from the US and I live in the Philippines. I have a project coming up for our coursework and I need to measure temperature to confirm the functionality of our project. It took me a while to save money for this meter and would like to try to fix it. I wouldn't want to throw this in the bin since it was barely used

Pictures:
1. Rotary switch shavings, Front PCB

2. Back PCB 1

3. Back PCB 2

4. Back PCB 3

Here are some people dealing with similar issues:

1. UT139C sudden Brick after power on.no damage at all


2. UNI-T UT139C: DO NOT WORK AUTO RANGE

[hli]

First thing to check: put new, known-good batteries in.

[rspt1908]

Yup, I tried replacing the batteries but still yielded the same result   I used panasonic batteries

[stj]

clean the switch contacts and tracks with IPA or alcahol.
dirty contacts will cause problems like that.

[rspt1908]

Yup, I tried to clean the rotary contacts to no avail. I found some plastic shavings as indicated in the picture