Found: Cut Trace in DSO150

How should I fix this?

I have had a clone of JYE Tech DSO150 / DSO Shell oscilloscope for two weeks now. Being my first oscilloscope, I bought it without knowing what to expect. Before this I have never even handled an oscilloscope, toy or not. All I know about this oscilloscope is from what I watched on YouTube and online reviews. Hackaday reviewed this cheap scope back in 2017.

This evening when I was probing around when the scope stops showing waveforms, so I tried probing the test signal. The 1kHz test signal is gone. Both the 3.3V and 0.1V test signal is gone. I changed the couping to GND, to DC, to AC, replugged the probe to the BNC connector, rebooted the scope … nope, its gone alright.

So I opened it and started looking around, and look what I found on the analog board:

A cut/lifted copper trace on the analog board.

I don’t know how long that cut trace has been there. There doesn’t appear to be any burn marks near it, so probably not because of too much current. The solder mask covering the trace is gone as well. I am guessing both the solder mask disappearance and the cut copper trace is the result of the analog board being hit or scratched by someting. No idea how. The test signal works fine when I just received the scope, though.

To fix the cut trace, I don’t think I can just bridge them by soldering. The remaining solder mask around the area will make bridging the copper traces very difficult. I happen to have a roll of copper tape, so I’ll use that to bridge the cut, and then solder them.

First, I straightened the remaining copper traces:

Straightened. Now you can see the actual missing length of the copper trace.

I cut a strip of copper from the copper tape. Just a small strip.

This is the copper tape, I just need to cut a small strip.
See that small copper strip near the cut trace. That’s probably too much already.
Applied the copper strip on top of the cut copper trace. Press it to make sure they make contact. I tested continuity using a multimeter and they seem to be connected already.
The strip and the traces are bridged by soldering them. I tested continuity again to make sure they are connected.

Before putting it back together again, I booted it to see if the test signal is detected again, and it is! So I put everything back together (definitely more difficult than opening it), and tried it again.

It works! The 3.3V and 0.1V 1kHz test signal appears again.

One problem solved! Now I can continue my probings šŸ¤­. By “now” I mean tomorrow of course.

Also, its not visible in these photos, but the main board has a STM32F103C8T6 chip. No idea if it is genuine.