JYE Tech Forum

DSO138 is a fantastic instrument. Highly recommended. Now I can spy on the serial communication on my Arduino projects.
Two comments though: The mark R38 is doubled up on the PCB. (This is not a problem if you have a look at the circuit diagram.)
I am not able to calibrate the probe. When I use the varicaps, I do not see any difference on the screen. Anyway the test signal looks fine to me, but corners are not perfect. Could the reason be that I have mixed one of the ceramic caps?

You have purchased a counterfeit DSO138 kit. Original DSO138 kits from JYE Tech do not have the duplicated R38 mistake.

If you mixed the caps you won't be able to do good compensation for probe. The caps have value marked so shouldn't be mixed.