I bought a DSO 138 kit and soldered it together, but when it gets power, unfortunately, I only see a white screen. The green LED blinks with about a 1-second period, and nothing else happens; pressing the reset button only restarts the LED blinking. I'm thinking it might be constantly restarting the entire circuit for some reason.

The power supply is a stable 9V, not fluctuating, and I tested it with multiple power supplies.

There’s no short circuit in C14 or SW8. C12, C13, C15, and C16 are fine. The 7805 outputs the correct voltage (5V). I measured the voltages on the PCB according to the manual, and all are correct except for three, but I don’t know why these three are off. The attached image shows which values are incorrect:

Instead of -8.11V, it’s about -12V,
Instead of -8.08V, it’s also about -12V,
And instead of 2.16V, it’s 1.06V.

Does anyone have any ideas about what could be wrong?

 

I can have a look but cannot do so until after July 1st.

 

Does anyone have any ideas about what could be wrong?

Have you followed all of the instructions in the troubleshooting section of the manual?

 

Your voltage readings appear to be normal.
If the screen is white then it appears that the MCU is not booting properly.

With the screen not installed, the green TRIGGED LED should come on after about 2.5 seconds after releasing RESET.
Then it flashes on and off with a period of about 3 seconds.

With the screen installed, the screen is initially white for 1 second, then the LED is turned on and the screen displays the startup screen and Booting... on the bottom line. The LED will flash twice, about 1 second each time, and the booting is completed.

I think that you will need to get a working oscilloscope to get anywhere with this. If you cannot get your hands on an oscilloscope then a possible solution would be to purchase an already assembled and working DSO138. Then if you succeed in getting the kit version to work, you will have two DSO138.

Look over your board and look for shorting or bad solder joints.
Post well focused high resolution photos of both sides of your board and let's have a look.

 

I bought a DSO 138 kit and soldered it together, but when it gets power, unfortunately, I only see a white screen. The green LED blinks with about a 1-second period, and nothing else happens; pressing the reset button only restarts the LED blinking. I'm thinking it might be constantly restarting the entire circuit for some reason.

The power supply is a stable 9V, not fluctuating, and I tested it with multiple power supplies.

There’s no short circuit in C14 or SW8. C12, C13, C15, and C16 are fine. The 7805 outputs the correct voltage (5V). I measured the voltages on the PCB according to the manual, and all are correct except for three, but I don’t know why these three are off. The attached image shows which values are incorrect:

Instead of -8.11V, it’s about -12V,
Instead of -8.08V, it’s also about -12V,
And instead of 2.16V, it’s 1.06V.

Does anyone have any ideas about what could be wrong?

Hi Bob 007. Here.
I put one of these together a couple of months ago, with the same problem I discovered I had a bad U5 regulator. I replaced it and unit now works.