I built one of those dso 138 oscilloscope kits and had issues getting it to boot when finished. Why did this repair/modification work? : r/AskElectronics
DSO 138 Osc DIY Kit Probe Calibration - YouTube
Adding Digital Channels to the DSO-150 Oscilloscope And Flashing New Firmware - Pagefault Blog
DSO138 oscilloscope
DSO 138 DIY Oscilloscope Kit Opening Source 2.4" TFT 1MSPS Digital Oscilloscope Kit with DIY Parts & Probe, Handheld Pocket Sized 13803K, SMD Electronic Learning Set: Amazon.com: Industrial & Scientific