Reply To: v.1.7 not working even after JTAG flashing; how to debug?
NewHome › Forums › OSSC, OSSC Pro and DExx-vd isl › OSSC – DIY & Repair Support › v.1.7 not working even after JTAG flashing; how to debug? › Reply To: v.1.7 not working even after JTAG flashing; how to debug?
This guy also had a broken U6 regulator. https://videogameperfection.com/forums/topic/trying-to-repair-a-dead-ossc-u6-and-u1-were-replaced-boots-but-no-test-pattern/
Aha, I know 1 thing that’s broken for sure: the PCM1862 ADC (U8). I injected 3.3V externally through the U6 regulator output pin and it draws ~10A ! I touched all the chips that it powers and only U8 got hot. U1 is hard to tell because it’s so big and will take a long time to heat. That makes sense U8 got damaged, assuming that’s what the analog audio input connects to – I see pins named I2S in ossc_board.pdf, so that means audio.
This seems to be a case of permanent latchup. I’ve seen many microcontrollers ruined by latchup, presumably from applying signals before power, causing the gate voltage to exceed VDD.
Before I replace components, is it expected for the firmware to not print anything on the LCD? Does it mean it’s stuck forever reading/writing I2C and not getting a response?
