Reply To: No LEDs, Faint LCD Backlight, Suspicious U12/VCCINT, nSTATUS

NewHome Forums OSSC & OSSC Pro OSSC – DIY Support No LEDs, Faint LCD Backlight, Suspicious U12/VCCINT, nSTATUS Reply To: No LEDs, Faint LCD Backlight, Suspicious U12/VCCINT, nSTATUS

#10216
dfwarden
Participant

This story has gotten very strange. After cleaning the board with alcohol and testing various points for connectivity, the board suddenly started working long enough for me to flash 0.74 with a USB Blaster. I started to add the remaining connectors (re-testing after each one) and after adding the audio the board no longer booted.

I tried putting U14 from the old board on U12 of the new board and with the output legs raised I still read about 1.35v. I even tried putting U14 from the new board on U12 and got the same result, which surprised me because U14 on the new board works fine. The only explanation I can think of is that the FPGA is now so damaged that something about it caused the a working regulator to fail even with the output legs raised.

At this point I don’t have any other ideas but to accept your diagnosis of bad TLV70012s from Mouser US and probably busted FPGA. Is there a way to tell for sure if the FPGA is gone?

Do you have any advice on making sure the replacement U12 is working correctly? If I only connect the 3 input pins, should I read 1.2v? Should the presence of the FPGA, regardless of if the U12 output pins are connected, affect the output of U12?