Had a dead Soundcraft Ui12 needing repair. Was browning out any PSU connected.
Ruled out the CPU board and DSP board, meaning it was the analogue board.
Sheesh, three factory bodges! Early unit I guess?
Running it current-limited, the inductor for the 48V phantom power boost converter was getting warm.
desoldered the caps, and despite being bodgy, they weren’t dodgy.
Desoldered (and broke, whoops) the inductor just to confirm it was this section. Yep, board works fine without it! Next I need to find a replacement for this boost driver chip. And the jellybean inductor.
Super closeup of the boost driver chip, marked U51, 741F / L5002 / MA
Photo showing the board section before inductor was removed, with an electrolytic cap bodged on top of a large ceramic cap.
Closeup of a PCB showing a switch mode circuit layout, with the inductor missing. Below is an Atmel Atmega 48P microcontroller.