When nothing happens
Almost nothing goes wrong on this board, which is exactly what makes it frustrating: the symptom is always the wrong voltage and the cause is always somewhere else. Three measurements find it.
Three measurements, in this order
The order matters. The first is safe with nothing connected and tells you whether the board did its job. The second needs the load and tells you whether the supply can hold up. The third is done with the charger out, and is about your wiring rather than the board.
What each answer means
The terminal reads what you asked for, unloaded. The board has done everything it does. Anything wrong from here is downstream — your wiring, your load, or a connection at the terminal.
The terminal reads 5 V. The request did not happen, or was refused. In order of likelihood:
- the levers are not what you think they are — check them against the table;
- the charger does not have that rail — check the printing on its case;
- the cable is charge-only and has no CC conductor — swap it.
The terminal reads 0 V with the LED lit. VBUS is reaching the chip but not reaching your probes. The usual cause is a screw clamped onto insulation rather than copper.
The LED is dark. No VBUS at all. Try another cable, then another charger, then another board, in that order, because that is the order of likelihood.
What is not worth checking
The chip has no firmware, no configuration to be lost and nothing that can be programmed wrongly. There is no reset, no enable pin and no state to clear by power cycling — everything it does is decided by three levers and redone from scratch every time the cable goes in.
So there is never a reason to suspect a board of having "got into a bad state". If two boards set the same way on the same charger behave differently, one of them has a physical fault, and with twelve in the bag the right response is to put it aside and carry on.
When it does not work
The request was refused or never made. Check the levers against the table on the back of the board, check that the charger's case lists 12 V, and swap the cable for one you know carries data. Those three cover almost every case.
Look at the LED. Dark means no VBUS: a charge-only cable, a dead charger or a bad socket joint. Lit with 0 V at the terminal means the output pair is not connected to what you are measuring — check that the screw actually clamped the wire and not its insulation.
Measure at your circuit rather than at the board. A terminal screw tightened onto insulation, a wire that broke inside at a bend, and reversed polarity all give you a correct reading at the board and nothing at the other end.
Set two boards to the same voltage and swap them on the same charger and cable. If the difference follows the board, that board has a fault and you have eleven more; if it stays put, the fault is in the charger, the cable or your wiring.
The other end of the same question: what a bare USB-C socket gives you, and the two resistors that make a charger hand over 5 V at all.
The USB-C breakout handbook →Edit this page — content/books/pd-trigger/when-nothing-happens.mdx
Questions about this product
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USB-C PD Trigger, 100 W Decoy 5–20 V, 12-Pack
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