Challenge #9 · safety-circuits
The Whole Panel's Dead
You walk up and the machine is completely dead. No HMI, no pilot lights, nothing. Control power is gone.
① Run your checks
② Make the call
③ Explain your reasoning optional
A strong answer covers:
- What you did: confirmed control power is made (120V at the transformer secondary) and passing the control fuse, then checked the series e-stop string to the MCR.
- The reason: power is present and getting through, but the series safety string is open, so the master control relay can't pick up.
- Determined outcome: one open contact anywhere in the series string (a latched e-stop, tripped overload aux, open guard) drops the whole panel; walk the string contact by contact, don't replace the transformer or fuse.