Reibun
、。

While repairing a broken radio, I realize all over again that I don't understand how circuits work.

Literal

Broken radio [object-を] repairing-[while-ていて], circuit [possessive-の] operating-principle [object-を] understand-not-able-[state-ていない] thing [to-に] anew notice.

An honest moment of humility. 動作原理 ('operating principle') is a technical compound. The chain 理解できていない uses potential ~できる + ongoing state ~ている + negative — 'am in a state of not being able to understand.' 改めて気がつく ('notice anew') captures a fresh realization about a persistent gap.