。
I'll have this radio fixed tomorrow.
Literal
Tomorrow this radio [object-を] repair [favor-receive-て] receive-let's-もらおう.
修繕してもらおう combines the verb 修繕する ('repair/mend') with the benefactive ~てもらう ('have someone do for me'), and the volitional ~おう ('I'll X'). The whole thing means 'I'll get it fixed for me / have them fix it.' Japanese handles 'have X done' through the benefactive system rather than a causative — no 'let' or 'make' verb needed.