Didn't hack it?
I used to wire up RCA jacks to the clockwise pin of the volume control pots of my equipment so I'd have line-out jacks. The best spot for line-in was usually trial and error by touching another device's line-out to anything that looked like a DC blocking capacitor near the microphone amp. The same soldering iron used for that wiring would be used to burn RCA jack mounting holes in the device too. I didn't have a lot of tools.