I appologize for the brevity of this section. The Mac II is covered in several areas in great detail. This area needs to be updated with general information I will get to it soon D.G.

 AC IIsi

The IIsi was a machine that was a downplayed IIci to lower the price. Sorry, but you did pay less. The machine is very durable but there is one small weak area that is so insignificant but not if you are experiencing it.

Sound
The speaker connections tend to corrode over time making the  connection intermittent or non existent.  It can drive you nuts.  Remove the cover and clean the connections with something that can scrape them if you're careful or go to Radio Shack and ask for an anticorrosive cleaner.