I think cjaceks pictures tell the story quite nicely. (Good score)
I recently bought a 388, and then almost immedately had the chance to buy a 2nd one "sight unseen" for parts or repair, as the seller says it would not record.
Turns out the "parts" 388 works perfect (yay...clueless, but honest seller) and is actuallly nicer than the first one! I am pumped about the 388 !!
Probably the most important thing, other than pure cosmetics, is the tape transport and heads. Not much can go wrong or out of adjustment with the mixer section. If you have one of those little pocket tone generator (or a mic)you can plug into each mic input to confirm signal on all channels, that will probably tell you all you need to know about the mixer.
Head condition may be hard to discern, so look also at the tape lifter and guides to either side of the heads for wear or grooving....they would ideally looked like cjackeks pictures, i.e. no wear. Run a tape on the transport, look for good acelleration on the FF and RW functions, proper function of the counter tach, solid engagement of the pinch roller, good brakes, smooth operation and tape movement, etc..
Good luck, and make sure you get a manual one way or the other
