After posting my message I checked the unit again and found on the bottom of the case a
note stating that the unit was custom wired and would exhibit the faults I mentioned.
I find it hard to believe that he actually left a note in there to tell you what he did, and what's wrong.
Most of the time when you purchase something used, on Ebay or Agon, you are taking a risk. When your purchase turns out to be imperfect, you can either eat it, or fix it yourself, because chances are the sellers would advertise "as is" "no return" "it worked before I packed it", "it worked last time I used it" " no guarantee" and so on.
I bought a lot of gear used, and sometimes you can tell how honest the seller is by how his ad's written, but sometimes not, and pictures don't tell the whole story. I had equipment that I bought off Ebay or Agon that I had to put in some labor to make them to work right. Of course, sometimes I got real lucky and bought something better than what I thought.