I'm trying to troubleshoot a serial Optipac and Happ trackball.  This setup was working at one time, now it is not being detected in Windows as a mouse.
Using my multimeter, I am getting the 5v from the PC to the +5v on the Optipac power input terminals.  What should my reading be on the Player 1 +5v terminal?  I'm assuming 5v, but I am only reading .16 on the multimeter.  
Could there be a problem with the trackball or Optipac?  What would be the next step for troubleshooting?
Thanks.