This unit was given to me many years ago but the battery was dead and I left it untouched a long time. I then needed to charge a car battery but it's not performing the job. I would like to diagnose the unit and repair it if not too costly. The power cable is missing but I connected it to the AC line by means of a broken extention. The cables to the battery can't get to the poles of the battery and I used "probably" a too thin couple of cables. I know this has an effect on the power getting to the battery but... Need ideas as to how to proceed! Thanks in advanced for any help on this issue!