The transformer on my HO set shut down the other day as soon as I plugged it in (after not being used for months). I got my volt meter out and tried to find where the short was. I tested each building/street light individually. To my surprise, what I found was about half of all the lights made my volt meter beep (meaning the two leads from each light were crossed somewhere). Is this normal? Or does it mean the lights need to be replaced? Thanks in advance.