I was recently given a type “Z” transformer. When I get a new transformer I usually look it over and test it on my 5D tester to see what condition it is in. I also like to open up transformers with carbon rollers to check the condition of the rollers. On type “V” and “Z” transformers this is difficult as the case screws are under the name plate, which is held on with drive pins. The first thing I noticed on this transformer was the name plate was held on with binding head self tapping screws, so the cover was easy to remove.
As soon as I removed the cover I could tell this was different than other type “Z” transformers I have worked on. The first surprise was that in testing with a meter I discovered that the voltage range was 0 to 24, rather than 6 to 24, which is more typical in post war transformers. The 6 volt at start up is to get the e-unit to operate before the loco starts to move. This 6 volts on start is achieved with an additional 0 to 6 volt secondary winding in the transformer. The other secondary winding is the one wound with square wire that the rollers run on. It provides 6 to 24 volts and is in series with the 0 to 6 volt winding. On transformers with whistle controllers there is a third secondary winding to give the 5 volt boost, but “V” and “Z” transformers do not have whistle controllers. In this transformer there is an additional secondary winding, wrapped with very small wire, which only powers the green pilot light at 6 volts.
The “Z” transformer was made prewar from 1938 to 1941 and I am assuming that this transformer is from that era. The 0 to 24 volts is still a surprise for me as the postwar style e-unit was well established by 1938. If anyone has more information on this transformer I would appreciate hearing it. Also if anyone has a wiring diagram I would like to get a copy. Thanks, David Johnston
