My Post War 275 watt ZW Transformer outputs 17 volts for each of the four controllers at full power.
What is the "normal" voltage output for a ZW and how can I improve it?
Thanks
Original Post
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Early ZW transformers from 1948-49 had a 250-watt rating, the same as a Z. They also output slightly higher voltage than later ZWs, with a range of about 7-21 volts.
In 1950, Lionel released a revised version with a 275-watt rating. Its voltage output is about 6.5-20 volts.
Read more: https://dfarq.homeip.net/all-a...el-zw/#ixzz7OYDHtJ5P"
There is a fixed voltage 8V winding on the core that is common to all 4 channels. When people overload these transformers for long periods of time or other damage, the 8V winding begins to short and thus no longer produces the 8V. Put another way, raise the handle from 0V to the very first point power comes on. That should be 8V, If it's not and something lesser, then check for a poor connection point that may be high resistance where the 8V winding and 4 variable channels meet. If that is a solid connection, then measure the 8V winding output directly. Also, another symptom of a shorted or failed 8V winding is the transformer gets hot even with no load. In other words, just sitting there plugged in, the transformer would noticeably get very hot basically doing nothing.
Again, if you have the 2 worrying symptoms- this transformer runs hot even when just ON and not powering anything, and your base (first step) starting voltage on channels is less than 8V, that points to a failed and thus possibly shorted main core 8V winding.
Also, just a note about high resistance connection problems. I do not think this is your problem when measuring the voltage with a meter and no load on the transformer. The reason is- resistors or resistance resists current not voltage. Your meter is very high impedance and does not load the transformer with any appreciable current. Thus, just like I cringe when people complain they have a voltage drop on their track, but check with a meter and the voltage is fine - well yeah, the voltage doesn't sag from a high resistance connection until a lot draws current. So if under load (lights, a trains, a test load) you see a major drop- then that's a high resistance problem but you typically will not catch that fault with a meter alone.
Also, the list of common known faults I am aware of (obviously, there are many is this is not all inclusive):
#1 The U common terminal bus is just a crimped bus strip and the studs are crimped or riveted. With time and with usage, these can come loose either causing high resistance or just open circuit between U terminals. The fix is new threaded studs with nuts to capture and connect to the U terminal strip.
#2 This 8V winding being shorted and low voltage causing the transformer to also run hot. I had one customer who burned up more ZWs this way than anyone could imagine. They were just hard on transformers (frequent shorts and miswiring problems). Again, the big tell on these is they run hot even with zero load, and have a low starting first step voltage.
#3 High resistance connections but again these affect loaded output voltage, unloaded, the voltage doesn't sag when only tested with a meter.
#4 There also can be circuit breaker problems, but just like the high resistance junction, with only a meter as a load, this is not typically the root cause of low voltage. It's either open circuit and you get no output, or high resistance and you get sag under load, or the breaker itself trips or doesn't trip within specs.
Diagram
