ZW transformer diode installation
1- Start by removing the cover 4 screws and remove cover.
2- Locate the rectifier frame & lamp bracket assembly on each side.
(see chart below)
Most customers are able to install the diode without completely removing
the bracket from it’s mounting – the trick is to get the nut started behind
the bracket and to hold the nut as the diode itself is tightened.
The recommended tool for this task is a pair of 90 degree needle nose
pliers to hold the nut.
If you cannot install the diode in this way please continue.
3- Start with the left side - it is in front and therefore somewhat easer.
At this point I would recommend taking several pictures of the internal
wiring before starting and any time a wire or part is removed during each
stage of disassembly. Pictures don’t forget, as there are variations in ZW
wiring depending on the model.
4- Remove the two screws and lift off the rectifier and lamp bracket
assembly with wires attached if possible or remove wires and reposition as
required to gain access to the whistle parts mounted to the bracket.
Use caution not to damage the fiber contact spring insulation under this
bracket, take note of the position of all parts during disassembly.
5- Remove the old whistle parts (see chart below) – pin, fiber washer, fiber
spacer, rectifier disc, and speed nut with wire attached. Install the
replacement diode threaded shaft into the large hole on the bracket and
secure with the nut on the rear of the bracket (the bracket hole is larger
then the diode shaft this is not a problem)
7- Attach the wire from the speed nut to the solder lug of the diode.
8- Make sure the contact spring; contact spring insulation and tube
insulation are correctly in place over the throttle shaft.
9- With a flat thin tool hold down the contact spring and insulation in place
as you install the bracket on top of them. Align the bracket with the pins
and start a screw. The tool will be between the insulation and the bracket
during initial alignment.
10- Please make sure the contact spring and contact spring insulation has
not shifted. Don’t force anything it will fall into place when correctly
When sure everything is aligned hold the bracket in place with your finger
and slide the thin flat tool from under the bracket and start the other
bracket screw, recheck alignment and secure both the screws.
11- Repeat the process for the other side.
If the insulation becomes damaged they are available from replacement parts
suppliers on line.
Lionel part numbers are tube insulation (rectangle with 4 holes) ZW-81
contact spring insulation ZW-163
It is also very important to check for condition and repair all the
transformer wiring as needed .
After 50 or so years the original wire insulation may have failed and
could cause a dangerous condition.
By installing the diode YOU take the responsibility for the
operation and repair of your antique transformer.
These instructions are for information only.