I have a Lionel KW transformer with a nonfunctioning whistle/horn switch. This switch is operated by giving about a 1/4 turn to the left or to the right, depending on which side of the transformer is connected to the track, on an orange lever on the top of the transformer, located between the direction buttons. The transformer power cord has been replaced and it operates my antique toy train satisfactorily with both operating levers. My goal is to restore this transformer to it's original operating capablilties. I have no interest in using this transformer for newer model trains with yard and train sounds. I simply want to repair or replace this switch, if possible, so it will operate the horn on my GM D3 Santa Fe Locomotive set. Are there any instructions available to get me started on this repair? I do know how to remove the cover of this unit. Thank you for any help.
I assume the whistle control doesn't work on the A or B side of the transformer. The most likely problem is a bad copper oxide rectifier. You can replace the copper oxide rectifier with an ordinary silicon diode. You can buy a diode at Radio Shack for a few dollars. You need a diode that can handle at least 5 amps and 50 volts. You will have to remove the copper oxide rectifier and replace it with the diode. I have 4 KWs and 2 ZWs and have replaced most of the copper oxide rectifiers. Some guys on the forums recommend using a stud mounted diode as it is easier to install than a smaller diode. You might check eBay for diodes and instructions. It doesn't matter about the polarity of the diode. The whistles don't care.
While you have the transformer apart, lube the whistle control with motor oil, 5W-20. The KW whistle controllers have a lot of friction, and lubing them makes them work much easier. One of my KWs has a broken part in the whistle control which I managed to repair. Lube will prevent breakage of the whistle controller.
Be aware that the Lionel service manual makes no mention of lubricating the whistle switch. Wet lubricants attract dirt/grit.
You can find the KW transformer service manual pages at Olsens:
http://pictures.olsenstoy.com/searchcd31.htm?itm=657
Is the horn on your locomotive known to be functioning? There could be a problem with the horn circuit in the locomotive that is causing your issue, or you may have both a locomotive and a transformer problem. You need to test the horn circuit manually to see if it works.
Larry
One more thought: the whistle control switch casting is subject to Zinc Rot and a lot of stress. The last time I needed one, they were not readily available. The only replacements I could find were at Brasseur trains, part number 20-70A. If you need one, I suggest getting a new retaining clip too.
http://www.traindoctor.com/service/lionel/0to120.php
It is true that the polarity doesn't matter--for older locomotives with relay-operated whistles or horns. But, if you think that you or anyone else will ever want to run modern locomotives with electronic whistles using that transformer, you might as well put the diode in so as to make the center rail more positive than the outside rails. Note that Lionel's schematic diagrams always showed the diode incorrectly, that is, with the cathode toward the center-rail terminal, even though the actual transformers were built the other way around.
Bob Nelson
You guys are the best. Larry, I fixed the horn myself. It's not "like new" perfect, but it works. I've got a spare "K" Line Transformer, and that operates the horn fine. It looks like I'll be replacing a copper oxide rectifier with a silocone diode. And I'll have a look at the whistle control switch casting. This is my first venture into repairing toy trains. This is our (I have 3 siblings) childhood Lionel Train set. My sister had it, let it become junk, and turned it over to me. I couldn't stand to see my old friend in that condition, so I decided to see what I could do with it. You all have helped me get the #50 Section Gang Car running, I repaired the 6019 uncoupler track switch, and I got the Stockyard working again with some new vibration washers. I learned how to repair the horn from an internet video. This experience has been fun. Thank you all.
See my 2015 post above. If the troublesome transformers have been repaired without concern for the diode polarity, that could explain what you're seeing.
Postwar whistles were activated by the mere presence of a DC component in the track voltage, without regard for the DC voltage's polarity. So the whistle would work no matter which way the transformer was connected to the track. Nevertheless, Lionel consistently oriented the diodes so that the center rail was more positive than the outside rails when the whistle control was operated with the transformer's common connected to the outside rails.
Modern locomotives generally require that the center rail be positive to blow the whistle. So an old transformer repaired without concern for the diode polarity may fail to blow a modern whistle. And an old transformer conscientiously repaired by someone who doesn't know that the Lionel schematics are consistently incorrect with respect to diode orientation will certainly not blow the whistle.
Thanks Bob for your reply. I'm not an electronics guy but I did open up my offending ZW and did not find anything that looked like a diode but my "A" roller is just about used up. The transformer doesn't look like it was serviced before but I'm not the original owner. I also looked at the wiring diagrams in the Service Manual and found no mention of diodes in either the KW or ZW transformers. The wire colors seem to indicate I have a Type R ZW.
I'm afraid we have been blindsided by the evolution of technical terms. The term that Lionel used for what I called a "diode" was "rectifier".
A "diode" was originally a vacuum tube with two elements, used as a rectifier. (A "triode" had 3 elements, a "tetrode" 4, a "pentode" 5.) There were also solid-state rectifiers, like selenium and copper-oxide, the kind that Lionel used. With time, germanium and silicon rectifiers replaced vacuum tubes and came to be called "diodes". (The "reference designation" for them on schematics changed from "CR", meaning "crystal rectifier, to "D".) The term "rectifier" is now used in a more general sense, as a circuit that rectifies, and may include multiple diodes and other components to accomplish that task.
The symbol for a diode (in the modern sense) is
Current flows in the direction of the arrowhead. The left terminal is the "anode", the right terminal is the "cathode". The cathode is often marked by a ring around the diode's body. (Diode symbols are reversed on Lionel schematics.)
Thanks again. I now understand what is happening. I need to replace the copper disk with a 16 AMP stud diode. In the interim I hooked up a 167C whistle controller and the horn works. I saw a YouTube video showing an already installed stud diode on a KW. It appears that all that was done was the disk was removed and a diode was inserted in the hole and held in place by a regular washer and a nut. I see that the diode looks like it was soldered from inside the rectifier box I don't know what had to be done from behind to remove the copper disk. Another video of diode replacement on a ZW indicated that the box had to be removed but again never showed what was done.
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