# ZW Transformer Whistle switch



## Fighterpilot (Mar 16, 2011)

Guys, just bought a used ZW transformer from my local hobby shop and Lionel Train service center. My pocket book is still hurtinghwell:hwell:The owner said he went through the entire Transformer and replaced everything that showed any wear with new stuff. I will admit, it runs my trains around my layout with much less variation in the trains speeds on grades. 
The one problem I'm having is it will not blow the whistle on either my Polar Express tender or my Williams Dash 9 Diesel. I believe it has something to do with the newer whistle in modern engines and tenders, but I'd like to hear from one of the resident experts that is aware of this problem.
I'm going to call, Mike, at Mike's Train Shop, as soon as he opens this morning to ask him about it, but I'd like to hear from someone here that has had a similar problem and can shed some light on the subject.
Thanks,
Bill


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## gunrunnerjohn (Nov 10, 2010)

Well, you have correctly identified the issue. It seems that when they shunt the rectifier to accommodate the additional current draw of a conventional whistle, it drops the DC to a low value that won't trigger electronic whistles.

I see the same thing with all the conventional transformers, some modern whistles work, some don't.

You can do a couple of things.

#1: I can usually get the whistle to go by turning the whistle control slightly for the first contact before the shunt kicks in. If that doesn't work, try plan-B

#2: Roll your own whistle/bell controller that will work 100% of the time. This is accomplished by using a handful of 3A diodes and a couple of pushbuttons.

Here's the whistle controller option.


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## Fighterpilot (Mar 16, 2011)

*Bells and whiltles*

Now Gunrunner, I'm a retired attorney, do you really think I know what all that means?:laugh: I guess if it were spelled out to me symbol by symbol, I could put it together. Does this go inside the ZW transformer or is it a separate unit that you build and just hook up betwee the transformer and the tracks? 
I really appreciate your attempt to help me, but I think this is a little far over my head in the electronices field. I'm happy to know there is nothing wrong with my transformer and that is just the way it was built, that is doesn't function with the newer electronic horns and bells.
Thanks,
Bill

PS: After looking at your diagrahm again, it really is simple and I think I could put it together; but, could you identify each of the symbols for me with a description of what I need to buy and what is the multidirectional diode connected between the Neutral and Positive lines just before it connects to the tracks. I also need to know what size fuse you are fusing the Positive lead with coming off the transformer?


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## gunrunnerjohn (Nov 10, 2010)

The TVS for spike suppression isn't really necessary. 

Here's some 3A Silicon Diodes for .27 each, and Digikey charges very reasonable and actual shipping charges, probably a couple of bucks for a bunch of these.

This is a separate box with the diodes and the two push buttons. You can experiment with the number of diodes, I have done this with three diodes on each let and it worked great. The key is where there are multiple diodes, you can vary that number, but you have to have a single diode as represented on the other side of the switch.


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## Fighterpilot (Mar 16, 2011)

What size and type fuse do you have as you come off the transformer? Is this the set up for the ZW transformer and is the only connection to the track or is it a parallel connection to the track along with the wires running directly from the transformer to the track?

As I understand what you have done is 3 diodes on each side ( bell side and whistle side) inside the switch circuit, with one diode on the load side of the switch on both the whistle and bell circuits. I do not need the TVS, correct?

Pardon me if I keep asking questions; but, I've never done this before and I want to make sure I've gotten everything exactly correct.

Regards,
Bill


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## gunrunnerjohn (Nov 10, 2010)

This example has five diodes in the switched string, you can reduce that to three or even two and still have the horn function. The reason you might want to reduce it is they drop voltage, so you'll have to crank the transformer up higher for the same power, less diodes drop less. You don't need the TVS, though it's not a bad idea. I have no fuse off my transformer, though I'm considering adding one. For my real layout, I'll be adding the TVS diodes as well, since I'm going to have a bunch of expensive electronics running around the tracks.


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## Fighterpilot (Mar 16, 2011)

Mind you, I don't know what any of this stuff is and I'm planning trip to Radio Shack tomorrow. What is a TVS diode. I know what the other small diodes are, in that they reduce voltage and only allow current to travel in one direction. Again, what size fuse are you going to put in front of this device and I take it this is the only connection between the transformer and the track, so any splitter carrying current to various parts of the track to reduce voltage drop should be connected on the load side of this device.
I'm beginning to feel like a dog chasing his tail here, so please bare with me and try to answer my questions, if I'm making any sense at all, so I won't keep posting here and sounding like Ned and the first reader..(which I am when it comes to this train stuff)


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## gunrunnerjohn (Nov 10, 2010)

Well, I'd probably exercise a little patience and order from Digikey at the link I posted, Radio Shack gets a lot more money for their diodes.

This is the TVS Diode that is suitable, you can get it from the same place, Digikey.

You can put whatever size fuse you like there, depending on your maximum load. If you want to full capacity of the ZW transformer, you'd probably have at least a 15A fuse, though you could use a smaller one for lighter loads and better protection. Remember, you're only running a single train through this device, so the fuse should probably be sized to reflect that. I'd start with a 10A and see how it goes.


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## Fighterpilot (Mar 16, 2011)

Gunner, thanks a lot for the information. I'm going to try it and I'll let you know how it works. Patience...huh, you nailed it my friend, I've never been one for patience. When it needs to get done, I dive in with both feet. Shouldn't cost me more than an extra $5.00 at Radio Shack and I won't have shipping to pay. 
Next question.....I know, I know, .....not another one.. in what did you build this device? Is there some sort of box that it can be neatly assembled? I'm going to try it with the two diodes in the string and one on the load side of each of the buttons
I'll let you know how it works when I get it built.
Right now I'm starting to roll newspaper and plaster the sides of my grades. My test area is drying tonight so I can see how it looks in the AM.
Later,
Bill


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## tjcruiser (Jan 10, 2010)

Fighterpilot said:


> Is there some sort of box that it can be neatly assembled?


Bill,

I have an EMPTY old Lionel whistle controller box (with back plate) ... looks like the link below ... no red buttons, no guts. I have no idea if it would be suitable to what you and John are discussing, but if you want to give it a shot, it's yours for just the price of postage.

http://www.postwarlionel.com/cgi-bin/postwar?ITEM=167

TJ


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## gunrunnerjohn (Nov 10, 2010)

You can find small "project boxes" either on-line or at Radio Shack, I used one that was 3 x 4 x 1 when I did this. I used a total of 8 diodes, three in the strings shunted by the switches, and one in the circuit all the time. It worked great.

I would post pictures, but that was given to a friend when I started going all TMCC.


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