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Zw whistle problem.

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Zw whistle problem.
Posted by Michael6268 on Friday, July 21, 2017 9:33 PM

I picked up a clean ZW Transformer. I put an air whistle tender on the track and it runs constantly with increased voltage from any of the throttles. Using the whistle lever increases the whistle slightly. But the whistle is always going. I tried a conventional diesel horn with the ZW and it works fine.  The tender is a basic Starter Set tender that came with an 8632 steamer. Any idea what could be setting off the air whistle all the time? It runs constantly.  It would seem to me that DC current is being introduced to the track. But if that were the case the diesel horn would go off all the time also.  The tender works fine with a cw-80 Transformer.

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Posted by Firelock76 on Saturday, July 22, 2017 8:50 AM

The problem's with the whistle tender, there's something about the juice coming from your ZW it just doesn't like, especially if it works fine with a CW-80.  Now, I'm not familiar with the 8632 steamer, but I've had some current (recent) production Lionel whistle tenders do exactly the same thing with my MTH trasnformers.  In my case circuit boards in the things went bad so as soon as the track was powered the whistles ran constantly.  Why? Who knows why?  They're circuit boards, they could last 20 years or blow tomorrow, you just don't know.

My solution was to replace the whistle units with some Williams steam whistle kits, which have worked perfectly, plus I get bell sounds too.

You could always shop around for a vintage Lionel whistle tender that's "orphaned" and needs a home.  I've done that too.

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Posted by lionelsoni on Saturday, July 22, 2017 12:31 PM

Is this ZW a real transformer, or the modern power supply of the same name?

Bob Nelson

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Posted by Michael6268 on Saturday, July 22, 2017 1:09 PM

Its a postwar ZW R.

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Posted by TrainLarry on Saturday, July 22, 2017 4:33 PM

Sounds like the circuit board is bad.

Part #610-8633-010

The Train Tender stocks it.

 

Larry

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Posted by lionelsoni on Saturday, July 22, 2017 7:56 PM

Does it misbehave in the same way whether using output A or output D?

Bob Nelson

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Posted by Michael6268 on Saturday, July 22, 2017 8:38 PM

lionelsoni

Does it misbehave in the same way whether using output A or output D?

 

 

Actually it does it on all the posts.  A-B-C-D....

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Posted by lionelsoni on Sunday, July 23, 2017 12:19 PM

It seems very unlikely that the transformer is the problem.

Bob Nelson

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Posted by BigAl 956 on Tuesday, July 25, 2017 1:37 PM

Michael6268
Actually it does it on all the posts.  A-B-C-D....

Most likely a problem with the tender.

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Posted by Michael6268 on Tuesday, July 25, 2017 4:24 PM

I misspoke in my first post. Turns out that the whistle on the whistle tender doesn't kick in until around 15 volts and up. Below 15 volts it's fine. Reacts to the whistle levers like it should. Albeit a little weak. I assume because of the original rectifier discs. I'm going to put diodes in at a later date. I never run a conventional engine at that high of a voltage anyways, so it shouldn't be a bother. I'm still just curious how ac voltage could trigger the whistle. I always was under the assumption it was DC voltage that triggered the whistle.

 

Also. Is it very difficult to get the housing off where the diodes go in?  Looks like a lot of wiring/ resistors that don't have much give are in the way.

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Posted by lionelsoni on Tuesday, July 25, 2017 8:28 PM

DC voltage is indeed what is intended to set off the whistle.  The design problem is how to know when that DC voltage component is present.  It doesn't work to assume that there is DC there if the instantaneous voltage is not zero, because the instantaneous voltage of an AC waveform is also not zero except for two instances every cycle.

The practical solution is to compute some sort of average of the voltage over a time long enough that the positive and negative parts of the AC waveform will cancel each other, but not so long that there will be an annoying delay in blowing the whistle.  The original whistle relay does this with a solid copper slug near the end of the relay's core nearest the armature.  In a modern tender, the averaging is probably done with a low-pass filter, probably a series resistor and a shunt capacitor.

But, even if the averaging circuit or relay may greatly reduce the amplitude of the AC voltage component, if you put enough AC voltage in, a little bit will get through and make the whistle blow.  Lionel specified that if this happens at an RMS AC voltage less than 28 volts, the relay is defective.  I would hold an electronic whistle to a similar standard--15 volts is too low.

Bob Nelson

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