Zw horn help...

Don't know if this will help you, but I have found some helpful information at this website. http://www.tranz4mr.com/ZW_Page.html

Hopefully, someone else will answer your question more directly.

It does not sound like the rectifier disc. Since it happens on both throttles,  I would look at the interior of the ZW closely to see if it has been modified. If not, the problem could be with the tender.  Have you tried the tender on the B or C throttles?  There is no whistle circuit on them.  

Yes it does do it on the B and C also. So it couldn't be the rectifier discs. The tender works fine with a cw80.  Transformer doesn't appear to have been altered in any way.

Okay here's an update. I tried a diesel engine and it works fine. The whistling tender was an 8632 Starter Set tender. Maybe it's not compatible? I'm just curious what would cause the tender to receive DC power on the B and C throttles?  Seems strange.

Let's take this a little more logically:

You have a device (the tender) that you assume uses DC to make it whistle.  It whistles. You assume, therefore, that DC is being transmitted to it.  Other devices (Diesel) work fine with the same transformer.

Do you know for a fact that there is DC coming from the transformer? What did you use to detect and measure it? Meter, 'scope, etc?

I did not measure anything other than voltage output on the posts.  I'm assuming that it requires DC voltage to trigger the whistle and Horn functions.  Not sure if a air whistle is the same, but I'm almost positive all newer electronic Diesel's require DC input to activate the horn. The fact that the horn works on the diesel like it's supposed to, and the air whistle runs all the time led me to believe that DC voltage or some other phenomenon is happening to makes the tender constantly sound.

"The fact that the horn works on the diesel like it's supposed to, and the air whistle runs all the time led me to believe that DC voltage or some other phenomenon is happening to makes the tender constantly sound."

So, premise #1:

If the "...horn on the Diesel works [as] it's supposed to..." that would imply that DC is only generated and transmitted when it's supposed to be.

And, premise #2:

"...DC is happening...constantly..."

Do you see the inherent illogic of your observations?

Only when you figure out what, if any, DC is being transmitted, will you be able to solve the puzzle.

You need to meter all 4 of the ZW outputs, and the output of the CW80 and compare them.  Measure the DC component with the meter in the DC mode, both while the whistle control is activated and not activated.  Also, get a hold of the manual for the tender and see what in its design makes it whistle under normal circumstances.

Does the whistle blow as soon as you apply power?
Or is it only after you reach a certain voltage level (or throttle setting)?

If it is the second, it might be helpful if you could measure the voltage at which the whistle starts blowing.

The circuit board in the tender is bad.

C W Burfle posted:

Does the whistle blow as soon as you apply power?
Or is it only after you reach a certain voltage level (or throttle setting)?

If it is the second, it might be helpful if you could measure the voltage at which the whistle starts blowing.

The air whistle starts turning as soon as voltage is applied. As expected turns quicker and louder as the voltage is increased.

Chuck Sartor posted:

The circuit board in the tender is bad.

That crossed my mind. But it works fine with other Transformers. Cw80.    K line.

This is an electrical problem. It can be solved by starting at the beginning and determining all the electrical factors in the situation. 

"The circuit board is bad" is a good clue.  Use a variable AC supply, (the ZW will work for this) and then a variable DC supply, (create a simple one using a full-wave bridge, connected to some other transformer's output) and do a bench test of the circuit board. See what makes it go, by measuring the voltage thresholds.  But you still need to know what its requirements are, from the manufacturer's data.