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ZW COIL PROBLEM

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ZW COIL PROBLEM
Posted by stuartmit on Monday, March 23, 2015 7:42 AM

MY zw is not shutting track voltage down to zero, at least on the two big outer throttles. I had this once before, and I wathched a guy repair it--It seem as if there are  retaining male  "stubs" which slip into to molded outcroppings which create a female in the body to receive these stubs.. When the coil in some way gets out of that retaining mechanism, the coil moves in such a way that the rollers never get down to the end of the coil where there is no voltage. I watched the repair  done, but when I opened the case (with the plug out of the socket!) I didn't see anything at all that seemed to be the Male/femle structures I thought would see.  Any expertise here? 

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Posted by stuartmit on Monday, March 23, 2015 8:05 AM

Just looked in Olsens Toy Trains Library and see the that the coils is supported by metal retaining plates that seem to support the coil in back of case, and in front. and it seems as if the coils drop downinto a recatangular cutout which receives the ends. if that is the nature of the mounting, then if these plates should spread apart slightly, then the coil could slip into misalignment relative to the roller arms and give rise to the condition. I am absolutely sure that when I had this problem it was easily repaired by correcting the relative postions of the two elements--the coil and the support. I have wired my own kitchen, with inspection so I feel competent to do this repair, but I am not sure at all about what I should be looking for, how it probbaly looks in current malfunction, and how it should look when returned to proper position.

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Posted by TrainLarry on Monday, March 23, 2015 11:45 AM

There is a picture of the ZW coil in it's bracket here.

It is doubtful that the coil could become misaligned, as the coil support straps would keep the support brackets in line.

Some transformers do not shut down all the way to zero volts, and may have a few volts on their output even with the control arm all the way off.

What voltage are you getting with the handles in the off position?

Larry

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Posted by servoguy on Monday, March 23, 2015 12:24 PM

The ZW should shut down to zero volts when the handles are in the off position.  There is an area that the rollers roll onto that is an insulator.  Look to see where the rollers are when the handles are in the off position.

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Posted by stuartmit on Monday, March 23, 2015 3:36 PM

other info: The eunit will cycle when the handles are on, and the reverse button is pulled to that interrupting position using to stop or start the train, but when the handles are in the off position, operating the revers control in that same way does not cause the  e unit to cycle; the loco's light stays dimly lit and the circuit stays alive, but not sure; not sure my multi meter will read 7-8 volts  but I will try. It does strike me that I have some accessoriey on the b and c rings; maybe there is a feedback loop of which I am unaware; I will check that this pm by disconnecting those feeds.

 

but thanks for your comments so far.

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Posted by TrainLarry on Monday, March 23, 2015 4:52 PM

Disconnect the wires at the transformer and check the voltages.

Larry

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Posted by lionelsoni on Monday, March 23, 2015 6:24 PM

If you are using a modern voltmeter, which may have a very high input impedance, shunt your meter with, for example, a lamp while making voltage measurements.  Otherwise, you may be reading voltage capacitively coupled to the wiper, even though the wiper to secondary winding connection is open.

Bob Nelson

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Posted by stuartmit on Monday, March 23, 2015 8:34 PM

Completely do not understand last post

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Posted by TrainLarry on Monday, March 23, 2015 9:07 PM

After disconnecting the wires to the transformer, and with the handles in the off position, connect a bulb across the A-U terminals before taking a voltage reading. Connect the bulb to the B-U terminals and do the same thing, then do C-U and D-U.

Larry

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Posted by stuartmit on Tuesday, March 24, 2015 5:17 AM

I notice in the pics of ZW parts posted by trainlarry that on the retainer brackets for the coils, there is a tongue of metal which is in the center of the cutout which accepts the core on each end. I have my ZW mounted on about a 30 degree angled top panel and the core under the action of random house vibrations and gravity wants to slide downward parrallel to the angled mounted base of the ZW. It seems to me that becasue this tongue is not bent at 90 degrees, but in two bends-may 60 and 30, there is room for the core/coil assembly to slide down because there is a greater distance between the coil retainer brackets than the length of the core. This    means the power arms which are fixed in place now do not go off the end of the winding to the insulating area referred to in a previous post which creates zero voltage in the off position. If the Z were mounted on a surface parrallel to the floor the core would be under no impetus to migrate in that way. But I believe I have seen photos of other similar mountings. What comes to mind is the 1949 showroom layout--am I making that up?  At any rate, I am not at 26th street in 1951 (damn Bobby Thompson) I am in New Jersey in 2015 and I can't get my Zw to go to zero volts!

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Posted by cwburfle on Tuesday, March 24, 2015 7:04 AM

The bends in those tabs in the middle of the "U" shaped opening should be pretty much at a 90 degree angle. The transformer core should not be able to shift in the bracket.
If the core can shift around in the bracket, and/or those bends are not at approximately 90 degrees, then I suggest you have someone who is familar with the insides of ZW transformers take a look at it.

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