American Flyer 12B transformer

[Chester]

I have just purchased a12B transformer.  The constant voltage works fine registering16.86 volts on the voltmeter; however, the variable voltage registers at ~ 7.5 volts when the speed control switch is at 0 mph.  As the control switch is moved to a higher speed, the voltage drops.  This happens with both speed control switches.  The rheostat appears clean and the switch contacts are clean and swing across the rheostat fine.  What could be causing the voltage drops?  I would expect the resistance across the rheostat to decrease as the control switch is moved to a higher speed.  This is not the case with this transformer.  Any constructive suggestions to remedy are welcomed.

Thanks,

Chester

[cwburfle]

Lionel (other than HO) and American Flyer transformers do not use rheostats. The voltage is controlled by a wiper brushing across the transformer's secondary winding, which effectively changed the number of turns in the secondary, hence the voltage.
If the voltage is dropping, it is likely because you are using the incorrect terminals.

I don't have a diagram or manual for a 12B, but I found a good picture on Ebay.
You should be using terminals on the same row.
Looking at the terminal plate, the posts  to your left should be labeled "Base Post".
The posts to use for variable voltage (7-15 volts) are the base post, and the center post.
Connecting wires to the center post and the right hand post would likely give you 7or 8 volts with the handle in the "off' position, with the voltage dropping as you moved the handle to increase the speed.

Maybe the lettering is worn off your terminal plate.
Here is the Ebay lot with the good picture of the terminal plate:

http://www.ebay.com/itm/American-Flyer-Transformer-Model-12B-used-on-my-Fleischman-O-Marx-0-layout-/381046100466?pt=Model_RR_Trains&hash=item58b81e11f2

[Chester]

Ahhhh, yes!!!  You are correct... I changed my base post to the opposite side and it worked!  The funny thing is that the connection panel on my transformer is upside down.  It appears that it was manufactured this way because the panel is riveted (see attached pic in tinypic link below).  Your reference to the ebay pic was very helpful.  Thank you for responding so quickly and the explanation and tips!  I can live with the flipped panel - so glad it works!

http://tinypic.com/r/10qla9u/8

Thanks,

Chester

Sent from my iPad

On Nov 16, 2014, at 11:00 AM, Toy train operating and collecting - Automated Email <[e-mail]> wrote:

RE: American Flyer 12B transformer

Reply by cwburfle

Lionel (other than HO) and American Flyer transformers do not use rheostats. The voltage is controlled by a wiper brushing across the transformer's secondary winding, which effectively changed the number of turns in the secondary, hence the voltage. 
If the voltage is dropping, it is likely because you are using the incorrect terminals.

I don't have a diagram or manual for a 12B, but I found a good picture on Ebay. 
You should be using terminals on the same row. 
Looking at the terminal plate, the posts  to your left should be labeled "Base Post".
The posts to use for variable voltage (7-15 volts) are the base post, and the center post. 
Connecting wires to the center post and the right hand post would likely give you 7or 8 volts with the handle in the "off' position, with the voltage dropping as you moved the handle to increase the speed.

Maybe the lettering is worn off your terminal plate. 
Here is the Ebay lot with the good picture of the terminal plate:

http://www.ebay.com/itm/American-Flyer-Transformer-Model-12B-used-on-my-Fleischman-O-Marx-0-layout-/381046100466?pt=Model_RR_Trains&hash=item58b81e11f2

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