RW Transformers in the accessory power box

["Ira Schneider" <ira_schneider@iname.com>]

Scott,

I have investigated the internals of the RW transformers we are using for accessory power.
The source of my information is the Lionel Service Manual that Jim Smiley showed me at our
Fun Run today.

The transformer actually contains four (4) secondary windings.  The first winding is a 9.9 volt
winding with a slider running from top to bottom.  The top of this winding is connected to terminal D.
The bottom of this winding is connected to the input of the circuit breaker.  The output of the
circuit breaker is connected to the top of the 6.1 volt winding (see next paragraph) and to terminal C.
The slider is used to select a voltage between 0 and 9.9 volts, depending on the position of the control knob.
This variable voltage is connected through the Direction button to the Whistle button.
When the Whistle button is not pressed, the slider is connected directly to terminal U.  (I won't
describe what happens when the Whistle button is pressed - it is too complicated and it has
no relevance to our use of these transformers.)

The second winding is a 6.1 volt winding. The top of this winding is connected to the output of the
circuit breaker.  The bottom of this winding is connected to the top of the 2.8 volt winding (see
next paragraph) and to terminal B.

The third winding is a 2.8 volt winding.  The top of this winding is connected to the bottom of the
6.1 volt winding.  The bottom of this winding is connected to terminal A.

The fourth winding is a 5.4 volt winding which is used only when you press the Whistle button.
This winding is not relevant to this discussion.  

Looking at these windings from top to bottom, terminal A is the common terminal.
Terminal B provides an unprotected 2.8 volts from the 2.8 volt winding, terminal C provides an
unprotected 8.9 volts from the 2.8 volt winding connected in series with the 6.1 volt winding,
terminal D provides 18.8 volts from the 2.8 volt winding, the 6.1 volt winding, the circuit breaker,
and the 9.9 volt winding all connected in series, and terminal U provides between 9.9 and 18.8 volts
from the 2.8 volt winding, the 6.1 volt winding, the circuit breaker, and a portion of the 9.9 volt winding
(selected by the position of the slider) all connected in series.

Looking at these windings from bottom to top, terminal D is the common terminal.
Terminal A provides 18.8 volts from the 9.9 volt winding, the circuit breaker,  the 6.1 volt winding,
and the 2.8 volt winding all connected in series, terminal B provides 16 volts from the 9.9 volt winding,
the circuit breaker, and the 6.1 volt winding connected in series, terminal C provides 9.9 volts
from the 9.9 volt winding and the circuit breaker connected in series, and terminal U provides
between 0 and 9.9 volts (not protected by the circuit breaker) from a portion of the 9.9 volt winding
(selected by the position of the slider).

In the Accessory Power Box, Common (black) is connected to terminal D on all three transformers,
Siding Power is connected to terminal A (18.8 volts) on the first transformer, Turnout Power (green)
is connected to Terminal B (16 volts) on the second transformer, Accessory Power 1 (gray) is connected to 
Terminal B (16 volts) on the third transformer, and Accessory Power 2 (blue) is connected to Terminal C
(9.9 volts) on the third transformer.

I believe this maintains the integrity of the common connections, provides fixed voltages for all
accessory circuits (eliminating the possibility of someone accidentally changing the voltage by
moving the control handle on one of the transformers), provides circuit breaker protection for all circuits, and 
isolates the functionality to individual transformers (the first transformer provides Siding Power, the second
transformer provides Turnout Power, and the third transformer provides Accessory Power).


Ira