It will divert a larger load through the diode producing a stronger DC signal and more of the compensating voltage to the track. It may have been done to keep a sluggish whistle tender working more consistently.

Are you sure you have read the rating of the resistor properly? Check that is isn't rated @1.0 ohm and not 10 ohms...  Or did you open it up because it didn't seem to work correctly?  --Frank

PS--Perhaps it was used for running or controlling something other than trains?

Frank you are correct!

It is a 1 ohm resistor!

So the resistor would amplify the DC signal going to the track?

The diode goes directly in series with the power on the first contact of the whistle switch, then is shunted by the resistor at the second contact.  The resistor is providing a higher resistance path for the shunt and thus providing more DC to the track at the fill lever travel.

So I take it, this is a good thing and should leave it in there?

I plan on using this transformer on my test bench as I like playing around with pre and post war trains!

My understanding was that Lionel planned for an extra voltage added to compensate for the power draw of extra motor of the whistle running.  This way the locomotive would not slow down when the whistle button was pushed.  Not sure about the 1033 transformer but I do know that the separate whistle/reverse controllers had a resister in the circuit which would actually lower the voltage coming from the transformer during normal operation.  When you hit the whistle button two things happened:  You got the surge of DC power over the AC and the resister was cut out giving a higher voltage to the track.  You can see that if you push the whistle button when you don't have an engine on the track but have a lighted car.  That car light gets brighter while you're holding down the whistle button.

Paul Fischer

The 1033 has a 5 volt compensating winding as referenced in my earlier post.

quote:

Not sure about the 1033 transformer but I do know that the separate whistle/reverse controllers had a resister in the circuit which would actually lower the voltage coming from the transformer during normal operation. 

I believe they used a choke, as opposed to a resistor, to drop the voltage during normal operation.

Virtually all the PW transformers with a whistle control had the compensating winding that Rob mentions.  It was switched in when you activated the whistle control.  First step was through the rectifier, the second step (lever pushed farther) was to add the parallel resistor to drop the DC voltage to the relay holding level and to boost the track voltage to compensate for the AC whistle motor.  When you look at the whistle control, there are two contacts that correspond to the two step operation of the whistle control.

The resistor was a bypass to prevent full current passing through the rectifier disk and damaging it.  The PW repair manual discuss the effect of a lower or higher resistance to the effect on the voltage drop across the rectifier disk.  The addition of the 1 ohm resistor would have increased the holding voltage for the whistle.

Since this was switched to a modern Diode (if it is rated correctly) I thought folks were removing the bypass resistor when a diode was used. G