I purchased a 4090 off eBay recently; it arrived last night. It is intended to be part of a set I am giving a friend's children; this family is not train people, so I want them to have a trouble-free experience.
I tested the 4090 using the MPC MoPac GP-20s I also bought for the set. As a control for the test, I tested the engines first on my KW, and they run very well on it; the e-unit was very responsive to both teh throttle and the Direction button.
With the 4090, however, the e-unit had touble tripping, and the forward position failed over 60% of the time using the Direction handle. Most but not all of the failures were when I was using posts U & A (6-16 volts); it also failed sometimes when I was testing the U & B posts (0-11); U was the 3rd rail in both cases with A or B common. If the direction handle is bumped just a bit toward the whistle side, the loco slowed down and growled with dim lights.
Further, the unit smelled funny when I used the direction control--not like burning inulation but not a "happy" smell, either. The humming inside the unit was not constant but varied in tone and loudness.
I am guessing that the rectifier for the whistle control is failing; I am not sure about the direction control issue, but they seem to be connected,a nd not just because they are the same handle.
So I ask the collective wisdom of the forum for help with the diagnosis and cure.
