I powered up my layout last night to run some trains and my inner loop tripped the breaker. Checked the track with a meter, all good. Put the train on one car at a time, no short on the meter. Powered up and tripped the breaker. Disconnected from var 2 and switched to fixed 2 and all is good again. Looks like a have a bad var 2, I use the var channels to run my conventional loco with the handheld remote. Question is, is this an expensive repair?
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You could always take off the TIU cover and apply about 10 volts to that channel. Touch the diode. You'll know right away if it is or isn't the problem. If its hot, The diode needs replaced. I had a very similar experience not too long ago 
Yep, it's clearly the top suspect, though the driver FET's could have died as well.
It's a nice big axial lead part, about the size of a 1 watt resistor. 
Think I can handle that LOL!
The output side of var 2 is shorted, the input side is not. Looks like I need to find a replacement diode.
Did you to the experiment with low voltage to see if the diode starts to heat up?
Just used the multimeter on it.
Well, we know the output is shorted, the object of the exercise was to see if the TVS gets hot.
I haven't gotten around to dismounting my TIU to open it up and check.
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