Some wheels are shorting (sparking) on an Atlas 7.5 switch. I added a PSX-AC breaker. It doesn't trip. But, can the DCS signal drivers still be damaged? Should I correct this switch issue before damaging my TIU.
There are many scenarios where electrical mishaps can cause problems with the TIU DCS output drivers, and in extreme situations my hunch is sparking is one of them. However, the sparking you see when crossing over switches is not necessarily shorting. This could be typical electrical arcing that happens when loads disconnect and reconnect while energized.
This isn’t to say that the behavior is 100% harmless, but it’s probably not the end of the world either. I would recommend cleaning the track, rollers, and wheels with some DeoxIt D5 and see how that goes.
Does this fall within the scope of what can be protected against with a TVS?
To an extent, yes. However as Adrian’s posts have shown us, the TVS devices need to be within an inch or less of what they are protecting to be effective in these situations. This means inside the TIU and locomotives. This is not to say that a TVS on the transformer output or connected to the track lock-ons is useless. They will offer some protection in certain cases.
Also, so as not to anger the train gods that lurk here, this isn’t to say that having TVS devices is 100% necessary, nor are they a total panacea to DCS signal degradation. Quite the opposite in fact. As GRJ has told us, a 0.22 mH choke is a good idea when you are using multiple TVS devices per circuit.