Does anyone know if the new TIU's have TVS's installed internally? Always a question about where they should be installed, between transformer and TIU, or TIU and tracks. Thanks for any input.
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Don,
There's one TVS per TIU channel in all TIUs.
John,
I do believe that they are on the output side. How does this affect the variable channels and not the fixed channels?
The variable channels have FET's between the input and the output, other than the relay, nothing is really between the fixed inputs and outputs.
John,
I know that, however, what's the actual defense as regards TVS operation?
If they are on the input, they'd have very limited effect through the FET controls of the variable channels. The TVS is to suppress very rapid high energy spikes, and I doubt they'd be nearly as effective through the FETs.
gunrunnerjohn,
I considered this at one time myself, however I do not beleive it is as big a problem as some might believe, I ran for over 10 years with just the Scott 10 Amp breakers,
using the internal TIU TVS safety and never ever had one problem. Now maybe I was lucky, however I really do not believe this to be the case.
PCRR/Dave
John,
If they are on the input, they'd have very limited effect through the FET controls of the variable channels
So, since the TVS's are on the output side of all 4 channels, there is no difference in their effect of the variable channel sand the fixed channels.
It might be a good idea if you removed the statement:
"Obviously, this doesn't mean much for the fixed channels, but would for the variable channels."
from your earlier post, as it is misleading.
Barry, my point of the earlier statement was that for the fixed channels, there is very little difference between the input and output location.
I'll remove it anyway, but I can't imagine if someone was following the conversation they'd be confused.
John,
I'll remove it anyway, but I can't imagine if someone was following the conversation they'd be confused.
Rest assured, I was confused! 
WOW, that begs for a shot, but I'll abstain. 
John and Barry,
Thank you very much for the information and discussion ! I found it very informative, I appreciate the service you guys provide.
A last thought. Whenever I have a derailment, my TIU shuts down, and I need to cycle the ZW controller that is providing the power. The fuses and circuit breakers I have in line are never impacted. Its as if there is a circuit breaker inside the TIU that is the most sensitive component. Its worked like this for 6 years so it must be OK.
Some Data:
TIU Rev. G
ZW Controller with 4 bricks
In-Line Cartridge Fuse (between TIU and tracks)
TVS - across output posts of TIU
Ckt Breakers, 10a fast acting, between ZW Controller and TIU
Also, the TVS's had a lead that came from them that was suppose to go to earth ground, that has been eliminated. Now there is only two leads, they look more like a diode.
Don,
Its as if there is a circuit breaker inside the TIU that is the most sensitive component.
I can assure you that a Rev. G TIU has neither a fuse nor a circuit breaker. Some other device, external to the TIU, is shutting down power.
FYI, no TIU has a circuit breaker, although all TIUs after the Rev. G have fuses on each channel.
The ZWC is probably the thing that is shutting down, or the bricks powering it. As Barry says, it's not the TIU. I previously made the same mistake of assuming the TIU had circuit protection. Other than the 20A fuses, there is no over-current protection in the TIU.
