The Rev. L TIU has TVS protection on all the outputs, or at least that's what I've been told.  I suspect earlier versions may not all have TVS protection on the outputs.

I have a TVS on the input power to the TIU, and also whenever I open a locomotive, I install a TVS directly across the track pickups.  IMO, that's the best place for the protection, obviously if you have a lot of locomotives it's also a lot of work.

Truthfully, I can't see where your ZW would take out boards with voltage spikes, certainly not if it was going through the TIU and a TVS. 

As regards DCS systems, it is my understanding that the TIU is TVS equipped. 

As regards using a postwar ZW and Conventional or TMCC, see photo below: fuzzy photo but shows TVS wired between "U" and "A" binding posts. Mouser 1.5KE36 CA .  

I'm just curious. It would seem that if it couldn't hurt put them everyware. What happens when this thing goes bad? My experience is that they usually selfdestruct with a bang and small explosion resulting in a short. This still protects the circuit but can make a mess depending on where it is located.

Al

When a TVS fails, normally it simply fades silently into the night.  If it experiences a huge high current spike, it can actual explode as you mention.  However, any instance of a spike that large has doubtless done far more damage than the little bits of TVS flying around.

I'd also note that if you have them on the power outputs, and around the track feeds, those are likely the ones that will see the power surge first.  The locomotives are very unlikely to randomly generate power surges.

Seems like this place sells a device with 4 TVS's and comes with a fast blow fuse block that fits 4 fuses. http://www.scottsodds-n-ends.c...-surge_arrestors.htm M thinking of getting one of these because it seems like it would be reliablesinceits isolated. 

Well, for the price, you can buy about 100 TVS diodes, but if that appeals to you, it'll work.   Note the 100 piece price, just over 48 cents.

1.5KE36CA TVS From Digikey

How does one know when a TVS goes bad?

thanks - walt

What kind of tos do I need and where do I get them?

The unfortunate fact is, unless you have a major surge that cracks/shatters the component, there is no way to know.  Obviously, you could test them in the right environment, but that would take specialized equipment.

TOS?  Do you mean TVS?  Did you click on my link in the previous post?

1.  We should distinguish between a TVS and a MOV.  A MOV can undergo gradual degradation of the many small junctions between the grains of the MOV device.  A TVS is like two back-to-back Zener diodes.  The junctions do not degrade.  If they are grossly overheated, the junction will fuse and short, or the heating due to the surge will cause the package to explode.

2.  My analysis of a Scott's TVS assembly a few years ago indicated that it was really not appropriate for our train applications.  Save some money and just buy a stock of TVS units from Mouser.  You can also add a fuse sized for the wire you are protecting.

I have seen a bad TVS with no outside damage it can happen.  This one happened to fail open, however they usually fail shorted.  Could have been a manufacturing defect, I can't say.  I've seen many failed MOV units, and quite a number of them failed in a fairly spectacular way!  They are used in many power line surge protection units, including the whole-house boxes. I recently had a friend call me and tell me his whole house unit "exploded" when he noticed that the breaker for it was tripped after a storm.  The explosion happened when he reset the breaker, probably already underway before.  I went over to assist, and the MOV array inside was mostly totally blown away!  He said he saw a bright flash around the side of the cover, I don't doubt it.

Dale is correct that a TVS is not like an MOV that gradually degrades.  Normally, the TVS will simply be dead if it's going to die.  The MOV will take a larger surge than a TVS, and it's a softer rolloff in the amplitude of the spike than the TVS as well.

I looked around and here's a good read on the difference between MOV and TVS devices.  Selecting Protection Devices: TVS Diodes vs. Metal-Oxide Varistors

Thanks Gumrunner I found the link. anybody have a diagram for wiring a TVS? Are the more tTVS diodes there are the better the protection? Can I have some coming from the transform,er to TIU then TIU to track so 4 from the transformer and 4 from the TIU? This is much appreciated 

You just wire the TVS right across the power feeding the device to be protected.  If you have several in parallel along the run, that won't hurt anything.  What you describe is not a problem.

Thanks Jon is there a link to a good fast blow fuse on the site. I see you can buy the TVS's at a discount so instead of going to radio shack and keep on buying fuses I'd rather just buy a bunch at a discount price delivered to my door online.

Note that a TVS is NOT a fuse, they serve totally different functions!

A fuse is circuit overload protection, a TVS is circuit high-voltage transient spike protection.  For full coverage, you need both somewhere in the power circuit.

Okay - you forced me to have to ask a question: Once you have the TVS installed, and it does not "explode", how does one know that it is no longer doing it's job of  "Spike" protection?  As Dale says, it shorts so you must remove all trains/circuits on that leg of the transformer; or if, the TVS is in a locomotive, must all locomotives be removed until just the one causes a short ??? A little guidance here would be helpful so as not to be fooled that the TVS is still doing the job it was installed to do.  Thanks, Dennis M.

If it fails shorted, which is supposedly the normal failure mode, you'll know.   If it fails open, you'll never know.

As far as finding it, you'd remove any locomotives on the failing power district until the short goes away.  If all are off and it doesn't go away, it's probably the one on the power drop(s).

If you've used circuit breakers, all you're out is a little time tracking it down.  If you use fuses, I suggest you pick up an extra box of them.

gunrunnerjohn:  Alright, Thank you for posting. I thought as much, but wanted someothere more knowledgable person to confirm it for me. Dennis M.

for those of you familiar with this device, what's the odds of a failure?  I suspect the answer will be "VERY low".  But I was thinking, if I use these on my Christmas layout then at least 4 or 5 will under a 4'x14' plateau that I always create in one shape or another. 

If one failed short under it It'd be nearly impossible, short of tearing down the plateau, to reach them to find which one shorted.  Until I mentally resolve this I am hesitant to use them.

thanks - walt

Well, if you're worried about the possibility of a failure, my advice would be to make them more accessible.  You could always equip the locomotives with them, and then put them on the power feed.  Is there any reason you would bury them under the layout?

gunner: Run DCS and use Star Wiring.  I put 8 terminal blocks (4 + and 4 -) under the elevated plateau to hide them.  Plus, it's more centrally located to lockon placements than having them near the transformers.

Not only that, but I try to hide as many lockons as possible too, so I usually land up with 4 to 6 lockons under the elevated plateau. 

I close off the opening with portals, hills, flats, etc.  I can remove them if need be but can't reach the whole 4' back if needed.

Depends on the reliability of the product if I use them or not.

thanks - walt

Well, they're very reliable, the only ones I've seen fail are with lightning strikes, or at least that was the report I got.  One failed open, which was an oddity.  If it makes you feel any better, they are regularly used in military/commercial avionics for circuit protection, and they can't have those crapping out all the time.

Gunner, do you actually put the TVS right on the roller?  The wire doesn't wear thin with the roller turning or stop the roller from turning?

Thank You

Ken

No, just on the connection from the roller.  Just electrically connected to the roller.

So the shell has to be off?  Do you have a picture showing what you did?

THank You

Ken

Yes, the shell has to be off, I just find the hot wire from the rollers and connect between that and the wheel (frame) connection with the TVS.

I don't happen to have a picture, but every locomotive is different.  Most of mine are TMCC and the wires come up to a wire nut, so it's pretty easy to add in the TVS.

First off my electrical knowledge is very limited. I seemed to be going through Lionel smoke units and ac regulators at rate of every three weeks. I took Gunrunners advice and started placing on each engine. Very cheap and easy to do. I don't know why I have had so many smoke issues but if this helps at all I see no reason not to try it. 

I don't know why the smoke regulators are going that fast, there must be something in the air.   The smoke units don't have much besides the motor and the resistor.  I've had a few bad motors, but to date I've never had a resistor fail.  I've had a couple that got so corroded with burnt wick that I replaced them, but they would still function.

Lionel service has repaired 8 smoke related problems for me in last 7 months. I have explained to them my wiring and breakers and they say all is fine. They felt confident I was not the cause of the problems. I feel I must be involved somehow because thats way too many. They have replaced AC regulators, vision control boards, several motors, wicking, resistors and more. I can email you the repair reports if you felt you had time to look them over to see if you can determine something I am doing wrong. Lionel service is great but it keeps happening. 

Jeff,

If the boys at Lionel can't figure it out, I doubt looking at the repair reports will do much for me.

That is a LOT of smoke unit problems!  Have you had other issues with different stuff as well, or do you just kill smoke units?

No other issues whatsoever. I even run Proto Sound 2 and Proto Sound 3 smoking engines with zero problems, also a bunch of K-line wireless control dump cars. All accessories, switches and lighting are powered seperately. 

Gunrunner, I must admit I am a huge smoke fan user, even on diesels, just love it. I run my layout about 2 hours a day, smokers on high. If a Legacy is sitting I make sure smoke is powered off. They are used fairly hard;if it matters. 

Well Jeff, I suppose it does matter, since they keep crapping out!   I use the smoke at times, but I don't use it continuously, too many complaints from the peanut gallery.

Thanks - I feel confident enough to use them now.

- walt

Walt, I doubt you'll have a problem, but I don't guarantee it.   I've never personally had one fail, but I have gotten a couple of repairs that they were dead in.  I have no way of knowing what abuse they suffered before they died.

John or anyone else knowledgeable in this subject?

Could you wire a circuit breaker first,that would protect the TVS,then install the TVS,then install another circuit breaker.That way you would maybe know,if you had a real problem,because then the circuit breaker would pop,before the TVS has an issue,and therefore you would know if the TVS could  possibly had been damaged.

I am very limited in my understanding of this subject,so if its a ridiculous question,my apologizes.

Thanks Bryan