Blown TIU

The light doesn't go out, but it's hard to believe that the transformer is responsible, I've been using them for years, and they're all I use now on my new layout.  We've used them since we started our modular train club in 2010, and we have no reason to switch.

If you had a Rev. G (the original), they didn't have internal protection fuses, and they also had an undersized internal trace that could fry with less than 10 amps, so the breaker on the PH180 would have no reason to trip.

John, thanks for responding.  You did a PS3 upgrade for me on an MTH Hudson a few years ago.  The TIU appears to be Rev I3.  I have tested it and all 4 channels seem to be dead.  I have opened the TIU and visually inspected what appear to be 4 green blade fuses and they seem intact.  I have not yet removed and tested them.  There is no apparent damage in the TIU.  That's about as far as I can go on my own I think.

I have another TIU that is Rev L but I'm afraid to hook it up without additional protection as I don't understand why the PH-180 breaker didn't protect the first TIU and I don't need to blow another one.  Any thoughts would be welcome.

You might consider using your tiu without running the power through it.  I'm blanking on the correct term for that but I'm planning on switching mine to that configuration soon to avoid the problems that can come with running full current through them.  They basically just become a radio on the power line.

@Dougklink posted:

You might consider using your tiu without running the power through it.  I'm blanking on the correct term for that but I'm planning on switching mine to that configuration soon to avoid the problems that can come with running full current through them.  They basically just become a radio on the power line.

Passive mode. The TIU is only used for DCS signal, not for controlling or passing power.

The reason for the choke or inductor in series to the transformer is- DCS is a high frequency signal. The transformer would short or attenuate the signal. The choke is high impedance (resistance) to high frequency signal like DCS so that the transformer does not attenuate it.

All TIUs and technically any DCS control system (TIU- all versions, DCS explorer, IR Commander) all have an identical choke inductor for the same reasons in series internally on the input.

Thanks Vernon.

@noswad posted:

A while back I purchased a Lionel PH-180 transformer primarily because in was recommended for having a fast breaker that would protect the layout.  One day while running a balky pre-war Lionel 226 I had a short that blew out my older TIU.  The transformer breaker provided no protection. If the PH-180 breaker trips does the light in the power switch go off?

What's up with that?  Why didn't the transformer protect me?

Are you sure that it was a current overload due to the short circuit on the track that killed your TIU?

Based on what you've recently posted, it doesn't appear that a current spike (overload) that killed it, especially since the internal fuses don't appear to be blown.  Whatever took it out, neither those fuses nor the PH-180's circuit breaker intervened.  This means to me that overcurrent wasn't the cause of the failure.

Perhaps a voltage spike instead?  Breakers and fuses aren't capable of protecting against this.  You need TVS diodes in addition.  Yes, there are some inside the TIU to protect it, but these can be quite a distance from the source of the spike, i.e. the derailed engine on the track, so many of us also put them across the power feed right at the track for extra protection.

Check out this post:

     Best places to locate TVS diodes in MTH DCS systems w/ Legacy (2/12/21) | CAPPilot

Mike

I seriously doubt that the PH180 had any hand in the TIU failure.  I suggest you have it looked at by an MTH ASC and see what really happened to it.

Mike, all I know is the 226 engine was binding up and like an idiot I just gave it more juice. Then things got really quiet.  

John, will take your advise to send to a repair shop.  Can you recommend one or two?

Thanks for all the posts.  This forum is a great place  

mf4j