For about a week I noticed that my 18 volt magic bulb was dimming on my layout. The other day I checked the track voltage and it was about 15.9 or so which seems low. So I checked the connectors from the power supply brick into the TIU and found that the plastic had melted on the Fixed Voltage IN 1 black terminal banana plug. I figured it was a loose connection and fixed it but no improvement in voltage and the terminal gets very hot to the touch. Trains are on the track but not operating. I tried three different transformers and get the same thing. Also does not appear to be track related. Next step is to open the TIU and see if the connection is loose on the inside. Right now that's all I can come up with. Poor contact resistance would cause a voltage drop and result in heat generation? Maybe a bad fuse?

Thanks for any help.

S

Original Post

Yes for sure open the tiu and make sure all connections are tight...

 

6 Screws on the bottom...  Don't leave it as is. good luck.

You are on the right track-check the internal connections at the offending binding post or all of them.

An excerpt from this thread:

"Every TIU I have opened up has had at least one nut on the binding post not tight enough. To fix this you need to get some M4-.70 nuts. Unscrew the nut on the binding post and remove the external washer and wire. Replace the nut and tighten. Then replace the wire. Next the external washer. Then the nut."

Carl

Arctic Railroad

What is important to remember is that the melting resulted from current flows that were within acceptable limits, so a circuit breaker or fuse would not have provided protection.  This is a matter that requires manual inspection, including fingertips to detect heat.

 

My initial issue Rev Gs do not have nuts.  This was a later improvement

Moonman posted:

You are on the right track-check the internal connections at the offending binding post or all of them.

An excerpt from this thread:

"Every TIU I have opened up has had at least one nut on the binding post not tight enough. To fix this you need to get some M4-.70 nuts. Unscrew the nut on the binding post and remove the external washer and wire. Replace the nut and tighten. Then replace the wire. Next the external washer. Then the nut."

That thread excerpt nailed it Carl. When I opened the case I expected the nut on the inside to be barely tight. But it felt tight enough when I checked by hand. Then I took a small wrench to tighten it. Wow, there were more than a few turns needed to get it tight to the level I thought it should be. I checked the other nuts for the other terminals. Same thing. Basically they were all loose to some extent. Now I have 18 volts and the terminal is cool to the touch during operation.

Without forum tech help my operation would have ground to a halt long ago.

Many thanks. S

Scott,

Glad to hear you found the issue.

I would follow the suggestion of the poster in that thread and double nut it with additional washer after the holidays. That will prevent the nuts from working loose again. That creates a binding post that isolates the post mounting from the wire connection.

It can be a safety issue as you can see from the club members post.

Carl

Arctic Railroad

I'm glad someone benefited from my post.  I didn't think anyone would even look at it with all the other posts in the thread talking about fuses and breakers after that TIU post melt down.

By the way, the part number for the replacement of the dual female binding post is BB5100004 and was $4.00 in 2/19/14 if you want to replace it.

After you replace a post that has melted, do a track signal test.  Wouldn't surprise me that the signal is degraded.   G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

Moonman posted:

GGG,

Scott was able to prevent melting by catching the hot wire.

Correct, it was just the external connector from the power supply. Power is from a Lionel 180 W (not sure) brick. Connected with a so-so quality adapter I got on eBay with banana plugs going to the TIU. Plastic melted on the banana plug.

So it is possible that in this particular situation there could have been an issue with the way the wire was fastened in the banana plug.  One must be careful about crimping solderless slip on or ring terminals or attaching banana plugs to wires. 

In any event, I agree that checking internal contacts is advisable.

Moonman posted:

GGG,

Scott was able to prevent melting by catching the hot wire.

I understand that, but others have replaced melted units, so just additional information.  Current flow high enough to melt the plastic on the terminal usually can burn off insulation on the various inductors.  That can kill DCS signal.  G

MTH Authorized Service Center

Authorized ERR Dealer

Lionel Independent Repair Tech

Virginia Train Collectors Member

HI

Does any one have pictures of the incorrect install and the Carl's (Moonman) modification to correct the problem?

Kris

 

A proud member of the Brotherhood of Carpet Layouts.  Permanent layout scheduled for Spring of  2019. New Home of Phoenix Train Works (Name of Layout)

 

As I understand it Kris, it wasn't an incorrect installation, but that over time, as the outside terminal knobs get turned, there are nuts inside that loosen  The fix was to install a 2nd nut to lock the first in place.

I suspect that  this problem is considerably less likely to surface over time if one uses banana plugs to connect wires to the TIU.

Barry

 

DCS Ambassador & author of The DCS Companion series of books

Train-Ca-Teers - All For O and O For All!

 

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