Melting TIU Aux Power plugs!

What are you powering the TIU with?

I tried powering the TIU with the 18v plug from my Z-1000 - whose 14V terminals were powering my accessories - and found the plug/wire instantly getting VERY hot.

I changed to a dedicated wall-wart and don't have the problem anymore. I suspect there can be problems powering the TIU with an aux transformer that shares a common with track power, but I can't verify that.

If you have an ammeter you might check to see how much current is flowing into the aux port.

What are using to power the AUX IN with? Sounds like you are overpowering it actually.

I am using the 20-volt output of a KW to power the TIU’s until I change to individual 18-v transformers for each TIU. The KW is about 100 feet from TIU-1 and 60 feet from TIU-2, and I am using 14-AWG wire. The KW, and eventually 18-volt transformers, is at the control center so I can turn both TIU’s on/off easily.

Here are some facts that just caught my attention (just measured it):
• Voltage at the KW 20-volt posts, with both TIU’s connected, is 13.8 volts!

• Voltage at these posts with only TIU-2 connected is 19.2 volts. Voltage at the unplugged TIU-1 plug also is 19.2 volts, as would be expected.

• Could not measure the true open voltage because I cannot remove the plug from TIU-2!
Earlier, I thought that this plug was fine, but it is not; it also looks partially melted. This plug is a factory wired plug.

So it appears that TIU-2 does not load down the KW’s 20-volt output very much as it still measures 19.2 with only TIU-2 powered up.

But when TIU-1 is connected, the drastic drop to 13.8 volts at the KW posts makes me think that something abnormal is happening at TIU-1.

Your thoughts?

Thx

Alex

quote:

I am using the 20-volt output of a KW to power the TIU’s

A Post War KW? Are you using the D - U posts to power the TIU AUX PWR plugs? What else does this KW power? Does the U post connect to the center of the AUX PWR plug on both TIUs?

quote:

the drastic drop to 13.8 volts at the KW posts makes me think that something abnormal is happening at TIU-1.

Agreed.

Have you checked the phasing of the KW with the track power transformers? When you plug into the Aux Power input only one wire trace from Fixed Channel 1 is broken. The other (common) stays connected. If the two transformers are out of phase it could cause a problem even if the KW is otherwise isolated.

The other thing to look at is the jack. Make sure the center prong jumper gets fully disconnected when you insert the Aux Power plug.

Gary,

“A Post War KW?”
Yes.

“ Are you using the D - U posts to power the TIU AUX PWR plugs?”
Yes

“ What else does this KW power?”
Only the TIU’s and the switch-tracks, which is an infrequent and momentary draw, of course. For the switch-tracks I will be using a separate transformer hopefully today or in a few days, and eventually a CDU.

“Does the U post connect to the center of the AUX PWR plug on both TIUs?”
That is the case with TIU-1 for sure, and I can’t quite tell right now about TIU-2, but I think so. See below under ‘more facts’.

Dave,

”Have you checked the phasing of the KW with the track power transformers?”
No. Since the track is not connected to the KW, I didn’t think it would be necessary.

”When you plug into the Aux Power input only one wire trace from Fixed Channel 1 is broken. The other (common) stays connected. If the two transformers are out of phase it could cause a problem even if the KW is otherwise isolated.”
Oops, no wonder. Please see below under “Other Transformers and Wall Warts.”

”The other thing to look at is the jack. Make sure the center prong jumper gets fully disconnected when you insert the Aux Power plug.”
I will, later this afternoon.

OTHER FACTS:

When I first set the system up, I attempted to power both TIU’s with one of the Z4K’s 14-V output. I made sure that both TIU’s were connected the same; that is, both plug center connections together, and powered them with the Z4K.

Immediately, the Z4K breaker tripped. I thought I must have mixed up the wires to the TIU plugs so I reversed the connections. Same result – tripped OL. So I swapped the wires as they were connected to the Z4K, and still had the OL problem. Then I swapped Z4K’s but results were the same.

To make a long story short, either of the Z4K's could power a single TIU fine, but as soon as I added the second TIU, regardless of how the TIU’s were connected together, or to which Z4K posts, the OL was tripped. So I went the KW and had no problems – or at least that's what I thought.

OTHER TRANSFORMERS or WALL WARTS
I suspect that using separate transformers or wall warts gets around the phasing problem as I have not read or heard of this problem before. Is this correct?

I am headed out now (benefits of retirement!) to find the transformers (need to buy several) and other electronic stuff. If I can’t find these at Gateway Electronics (St. Louis) I will order them from Jameco this afternoon.

Thanks Guys!!!

Alex

quote:

When I first set the system up, I attempted to power both TIU’s with one of the Z4K’s 14-V output. I made sure that both TIU’s were connected the same; that is, both plug center connections together, and powered them with the Z4K.

Immediately, the Z4K breaker tripped. I thought I must have mixed up the wires to the TIU plugs so I reversed the connections. Same result – tripped OL. So I swapped the wires as they were connected to the Z4K, and still had the OL problem. Then I swapped Z4K’s but results were the same.

Alex;
It sure sounds like something is wired wrong here.
I power my single TIU from the Z4000 14 VAC taps, and it works fine. The 14 VAC supply CB is 4 amp, so there is no way two TIU's should pop it. MTH says provide a 1 amp power supply to the TIU. My own experience has been that they don't draw more than 500 ma at around 14 VAC.
It would be handy if you had an AC ammeter so you could check the current draw. This would maybe shed some light on the problem. It sounds like each of your TIU's is drawing in excess of 2 amps for some reason.
Also from my experience there is no need to power a TIU with more than 14 VAC or VDC. They don't work any differently with higher voltage.

If you have a composite wiring plan for your layout I suggest checking it for wiring conflicts. It's possible that you may inadvertently have something out of phase, or something hot connected to the common return wiring, or some such thing. It's not always easy to predict conflicts unless you study the master wiring diagram closely.

What is your main TIU track power voltage? 18 volts? You should not run any lower for DCS or TMCC.

Just my thoughts.
Rod

quote:

“ What else does this KW power?”
Only the TIU’s and the switch-tracks, which is an infrequent and momentary draw, of course.

Do your switch tracks have non-derailing?? If so, then phasing is important.

You should be able to power both TIUs with a Z4000 14v accessary output, but phasing is important. The black terminal must be connected to the center of the barrel plugs.

I've been using this approach since day one and in my situation it is very convenient. It cuts down on wiring and the TIUs get power when I turn on the Z4000 main rocker switch, prior to applying track power. Works for me, your mileage may vary.

If you are having a problem powering the 2 TIU together without any other wiring hooked to the transformer, there is a possibility the wires in one of the TIU are wired backwards causing an out of phase problem. You see it on transformers every now and then.

Since Alex states the problem doesn't exist using just one of either TIU, I believe this may be the case.

Well, my fault – aux power plugs were out-of-phase .

The wires were marked correctly, but the factory markings of the factory-made harness I used for TIU-2 was reverse of what the other was, and I did not check it out when I installed it several months ago. Afterwards, when I made my own harnesses, I kept using the same polarity, so the problem persisted. Somehow the trains ran mostly OK, but who knows if this was the source of some of the intermittent DCS problems I have experienced.

How I found out, and then confirmed by using a long wire to reach each TIU location and the control center to check for continuity.

I finally was able to wiggle the TIU-2 aux power plug out, and then tested each TIU by itself. Each TIU alone did not cause any voltage drop on the KW, whether using the 20-V (19.5-V) or the 14-V (12.6-V) posts.

I connected the TIU’s together, as they had been, to the KW 14-V posts and added a 0-3 AC ammeter in series. When I turned the power ON, the meter went pegsville! (Anyone here ever used this term?) I repeated the test again with each TIU individually, and the meter went up about to 1 amp and then back to zero. I thought the meter had been damaged.

After correcting the polarity problem (new plug for TIU-2, so now both have new plugs and these are certified to be in phase ) I connected them to the 14-V KW posts, and voila!, the voltage did not drop from the open circuit reading of about 12.6 volts. I measured the current using the ammeter I had used earlier, and it read about 0.4 amps. Keep in mind that this is with only the TIU’s powered up, not the tracks, and I suspect that the TIU’s current draw may increase when they start ‘working’. Is this correct?

This still does not explain why I had the problems with the 4K's months ago, and I know that back then I tried reversing polarity and still had problems. However, I did not pay attention to which post I connected the TIU's as Gary stated that I should. I have not yet tested this using the Z4K's 14-V this time, but I will. I do want to keep the Z4K 14-V just for accessories, and will power the TIU's separately.

Thanks for your help!

Alex

quote:

I suspect that the TIU’s current draw may increase when they start ‘working’. Is this correct?

In my experience it makes no difference at all.
The track power is after all supplied totally independently.
Glad you resolved your polarity problem!

Rod