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My layout in split electrically into 2 blocks that are isolated by a single insulated center rail joiner. Each block is powered by its own Lionel 180 watt powerhouse that runs through each of the 2 fixed voltage channels in my TIU. I have discovered that both the powerhouse for fixed voltage channel 2 and the fixed voltage channel 2 itself in my TIU are not operating. The isolated powerhouse for channel 2 produces no voltage on my volt meter. The input and output TIU connections for channel 2 both read zero on my meter when powered by either the seemingly failed powerhouse or a postwar set transformer. I have determined that the fuses in my TIU are fine by swapping the 2 fixed voltage channel fuses with channel one working and channel two dead, regardless of which fuse is in which slot. The only other strange symptom is that my volt meter shows 18 volts when I test the voltage between the center rail of the dead block and the live block - I did this test after an engine caused lots of sparks after it was inadvertently routed from the live block into the dead one! And no, I can’t find a short circuit in block 2.

I know that my powerhouse for channel 2 probably needs to be replaced under warranty - it’s just 1 month old. But does anyone have any idea what’s up with my TIU fixed voltage channel 2? I’m concerned that a failure with channel 2 in my TIU may have trashed my powerhouse... and could well trash a new replacement powerhouse!

Thank you for your thoughts!

Peter

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@Peter C posted:

...The isolated powerhouse for channel 2 produces no voltage on my volt meter. The input and output TIU connections for channel 2 both read zero on my meter when powered by either the seemingly failed powerhouse or a postwar set transformer.

What does meter show for continuity/Ohms between red and black Fixed In 2 jacks?  Does it indicate a short circuit?  If so perhaps your TVS protection diode inside the TIU failed (is shorted).

In which case, not sure why the Powerhouse did not protect itself and is now dead...but if your PW transformer reads normal voltage by itself but 0 Volts when attached to Fixed In 2...then it seems to me TIU Fixed 2 is internally shorted.

For a simple bench verification of a shorted-TVS you can simply clip one terminal of the corresponding TVS diode and see if the short goes away.  There have been dozens of OGR threads on managing/replacing the 50-cent TVS diodes.

MTH might have changed the placement of the TVS diodes between revisions but here's what it "might" look like...

TIU fuse and tvs

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  • TIU fuse and tvs
Last edited by stan2004

Not familiar with the OGR meter.

But unless it's some odd-ball design, do the following.  Place it in the Ohms/Continuity mode.  It doesn't matter the range...but if there is a choice use the lowest range.

Note the reading with the meter probes not touching each other.  If a numerical reading is indicated it should be some ginormous number in the millions or billions ... but more likely maybe just some dash symbols showing it's a huge number.

Then touch the two probes together simulating a short-circuit.  The numerical reading should go to zero (0) or something near zero (i.e., less than 1 or 2 Ohms).

Then put red probe on the red Fixed 2 input, black probe on black Fixed 2 input.  What does it read?  I'm betting it's some very small number indicating a short circuit.

Oh.  This is with NOTHING connected to the output of Fixed 2.

Last edited by stan2004

So when you connect your postwar transformer to fixed in 2 on the tiu, with nothing connected to the fixed 2 out, your meter reads 0 volts on both input and output of tiu fixed 2?

@stan2004 posted:

What does meter show for continuity/Ohms between red and black Fixed In 2 jacks?  Does it indicate a short circuit?  If so perhaps your TVS protection diode inside the TIU failed (is shorted).

In which case, not sure why the Powerhouse did not protect itself and is now dead...but if your PW transformer reads normal voltage by itself but 0 Volts when attached to Fixed In 2...then it seems to me TIU Fixed 2 is internally shorted.

This seems like the case... but if the TVS is a dead short, then I’d think the breaker/fuse in the postwar transformer would have popped, and or a shower of sparks and some magic smoke.  

@rplst8 posted:

So when you connect your postwar transformer to fixed in 2 on the tiu, with nothing connected to the fixed 2 out, your meter reads 0 volts on both input and output of tiu fixed 2?

This seems like the case... but if the TVS is a dead short, then I’d think the breaker/fuse in the postwar transformer would have popped, and or a shower of sparks and some magic smoke.  

Yes, meter reads 0 volts on both input and output of TIU fixed 2. And yes, my little postwar transformer became warm very quickly and started to smell hot... I immediately unplugged my transformer at this point! I’m not sure about the breaker/fuse protection in my postwar transformer since it is a very small cheap unit that came with my first 027 set in 1962.

Are you saying between the center rail of the dead, and the outside rail of the live one?

Not the center to center of the 2, right?

So power is getting thru somewhere.

Yes, I am saying between the center rail of the dead and the center rail of the live!

I’m thinking that my meter reading of 18 volts in this scenario means that my TIU fixed 2 output must be shorted out, perhaps by a failed/shorted TVS as other forum members have suggested.

@Peter C posted:

Yes, meter reads 0 volts on both input and output of TIU fixed 2. And yes, my little postwar transformer became warm very quickly and started to smell hot... I immediately unplugged my transformer at this point! I’m not sure about the breaker/fuse protection in my postwar transformer since it is a very small cheap unit that came with my first 027 set in 1962.

Ok, then I’m with the others... likely a shorted TVS.

@stan2004 posted:

Not familiar with the OGR meter.

But unless it's some odd-ball design, do the following.  Place it in the Ohms/Continuity mode.  It doesn't matter the range...but if there is a choice use the lowest range.

Note the reading with the meter probes not touching each other.  If a numerical reading is indicated it should be some ginormous number in the millions or billions ... but more likely maybe just some dash symbols showing it's a huge number.

Then touch the two probes together simulating a short-circuit.  The numerical reading should go to zero (0) or something near zero (i.e., less than 1 or 2 Ohms).

Then put red probe on the red Fixed 2 input, black probe on black Fixed 2 input.  What does it read?  I'm betting it's some very small number indicating a short circuit.

Oh.  This is with NOTHING connected to the output of Fixed 2.

Thanks @stan2004 for coaching me with testing continuity! With a randomly selected Ohms/Continuity range, the meter reads 1. when not connected to anything and .000 when the probes are touched to each other or to the fixed input 2 connections.

Do these readings indicate a short inside my TIU, possibly from a failed TVS? And could a defective Lionel 180 watt powerhouse cause the failure of the TVS inside my TIU?

@Peter C posted:

Thanks @stan2004 for coaching me with testing continuity! With a randomly selected Ohms/Continuity range, the meter reads 1. when not connected to anything and .000 when the probes are touched to each other or to the fixed input 2 connections.

Do these readings indicate a short inside my TIU, possibly from a failed TVS? And could a defective Lionel 180 watt powerhouse cause the failure of the TVS inside my TIU?

Those readings indicate a short.  

If the breaker did not trip correctly, the PowerHouse most certainly could have supplied too much current for too long and cooked something inside the TIU.  

That said, in a case like this it’s pretty hard to determine what was at fault over the Internet.

I can’t think of a scenario where a TIU could “kill” a modern transformer though.

@Peter C posted:

Thanks @stan2004 for coaching me with testing continuity! With a randomly selected Ohms/Continuity range, the meter reads 1. when not connected to anything and .000 when the probes are touched to each other or to the fixed input 2 connections.

Do these readings indicate a short inside my TIU, possibly from a failed TVS? And could a defective Lionel 180 watt powerhouse cause the failure of the TVS inside my TIU?

Yes. It appears there's a short inside the TIU on Fixed 2.  Since this all happened following a power mishap on the track, a failed TVS is a good suspect to follow.  That is, sparks/fireworks are notorious generators of large voltage spikes.  And the TVS is a protection device that is meant to block the sensitive TIU electronic components from "seeing" those large voltage spikes.

So in what I think is the likely scenario, the TVS did its job and gave its life doing so.  Sounds overly melodramatic but it is what it is.  And assuming it is in fact the TVS that failed, I don't think it was anything about the PowerHouse that caused the TVS to fail.

If the PH is under warranty then I would leave it at that.

As mentioned earlier, replacing a TVS can be a DIY project but it does require soldering.

If you want to investigate a bit further to see if you want to jump in the deep end, it is fairly straightforward to lift off the cover of the TIU by removing screws from the bottom.  That will show something like previous photo.  Do a visual inspection looking for anything egregious like blackened or charred components and the like especially in the area between the Fixed 2 input and output jacks.

Then find the 4 TVS diodes using the earlier photo as a guide (as mentioned there have been revisions to the TIU so perhaps they've moved a bit between revisions).  Even if you choose not to replace the TVS itself...and you're going to have someone else do it...I'd simply want to know and would use a diagonal cutter to clip one terminal lead of the TVS as illustrated below.  Then re-measure the continuity between the Fixed 2 power input jacks.  Did the short vanish?

TIU TVS

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  • TIU TVS
Last edited by stan2004

I find it VERY difficult to believe that a short, or pretty much anything you do at the output of the Lionel Powerhouse 180, killed the transformer.  I've been using the Lionel PH180 transformers for many years, and I've never killed one with the thousands of short circuits, cross connections, etc.  I've seen a failure of the circuit protection in one PH180 in our modular train club layout, but it was a random component failure, not the result of any abuse.

....

I've seen a failure of the circuit protection in one PH180 in our modular train club layout, but it was a random component failure, not the result of any abuse.

So the TVS failed shorted, and (possibly) took out the PH180?

Could the PH180 have taken out the TVS somehow?

This seems interesting to me. The PH180s seem to trip so fast, and for lighter reasons than anything else I have. I have inline fuses on my circuits and the breakers on the PH180 will trip first. The Z4000 for example, will keep supplying power on the same circuit for longer periods, depending on the short?

I mainly run 2 rail and haven't lost an internal TVS yet, after maybe 15 + years. I have changed out plenty of external 10 amp auto fuses using different power supplies. So I use them even on the PH180 circuits.

Last edited by Engineer-Joe

My 180 watt powerhouse is brand new... I hadn’t run any trains yet on that block until I discovered the problem. I don’t think the sparks from my engine crossing into that block caused the failure, but rather alerted me to a failure that was already present. My new powerhouse may have been defective right out of the box. If so, could a defective powerhouse burn out the TVS inside my TIU?

Thanks to everyone for your help with this problem!!!

@Peter C posted:

My 180 watt powerhouse is brand new... I hadn’t run any trains yet on that block until I discovered the problem.

You do realize that the new Powerhouse 180 requires a 3rd pin in the connector to enable power, right?  Are you sure you just aren't missing a simple interlock?



You guys will work this out for him. That, I am sure of.

Last edited by Engineer-Joe

The "dead" Powerhouse, if it's the new version that just shipped in the last couple of years, has a connector interlock that needs to be triggered in order to provide power to the output connector!

Do you know the details of this interlock?  Can the PH-to-TIU adapter cable (DIY or aftermarket) that has made the rounds on OGR be modified to work with the NEW version of the PowerHouse?

tiu

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  • tiu

You do realize that the new Powerhouse 180 requires a 3rd pin in the connector to enable power, right?  Are you sure you just aren't missing a simple interlock?

I can't imagine any failure of the PH180 that could damage your TIU.  The maximum voltage it can possibly put out is 18 volts as that's the highest voltage internally in the PH180.

Gunrunner,

The 3rd pin in the molex connector is not an issue here. Although the extra pin is no longer shipped with the 180 watt powerhouse, I did obtain them from Lionel Customer Service. They are installed in my Lionel TMCC cable sets (6-14194) which connect my powerhouses to my TIU.

I determined that my questionable powerhouse is dead by the following process:

1. I unplugged my working powerhouse and pinned TMCC cable from the fixed voltage 1 channel of my TIU. My meter read 18 volts at the spade lug end of the TMCC cable.

2. I then moved the same pinned TMCC cable to my questionable powerhouse and found no voltage with my meter.

Whether or not my powerhouse caused the failure in my TIU, this powerhouse appears to be defective right out of the box.

Although I don’t know exactly what caused my TIU failure, I’m thinking that my next steps are to get the powerhouse replaced under warranty and my TIU tested and repaired by an experienced MTH service station. Does this make sense to you?

This is a total WAG, but I’d bet the circuit breaker failed to open, overheated and failed to open circuit.  If the breaker in the PH180 was defective from the start, a dead short could have allowed a lot of current to flow through that channel of the TIU.  The TVS diodes do have a maximum forward current.  A household 20 amp circuit could supply well over 100 amps for short durations until conductor heating raised the resistance.  

But what's nothing less than confusing is on the TIU's I've seen, the four 20A fuses are in the common (black terminal) path of each input TIU channel.  And since the overwhelming majority (if not ALL) layouts have a shared/common AC "black" terminal, the common current could flow thru ANY of the 4 TIU "black" terminals depending on wiring integrity.  So, in a strictly pedagogical example, in the OP's situation of 2 TIU channels, you could have 39.9 Amps of return current evenly split between the two 20 Amp fuses... and therefore NOT blowing either TIU fuse!  Remember we are just talking here!

@stan2004 posted:

But what's nothing less than confusing is on the TIU's I've seen, the four 20A fuses are in the common (black terminal) path of each input TIU channel.  And since the overwhelming majority (if not ALL) layouts have a shared/common AC "black" terminal, the common current could flow thru ANY of the 4 TIU "black" terminals depending on wiring integrity.  So, in a strictly pedagogical example, in the OP's situation of 2 TIU channels, you could have 39.9 Amps of return current evenly split between the two 20 Amp fuses... and therefore NOT blowing either TIU fuse!  Remember we are just talking here!

Oh wow, I didn’t know that.  I know in home wiring fused neutrals are a big no-no.

Another point is the fuse in the transformer windings, I suspect that's still there for the new Powerhouse.  I know the older model Powerhouse couldn't conduct 100 amps for more than a millisecond or two, the traces on the PCB would be history if the internal fuse in the windings didn't go.  I'm just not seeing the PH180 caused a TIU issue, that seems to be a longshot.

01.  I occasionally look in on discussions on train devices plugged into the 120v house system, mainly from a concern for safety. Most here will know that only transformers plugged into wall sockets (et cetera) generally will have a UL label (both ZWs do not have one).  Certain requirements go with this or comparable label; I believe the toy transformer standard is maintained by the UL organization, which now means it is open to review every 3rd year.  Compliance with UL requirements will vary with jurisdiction involved.

02.  It is probably not well know here that the concept of the first "brick"--the Lionel 135-watt version-- was based on implementation of a fundimental change to the toy train transformer standard.  The requirement, that toy transformers have a circuit breaker capable of interrupting any current the particular transformer was capable of delivering under any connection arrangement,  was dropped without comment.

03.  I knew this meant that a system of "cascaded" protection was in place (this means the various protections were located in a series of different devices, from upstream to downstream. I opened my 135w brick, and determined it did not contain heavy short protection.  There was one supervised set of contacts.  Two failure modes would fit two particularly clear posts here at that time 20+ years ago: contacts burned open, or contacts welded closed.

04.  I recognized that the TIU did not have heavy short protection, and recommended that it needed protection for itself. I believe I was the first to recommend this, despite not actually having one.  (I'll note here that automotive fuses of the type fitted are not "fast" fuses --the fuse elements are flat, which radiate heat faster, making them slower.)

05.  I recommend that if a TUI must be powered from a Lionel "brick", the brick cord should not be altered but simply attached to the proper sized "lineside shack" containing a supervised contact (3rd rail wire) with wire attachment devices in the later versions.  This will avoid heavy shork damage to the brick; possible damage to the TUI may depend on the version.

06.  Heavy shorts are difficult to create, but i do recommend breaking any habit of checking breaker operation by shorting the 3rd rail to an outer rail using  pliers or screwdriver.  At a minimum, calibration in the breaker system may be altered over time.

07.  IMHO, I think the 180w brick is toast, altho the situation posts are not totally clear.

08. GRJ, I have an opinion on power loss in DCS signal loss.  Power is adequate up to several football field lengths (was it 3?). Signal distortion was the problem above 135 feet of track on the MTH test track (in northern D.C.).  Lacking a carrier wave, roadbed materials show a capacitance variation in the roadbed materials with the range of frequencies found in the signal.  The 175' yard lead lost signal at its far end  and being the 20th and last possible block (due more elaborate engine signups requiring a separate block, taken out of the yard lead), it could not be corrected.  I eventually realized that the light bulb trick 40' out on the yard lead would have corrected this problem.  Bulb data follows.  It gives nanohenrys, in somewhat the same range as nanofarads for the capacitance variation.  I've lost all but the bulb itself.  The farads have a divisor of 2pi, IIRC, for you calculators.  Test track Gargraves, wood ties, one rail dead (used for signal circuit--not DCS signal.)  Wood base had most cap variance, IIRC; thin crushed rock ballast at little more.  The layout was in a space 45 feet square, with a corner about 15 x 22 devoted to TMCC  engines; I think there was a provision to convert the main lines (mostly double track, some sidings) to TMCC, but cannot recall how wired---except dim memory it was all TMCC originally.

00.  END  --Frank

Hello Frank.  Greetings from Fairfax Station.  Haven't seen you post in awhile.  I am having problems following the above post.

You use the term "heavy short."  I assume you mean a sort where the limiting feature is the internal resistance of the transformer.  Not sure why it makes a difference if the short is heavy or "light."

I have  Powerhouse 180 on my layout, which has a very fast-acting resettable breaker.  Are you saying that this can't protect the circuit from a heavy short?

With all due deference to Frank's opinion, I think the PH180 has an excellent circuit breaker, and I have no issues with relying on that protection on my layout.  First off, the PCB traces on the breaker board in the PH180 will fry long before the transformer core.  I also believe the the PH180 also has a fuse link in the primary windings as well for overload protection in the case of an internal circuit failure.

I don't have to create a short with pliers or a screwdriver, I can create them in normal operation often enough to cause a breaker trip.  Also, given the design of at least the older PH180 breaker PCB, IMO there is no danger of changing it's calibration.

I have no idea what "lineside shack" Frank refers to is, but if it's the TMCC Direct Lockon, IMO that's a piece of junk.  It also kills the DCS signal, so hopefully you aren't running MTH equipment if you use one.  Finally, it's prone to false trips, I had a number of locomotives that would cause it to trip as they came past the attachment point on the track for no reason.  I got rid of all my TMCC Lockons, and I'll never consider it again.  It also automatically resets and keeps banging the power into the short, talk about a dumb way to handle it!  The reason I like the PH180 is I get to decide when power is applied again to the track.

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