FUSES IN THE GROUNDS IN THE TIU

Fuses can be anywhere in the circuit and be effective.

The problem is if all the grounds are connect with a blown fuse the TIU will still work, even the channel with the blown fuse.

thank you MONK

The circuitry, including the grounds, are isolated for each channel.  When you connect the grounds externally, the power still has to flow through the entire internal path of each channel to complete the circuit.

When you blow a fuse on the TIU with all the grounds common, that channel ceases to provide power, so clearly this is not an issue with the TIU and the position of the fuses.

The problem is it dos not quit working with the grounds connected.

than you Monk

The channel with the blown fuse will drop off line. The other channels will still be on line because they have not sustained an overload. That’s how it is supposed to work.

james g lucas posted:

 The problem is it dos not quit working with the grounds connected.

What he said.   The channel with the blown fuse will drop off, it will no longer deliver power.  The channels with good fuses will continue to operate normally.  I'd be upset if it worked any other way! 

Do you really want all the channels to die if one fuse was blown?

I think he is saying the channel with the blown fuse still works. There must be a backfeed somewhere on the layout.

If a channel with a blown fuse still works, then the hot sides of multiple channels are connected together somewhere. And that’s not good.

I imagine channels are not fed by independent power sources but rather one transformer?  With common ground, the hot of that channel will return to transformer via the common ground, hence his dilemma? No?  G

It looks like Iam having a problem getting  across my problem to you all. Down stairs on my big lay out with the TIU with a blown fuse in #1 constant ch (that I did not know about) it all worked fine. With a Z-4000 on #1 & #2 constant ch's & Z-1000's on the the other two ch's. All the grounds connected,everything worked fine. Then I brought the TIU up stairs & connected it to another loop. Using a Z-1000 on constant ch #1. It wouldn't work until I tied grounds together. That is when Gunrunner I think, told me I  had a blown fuse, & I did. I replaced it & everything was fine. It looks like that the fuses are in the grounds, why? Others have ask the question about the fuses in the grounds & not gotten an answer.

thank you MONK

Try this:

Disconnect everything from the TIU that had the blown fuse. Re-install the bad fuse in the channel that it was found in originally. theIf you no longer have the bad fuse completely remove that fuse from the TIU (no fuse being the same as a bad or open fuse).

Re-connect power to the input of only the channel with the bad fuse (or no fuse). Measure the voltage at the output of that channel.

You should read no voltage. This would mean, as stated above, you have a back feed somewhere between TIU channels on your layout. Or possibly other problem with your TIU? I'll leave that to the qualified MTH techs here on the forum (which I am not one of).

If you power all four channels with one transformer and then tie the grounds together then no, a blown fuse will NOT shut off power to that block. This is because, although INSIDE the TIU each channel is electrically separate, by using one power source IT ties all four channels together electrically on the input side so the block ground wire for the blown-fuse TIU SEES ground looking back through the other TIU channels.

Agreed, that it was a dumb idea electrical-engineering-wise to put the fuses on the ground side but the only person who could answer "why" is the person/team that designed the thing. 

james g lucas posted:

It looks like Iam having a problem getting  across my problem to you all...

 

As Lew states above, it depends on whether your grounds are tied together on the input side or the output side...or some combination of both.  As shown in the somewhat simplistic diagram above, consider the case of the fuse on the 2nd channel is blown.  In the left case (grounds on input tied), the blown fuse means no output power to the 2nd channel.  But in the right case (grounds on the output tied), the blown fuse is ineffective in that the 2nd channel picks up the ground from one of the other channels.

I wouldn't go so far as calling this configuration "dumb" though.  That is, there are 2 types of "hot" or red-jack circuits in the TIU.  The variable channels have a rather complex circuit that can chop the incoming sinewave.  The fixed channels have a DCS filter which looks like a DC-short if measured with a meter, but it is nevertheless a circuit rather than a solid electrically ideal piece of wire.  Without getting into arcane techno-babble it is not a case of my-way or the high-way.  If you have a spare rainy afternoon with nothing else to do, go thru ALL the configurations of the TIU, such as externally powering the TIU via the AUX PWR input, and follow the ground connections to decide if fusing is better on the "hot" side or the "ground" side.  I yield the soap box.

Stan, your pictures are worth at least a thousand words, maybe more!

Of course, lost in all this fuse discussion is the fact that if you're blowing the 20A fuse in the TIU, you have a serious issue somewhere with either your power or your layout!  Your circuit protection should be kicking in before you zap that fuse.  My PH180 transformers have tripped lots of times for various derailments and the like, but the TIU fuses live on.

Thank you Stan that is what I have been looking for! Everyone else I don't know why the fuse was blown this TIU is on lone to me, I don't think I did any thing wrong & its working fine now and everything is the same.

thanks you all MONK

gunrunnerjohn posted:

Of course, lost in all this fuse discussion is the fact that if you're blowing the 20A fuse in the TIU, you have a serious issue somewhere with either your power or your layout!  Your circuit protection should be kicking in before you zap that fuse.  My PH180 transformers have tripped lots of times for various derailments and the like, but the TIU fuses live on.

That's it! That's what has been niggling at me. I kept wondering why the super-breaker in the PH180 hadn't protected the TIU fuse because doesn't the PH180 trip at 10A?

Explain to me why it is off in the left diagram?  Usually track ground is not isolated between loops in a layout if they are connected.  Separated, I get it.  G

you're kidding right?

https://ogrforum.com/topic/blown-fuse

I have the commons of Fixed 1 & Fixed 2 In and Fixed 1 & Fixed 2 Out tied together with common ground wiring on my layout. If there is only power on Fixed 1 the track Fixed 2 is attached to does not have any power. It seems like you have a layout wiring issue or the hot lead of Fixed 1 is connected to another hot lead somewhere.  

Lou1985 posted:

I have the commons of Fixed 1 & Fixed 2 In and Fixed 1 & Fixed 2 Out tied together with common ground wiring on my layout. If there is only power on Fixed 1 the track Fixed 2 is attached to does not have any power. It seems like you have a layout wiring issue or the hot lead of Fixed 1 is connected to another hot lead somewhere.  

I tried to say that a long time ago, but nobody was listening.

 Yes, but you don't have a blown fuse. The fuses are in the grounds that is the problem.

thank you MONK

I pulled the fuse, that should look a lot like a blown fuse.

I would submit that on the average multi-channel layout, all of the track output grounds (blacks) are tied together anyway, albeit not right at the TIU, because all outer rails are normally electrically connected.

On my layout, none of the 8 black input terminals are connected to anything--no wires to them.