TIU Fried???

What happens  if you set it to fixed mode??? Menu/System/ dcs set up/ select channel/ then  FXD, it takes a second or 2 to get voltage. Yes it does appear the channel is defective.

I would think that you have the MAX VOLTS set too low:

TR

Select variable channel

S5 Softkey    >

S2 Softkey    MTV

Select MAX VOLTS

Roll up voltage

Press thumbwheel to set

If it is not a programming issue, it probably is a hardware fault, especially since you blew and internal 20 amp fuse.  I can fix this if you need.  The Power FETs need to eb checked and the shorted one replaced.  G

I won't hold you to anything. But what is your best guess, based on problem and what you think may need to be replaced, on cost to repair. I am almost ready to fix it with a ball peen hammer, (MY BIG ONE).

Well it's totally unresponsive to anything. Set fixed or variable voltage stays the same. It did drop to about 3.8 volts. So I'm pretty sure that channel is fried. Big decision now is to repair it or not. And of course I just decided to purchase another PS3 engine. I'm really about ready to have a fire sale. And the remote is goofy half the time you get out of range error msg, even with the remote 18" from the TIU. I did reseat the board in the TIU, but not the one in the remote. I guess I would consider this experiment a failure. I just don't know when to give up. But I'm pretty sure I won't buy another TIU eithe fix this one or  toss the whole mess. I don't know how they could take something as simple as an electric toy train and screw it up with electronics. And more, how did I let myself get sucked into this. Because the way I see it, the cool factor does not outweigh the aggravation factor.

Charlie,

Sorry to hear your having such a time. My experience with DCS has been 180 out. Everything has been working as advertised without issue. I have had blown fuses, but my system has never been flakey. I would give MTH a call and have them troubleshoot the TIU. Sounds like you might be experiencing multiple issues. Good luck.

Charlie, I sent you an e-mail.  Does Fixed 1 or 2 work?  How about Var 2?  Remember you need to power fixed 1 or use aux port.  G

I sent you a reply. Not sure if I included it but, fixed 1 & 2 and var 1 all seam to function properly. Var 2 is the dead channel. Powered with a Z750 21.5 volts in and aprox 3.8 out no mater if set for var or fixed. Voltage setting via thumb wheel has no affect on output. With remote set at 0, 3.8 out, with set at 22, 3.8 out. I hadn't hooked up var 2 until today, guess I didn't get such a deal after all. But I should have checked it completly when I got it. The seller is not going to be of any help. Thanks for your help though. I'm sure I'll send it to you at some point for repair. Thanks again

Sounds like one or more of the power FETs that control the VAR1 Output.  G

Should be a fairly simple repair.

The problem with this repair is there are 4 FETs in parallel.  So you have to remove one and test trying to find the bad FET or FETs.  So repair can vary.  G

I just replace the lot, for the cost of the parts it's not worth the extra effort of trying to determine which one is bad.

Gentlemen,

   After the repair is completed I recommend a set of 10 Amp breakers before the complete TIU, I have been running in this manner not just with my older ZW & KW's but with all my transformers, and I have never blown an internal TIU fuse.  IMO it's the only real way to completely safe guard the DCS.

PCRR/Dave

Is this a common problem? Does a FET go bad and cause the short that blows fuse? Or is it a short on the output that blows the FET? The 10amp breakers are a good idea, but if that's the case the fuses in the TIU are too large. Maybe 10amp fuses would be a better choice, or 15amp. The Z750's have 4amp circuit breakers so I feel almost certain that it was bad when I got it. And I never tripped that 4 amp circuit breaker. It's what I get for being  cheap. Because unless the FET shorted and blew the fuse, the fuse is worthless. Bout the same as putting a penny under a screw in fuse. But it wouldn't be the first time I saw overprotected, over rated, under designed, products. 25 years ago a relay rated at 15 amps had contacts the size of a pencil eraser. Now a 15 amp relay has contacts the size of a dull pencil point. You will never convince me both are rated at 15 amps. Now the older one was probably under rated. The new ones under lab conditions, on paper somewhere will handle 15 amps for 3 millaseconds so they rate it as such. Disclaimer, I'm not an electrical engineer, don't know how they get the rating, I just know that the replacement does not have the same real rating as the one it is replacing.

It's not common, and I imagine you can have a fault either way, but I think most casualties occur when a short occurs and you get high current draw, and possibly a high voltage spike when the fuse blows.  There is a TVS to suppress voltage spike.  Overload of the FET can cause the casualty.  20amp fuse inside the TIU is to protect TIU traces.  You need a 10amp at the power source to protect components.   G

Charlie,

If you bought this used, it was probably damaged before you received it. I and none of my friends have had no problems with the TIU that we have. Of course we use mostly MTH Z-4000 transformers. A PW ZW in use has the 10 amp fuse installed between the transformer and TIU as the breakers on these old transformers are way too slow to trip.

The Z750 bricks I am using have fast acting 4 amp breakers. That being said I see 10 amp fuses overkill. 20 amp may protect the traces but may have allowed damage to the FET's. When I get it repaired I'll probably put max 10 amp fuses in the TIU. With 4 amp circuit breakers it shouldn't blow a 10amp fuse unless something bad is happening and maybe a 10 amp fuse would have saved it in the first place. I realize on a larger layout with multiple engines on a single TIU you need a fuse larger than your circuit breakers. But if you are running 10 amp breakers, or quick blow fuses I (MPO) would use no larger than 15 amp in the TIU.  I realize in my case there is no way of knowing which came first the chicken or the egg, but smaller fuses in the TIU may have prevented damage if the short was external of the TIU.

I don't know how "fast acting" the breakers are on those, I had a guy with a couple of Z1000 bricks, and the 20A fuses in the TIU were blowing all the time, the breakers on the bricks never tripped.  Those are thermal breakers, and they take quite a jolt to trip quickly.

You raise some good points. Apparently each tiu channel is rated at 10 or 12amps so why would the  internal fuse be rated at 20 amps? Perhaps the tiu can handle a little more than advertised.

 We have 4 tiu powered by post war ZWs and haven't lost one yet because  of the 10 amp  external 32 volt fast blow fused between the power supply and tiu input, One fuse for each channel.  This way we don't have to take the tiu apart to change a fuse.  It's too bad you got off to a rough start with a faulty channel and it also  sounds to me like the remote may have issues as well (loose transceiver board) hang in there.

Well I'm better now. It's the price for being cheap. Now in the long run I do good. But with bargains, sooner or later, you have to pay for all the other good deals. It's my time to pay up.......... I guess since I have issues I will go ahead and reseat the board in the remote. And I don't like to upgrade anything that's working, but I have 3.0 software, and I have the cables so I guess I'll go for broke and upgrade the software before I get the TIU repaired. I can use it as is. I just cant operate a conventional locomotive on the upper level, (with the remote). I have toggles switches so I can change either track from my conventional transformer to DCS. It's all good now, last nite this time, I was almost to the point of wanting to bust something....................... If this was a job, well ok, but it's a hobby, supposed to be relaxing, fun. And last nite DCS had sucked all the fun out of it........

Charlie,  Do you know if the TIU Variable channels were ever set up/used as "Fixed" channels?

Charlie Howard:

It was my TIU that gunrunnerjohn was referring to. The brick driving the fixed channel was the 100watt MTH power brick. Every time the train derailed (I had some early track problems now fixed) the 20 amp fuse in the fixed channel would blow and the bricks 7 amp breaker never even quivered. This happened a half dozen times, each time requiring pulling the TIU off its mount point and breaking into it to replace the 20 amp fuse. At first I used the passive mode so the current would not go through the TIU but I eventually added a separate very fast acting circuit breaker (magnetic, not heat activated). Now any derailment instantly trips the separate breaker and I have not lost one 20 Amp fuse since.

Other than this problem the TIU and the associated AIU have worked fine. I found out you have to follow the startup procedures or the engines will get in never-never land and not sound or not run. Follow the procedure and it all works fine. I did have one engine that lost sound above 40SMPH but a Feature Reset fixed that. You have to follow the procedures or things get screwed up. That's not the DCS but an operator error.

I'm sure you realize this but just for drill, did you power up channel one when using the variable channel? The first fixed channel powers up the computer part of the TIU whether you connect channel one output to the tracks or not. An option to that is the aux power in port. I'm pretty sure that is not your problem since you said you blew a fuse immediately which probably was an indication that that variable channel had a problem.

LDBennett

I believe the early TIU did not have fuses at all.  In reality your expecting the transformer to do the protecting.  I guess it is a balancing act between continuity of power and protection.  I think the casual hobbyist isn't thinking to open the product to replace a fuse.

Too much of the hobby was depending on PW transformer early on.  Now there are fast acting breakers on power supplies.  I got to give credit to Lionel with the Power Houses, which I use on my layout.  They kill power before you even realize you have a fault.

So I think the internal fuse is to protect the integrity of the TIU, and the expectation is external breakers and power supplies are protecting the equipment.  

For the skilled hobbyist adding quick blow fuse at the 8 to 10Amp rating would be added protection.  G

No I don't. I tried setting VAR2 as Fixed, but it still only passed 3.8 volts. I did a factory defaults reset, with the same result.

Yes I have power, (from 1 Z750 brick) powering VAR1 and FIXED1. I think the fuse was blown prior to hooking up VAR2. I purchased this used. After reading all this I think I'll put some inline fuses in as well. The breakers on my bricks seam to trip almost instantly when a derailment occurs, and since they were 4 amp breakers I felt safe. But now I believe I'll add the fuses just to be safe. But I still also believe (right or not) that the fuses in the TIU are too large. And will replace them with smaller fuses. I have 4 amp breakers in the bricks, so I'll probably go with 5 amp fast acting fuses (in line) and 7.5 amp in the TIU, or 7.5 amp (in line) and 10 amp in the TIU. Since I have a small layout there just is not the room, (track) for more than 2 engines on the same track. Where had I a large layout, (more trains on 1 channel of the TIU), I can see where I would need closer to those 10 amp fuses. And since now you have me paranoid that these breakers take more amperage to trip than they are rated at, I'd rather replace a few fuses as opposed to having the TIU repaired again.

I personally wouldn't fool with the TIU fuses.  However, if you must, I certainly wouldn't go less than 10 amps.