# Train Engineer Develops an Interesting Problem. Any Thoughts?



## toddalin (Jan 4, 2008)

It was hot (~90s) at our open house yesterday and one of the Train Engineers developed an interesting problem. I don't know that this was caused by the heat of the day, from last weekend's outing in the rain, some combination of both, or just age but:

I had an Aristo FA/FB/streamliner consist, a USA GP-9/freight consist, and the aerial tram all running on one 10 amp TE powered by a Meanwell 24 volt, 12.5 amp supply (at 22 volts input). No big deal and this is the usual fare

Worked fine last Sat and for a bit when I started out yesterday. Then the trains stopped. The circuit breaker (fuse replacement) was fine and the Meanwell put out power, but when raising the throttle voltage on the TE, it would go up to between 4.5 - 6 volts then drop to zero each time I would try to bring up the throttle.

The breakers didn't pop and I had the same results turning off the aerial tram and removing the trains from the tracks.

OK, perhaps a "partial short" across the rails?

No.

When I switched those routes to another cab (also a TE), they worked fine and after it cooled down a bit I just ran the four trains (two on the other TE), and aerial tram on one TE and they performed flawlessly. I didn't want to do this during the heat of the day for fear of loosing another TE and having even fewer trains run.

So, any thoughts or similar TE experiences as to the problem and how to go about fixing it?


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## Dan Pierce (Jan 2, 2008)

I assume by Train Engineer you are using the black jandheld which is 27 mhz.
Also I assume the black plastic case receiver.

And for operations in the heat does this unit have a fan? Lewis changed the spec form 5 amps for the fan to 3 amps but never updated the manuals. All pf my TE's have fans.
Are you in linear or PWC mode?


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## toddalin (Jan 4, 2008)

10 amp, 10 channel, 27 mHz trackside unit with black hand unit.

Receiver has the fan and the fan was running as normal when it does its reset to zero thing.

I alway run in linear mode because of the sound units on the engines and other sensitive 555 circuits in the system.

Rooster thinks that maybe the fan is causing this problem and I'll have to try it again with the fan disconnected when the weather cools a bit.


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## Dan Pierce (Jan 2, 2008)

Hard to believe the fan is the issue as there is a 12 volt regulator feeding the fan.
But disconnecting the fan would not hurt anything for testing the unit.


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## toddalin (Jan 4, 2008)

Dan Pierce said:


> Hard to believe the fan is the issue as there is a 12 volt regulator feeding the fan.
> But disconnecting the fan would not hurt anything for testing the unit.



Agreed.


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## toddalin (Jan 4, 2008)

The transmitter links and the unit changes direction but puts out max voltage on the meter. This is typically due to an internally shorted FET.


But, I'm thinking it's a 1 uH SMD piece in the circuit. I should get continuity across it and I don't. And it looks white and fuzzy and melty.


When I try a different TE (but not identical) that also has this portion of the circuit, I get continuity across this same piece. The other TE also gives all the same values fore the legs of the semiconductors, so none would appear to be shorted out internally.


Also, luckily, the other TE lists the parts on the board whereas the broken one doesn't. That's the only way I can tell what burned out the part is.


Where does one find elves with fingers small enough to resolder/resolder SMDs?


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## Dick Friedman (Aug 19, 2008)

For the electronically illiterate (that would be me) please translate 1 uH SMD? Todd, can you reply (off line if necessary) with the faulty components in your photo circled? My old eyes can't see any difference. TIA.


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## Cataptrra (Mar 16, 2015)

Dick Friedman said:


> For the electronically illiterate (that would be me) please translate 1 uH SMD? Todd, can you reply (off line if necessary) with the faulty components in your photo circled? My old eyes can't see any difference. TIA.


1uH SMD = a 1 micoHenry "S"urface "M"ount "D"evice. These are extremely and I do mean extremely small components, it requires a very fine tipped VERY LOW WATTAGE soldering iron ior you'll damage the PCB in trying to replace them.

You actually need a voltage controlled soldering station to work on these types of components, they can be damaged and destroyed very easily if the wrong type soldering iron and tip is used.

You can't use the standard over the counter hand held soldering iron you can buy off the shelf at an auto parts store or local radio shack, they are too big for the task!


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## Cataptrra (Mar 16, 2015)

toddalin said:


> The transmitter links and the unit changes direction but puts out max voltage on the meter. This is typically due to an internally shorted FET.
> 
> 
> But, I'm thinking it's a 1 uH SMD piece in the circuit. I should get continuity across it and I don't. And it looks white and fuzzy and melty.
> ...


It's not easy to replace SMD parts, I used to do that for a living, but can't do it any longer due to now being legally blind.

But here's a possible solution to your problem, my Receivers are left out in the weather all the time, I've had similar issues and see the white fuzzy stuff all the time on my PCB in the Receiver because it gets damp and sometimes a bit wet from the rains. Some SMD parts may appear to look melty, but may not be melted at all, it's just the way they look at times.

Now the white fuzzy stuff, that's usually a type of mold growing on the PCB from where it's been outside in the elements, very carefully get a few cotton swabs and some denatured alcohol and clean the white fuzzy stuff off the part, the PCB and around the components legs/leads.

Allow to dry or use a blow dryer on the lowest setting, although the denatured alcohol tends to dry up quickly on its own, and blow the PCB dry{don't get the PCB too hot, those SMD parts don't require much heat to become unsoldered and blow away off the board, so don't get the blow dryer too close!}

Before fully reassembling the Receiver back in it's case, connect it up, power it and test. Hopefully this will resolve the problem as that white fuzzy mold seems to be able to conduct and create shorts, just not enough of one to usually blow the 10amp fuse, just enough that it allows the train{s} on the rails to get into "run away" mode.

At least I've done this with my Receiver and afterwards, it started working just fine again.

So hopefully this is the same issue you're having and this cleaning the PCB of any/all of the white fuzzy stuff will clear up the issues.


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## toddalin (Jan 4, 2008)

Know this about the Train Engineer. _*The fuse is NOT on the output but on the input!*_ So something "down the line" can mess up its guts without even popping the fuse.

The 1uH is bad as it is "open" (no continuity) when I compare it to another TE. Also, it mostly disintegrated when touched. (My stuff is not left outside, but kept in the garage.)

Also, the adjoining transistor is probably bad as it doesn't read the same as another TE. (One piece will usually take the other out.)

Actually, now soldering irons are not used to mount/remount SMDs. (Too small and crammed together.) 

These are now done with "hot air" soldering stations. You just blow hot air at the piece and remove/place it with a tweezers. And I do have access to two of these through the Urban Workshop.


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## Dick Friedman (Aug 19, 2008)

Todd, did you not get continuity before or after you removed the 1uH SMD (I got the jargon already, I just don't know what it's supposed to do) from the board?

And where is the potentially bad transistor? Thanks for your patience. I'm so backward I still listen to cassettes in my car!


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## Cataptrra (Mar 16, 2015)

toddalin said:


> Know this about the Train Engineer. _*The fuse is NOT on the output but on the input!*_ So something "down the line" can mess up its guts without even popping the fuse.
> 
> The 1uH is bad as it is "open" (no continuity) when I compare it to another TE. Also, it mostly disintegrated when touched. (My stuff is not left outside, but kept in the garage.)
> 
> ...


Interesting, I always thought the fuse was on the output of the receiver, if I get a short in a loco on the rails it usually always blows the fuse. And then I have to track down the issue in the loco.

interesting about the new way to solder SMD components with that device, that would have been a LOT easier if we'd had those instead of the fine tipped soldering stations we had to use back in my day!

I thought your receivers were outside from what I had read in your initial post, must have gotten mixed signals on that one, so my error.

Just know I've had similar issues, but it was caused by the white fuzzy mold or corrosion on the PCB, cleaned it up and I was good to go again.

So thought it might have been close to the same issue with your problem, but see you've found the culprit{s} and it wasn't the same problem that gave me issues.


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## toddalin (Jan 4, 2008)

Dick Friedman said:


> Todd, did you not get continuity before or after you removed the 1uH SMD (I got the jargon already, I just don't know what it's supposed to do) from the board?
> 
> And where is the potentially bad transistor? Thanks for your patience. I'm so backward I still listen to cassettes in my car!


I've not removed it. A 1 uH SMD is essentially a coil and a coil should show continuity across its leads. The bad transistor is the one that attaches to the 1 uH SMD. It's also an SMD.


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