reversing loop module failure

[Anonymous]

I had what you Americans call an open day here last Saturday and lo and behold one of my reversing loop modules failed. Has anyone else had a failure?

I was running my ICE train under slightly damp conditions and halfway around the loop it stopped and i thought it was power pick ups on the ICE train.

However i put my Mallet on and it wouldn't go either!

I removed it a few days later (the module that is) pulled it apart and under the circuit board i saw a nasty brown spot, i think it has blown a capacitor.

Any views gentlemen and ladies.

Rgds ian

[amotz]

Ian:

A diode can do that if overloaded (sometimes surprisingly quickly).

Arthur

[Anonymous]

Yes but it was only being operated under pretty normal conditions (for Europe that is) why would it overload?. i am also pretty sure that the component on the other side of the board was a capacitor, why would it fail?.

In any case the local distrinutor has sent it off to Germany for examination and has sent me a replacement at N/C by post already; which i think is outstanding service and attitude.


Rgds Ian

[Tom The Brat]

They'll take good care of it.

Years ago, I had a computer terminal (CP/M computer) that would blow up a 35uFd capacitor every few months. RS sold them 2 for 89 cents.

[markperr]

Back in the days when I used to fix computer monitors, we used to switch out capacitors on a regular basis due to heat conditions. The OEM caps were rated at 85 degrees celsius and would fail regularly, so we switched them to 105 degree celsius caps and the problem was solved for good. With caps, it's hard to say why they fail. Sometimes the magic smoke switch just stops working properly and lets it all out. More times than not with a rather loud KAPOW!

Mark

[Tom The Brat]

Called the terminal, "Fluffy" for all the brown fluff inside it[:p]

[Anonymous]

Ok thanks you blokes, i will now go on with my life feeling safe and secure.

Rgds ian

[Tom The Brat]

Prolly won't happen again.

[Anonymous]

I agree it is a one off thing i hope. Only worry is is had the idea that it didn't fail for nothing and having wet ballast between the rails may have caused an impedance imbalance and it may happen again under similar circumstances. However i have another one at the other end of my layout and its older and nothimg happened to it.
Also it doesn't rain much here, like hawaii it buckets down of a night time mainly so it may never happen again.

heres hoping.
Ian

[Tom The Brat]

Na... Wet ballast didn't do anything to it.

[Anonymous]

I tend to agree with you but have seen funnier things than this cause electronic problems.

Ian

[grandpopswalt]

Ian,

Is there any chance of unusual electrical noise in that area of the track getting into the module? Remember that the cap will try to charge to the peak of the noise and if it's above the cap's voltage rating, pow!

Walt

[cacole]

Wet ballast between the rails could have caused excessive current draw and overloaded the reversing module. Was the module itself wet? Water between circuit board traces can short them out.

[Anonymous]

Well gentlemen thank you, some worthwhile comments i'm sure.

The unit it self wasn't wet inside or out and upon close inspection no ingress of anything was detected. My gut feel was that what cacole said is pretty right but i have no real reason to believe this either.

Walt your idea of electromagnetic noise is worth considering.

I have 2 of these units and the other one is much older than the one that went down but the faulty one is located much closer to a road that is fairly busy and right on a roundabout, anything could have come past and induced stuff into it.

In my opinion at this stage; and in light of what LGb had to say (replacing immmedialtey at no charge and sending back to germany for examination) leads me to believe it is possibly just a companent failure; and they do fail from time to time for no real reason i guess.

Rgds Ian

[Anonymous]

New information.

I recieved my free replacement in the mail yesterday (aust EST) and immediately went out to replace same. Getiing out my trusty multimetre to make sure all the polarities were correct i came upone something very rare and it still has me stymied .

The reversing loop and a switch decoder are connected to a 1052T isolating unit. to provide connection to the main rails to pick up connection from MTS and i found a 186 ohm resistance within its terminal block, on the blue or outer leg. I checked it about a dozen times and got much the same every time say 194 ohn maximum. I shorrted the problem out and connected everything up and it works perfectly!

I don't know for sure; as i couldn't get under the printed circuit board type connection to inspect it properly but i suspect ants, as they are pretty prevalent in this area.

Questions.

1/ Does any one else think it it could have been ants and if so how could they cause this problem?
2/ Does anyone think it may have caused the capacitor to blow in the reversing loop module? I had the idea of a constant wattage device as the voltage across it dropped the current would increase, any chance?
3/ How could anything run in the reversing loop with this terrific resistance in it?
4/ does anyone thing the wet weather may have excaserbated the problem?
5/ This is a very odd resistance to happen by chance, too high for a partial short and too low for a high resistance joint?
6/ How did the switch decoder work under these circumstances and it must have as it was on the same circuit.


Lets hear what you think gentlemen.


Rgds ian

[Tom The Brat]

You mean 186 ohms between + and -?

Ants can leave a conductive trail, but it's usually a pretty high impedence.

[grandpopswalt]

We once had a problem at an outdoor well pumping station where a mouse got between a circuit board and a 600 volt DC buss wire. Happens that the mouses' butt was on a ground pad and his nose was on the buss. He quickly turned into carbon and became very conductive indeed, enough to blow up a 200 HP AC inverter. So strange things do happen when these crtters get into places they don't belong.

Walt

ps
I'm with Torby, I think you had a defective unit.

[Tom The Brat]

Remember a couple years ago a flaming squirrel falling from a power line set a huge fire... Explain that to the insurance adjuster!

Are these units protected from moisture and from bugs crawling inside them?

For you 186 ohms, I would expect many kiloohms. Try cleaning that junction dealy out or look for smashed weeds, caterpillars, snakes, dugongs and whatnot laying across the track.

[Anonymous]

Yes Walt i think your right it was a faulty unit, pretty rare but it does happen.Being the person i am i try to find out truly if i have done something wrong then try to make sure it wont happen again. In other words if this was caused by a local phenonema, i wont to make sure it doesn't happen again.

Torby it was between 186 and 194 ohms.

Still it was very interesting.

Rgds ian