Household outlet

gerty

Joined Aug 30, 2007
1,267
Input: 120V, -50/60HZ, Output: 17 VDC, 20 VAC, max output: 7 VA total; Second one where the engine just suddenly died without notice: Input: 120 V, AC60Hz, output: 19V AC 0-18VDC 5.5 VA. The train runs on the DC power. The engine is a new Athearn which was given to me this summer for my
What I was referring to was the va capacities you listed, not voltage but current (va).
 

gerty

Joined Aug 30, 2007
1,267
Also, another thought: If the curcuit was over loaded, wouldn't the curcuit breaker in the breaker box "pop" and shut down?
If the transformer was overloaded it would burn out, like they have been.
If the 120volt circuit was overloaded the breaker would trip, which it apparently it hasn't.
Overloading the small transformers secondary shouldn't make it draw enough current on the primary (120v) to trip the breaker.
 

gerty

Joined Aug 30, 2007
1,267
You still haven't told us what the old transformer is rated at for current or va.
The voltage you keep mentioning isn't the issue. It's all about the current in this case.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
The information on the old transformer that works is as follows:
Input: 118V 60 CV;
Output: Open circuit, DC 16.5 V, AC 17.5, Max output 10V.A-1AMP.

I am trying to attach photos of the information on the transformers.
#1 is of the old transformer that functions,
#2 is of the transformer that shut down without notice, &
#3 and #4 is of the transformer that gave out slowly. This transformer is not photogenic.

Can you run the current stuff by me again please? I am not sure which numbers you are speaking of.
 

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SgtWookie

Joined Jul 17, 2007
22,210
It's the VA rating against the output voltage.
Your old transformer can output 1000mA @ 10v.
The "model power" can only output ~300mA total
The last one can only output ~400mA total
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
OK, so which number on the transformers do I look for to determine these output numbers of 1000 mA, 400 mA & 300 mA? And since the old one still works I guess I need to look for one that does 1000 mA or more...
 

SgtWookie

Joined Jul 17, 2007
22,210
For your purposes, just think of VA as Watts.

VA or Watts / voltage = current
So, if you have 7vA at 17v, that's 411.7mA.
That's the maximum rating for both outputs of that power unit at one time. So, if you have 200 mA coming out of one side, the other side only has 211.7mA left.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
If I understand you correctly, based on the old transformer (#1),
10VA/ 16.5 VDC actually equals 606 mA, not 1000, or am I using the wrong numbers? For the other two transformers I got similar numbers to the ones you are showing me.

Transformer #2: 5.5 / 18 VDC = 305 mA;

Transformer #3: 7 / 17 VDC = 411 mA;

Did I miss something or make another mistake? I am thinking I may not be using the right numbers...
 
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SgtWookie

Joined Jul 17, 2007
22,210
If you look at the 1st transformer again, it says 10VA - 1A. So, if it's outputting 1A, the output voltage has dropped to 10v.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
OK on the 1st transformer, but I don't understand how it went from 16.5 to 10. But that's okay.

The new to me transformer I am waiting to arrive which I bought on eBay as the following specs: Input: 120 VAC 60 Hz, Output: 14 VDC, 18 VAC, 13 VA.

So : 13 / 14 = 928

Do you think this will work out ok?
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
The new one I am buying is a MRC 1400, if you need to look the specs up on the internet for further information.
 

SgtWookie

Joined Jul 17, 2007
22,210
That will probably do the trick.

As far as your old transformer and the rivets; they are not hard to remove if you have an electric drill and a selection of drill bits. You just need to be careful to not let the drill bit go through and damage the transformer inside the box. It's easier if you have a drill press available.

To put the thing back together you could either use some kind of sheet metal screws, or perhaps get a Pop Rivet tool.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
Going back to taking the transformers apart, I really don't want to open or damage the one that works. The two others that broke down have all plastic shells and they don't have rivets or anything. They appear to have been glued together or fused some how. I tried prying them apart with no luck. I have another old one that no longer functions. I may be able to open it later. It's DC output no longer functions, but the AC functions just like transformer # 3.
 

SgtWookie

Joined Jul 17, 2007
22,210
Well, the one which has no DC likely has a bad rectifier bridge and/or filter capacitor. When filter capacitors go bad, they can short out, which will take out the bridge at the same time due to excessive current.

Since your original transformer is noisy, you don't use it anyway except in "emergencies" like this. Might as well take the cover off after the new one arrives.
 

Adjuster

Joined Dec 26, 2010
2,148
I think a careful examination of the track and engines might be called for. Intermittent short-circuits here might be possibly be harming your transformers.

I would expect that a well-designed model railway transformer might have some protection against such mishaps, such as a thermal cut-out, but nothing is perfect.
 

SgtWookie

Joined Jul 17, 2007
22,210
Thinking more about what Adjuster said - have you ever used steel wool to clean your tracks? If so, you better run a magnet all over your layout, because steel wool will cause shorts all over the place - and steel wool will also start FIRES if current is put through it!

So, keep steel wool far away from your layout.

I'm thinking you may wish to use something like an automotive bulb in series with your track supply. If a short develops, instead of shorting out your supply, the bulb will get bright. Normally, the filament should be practically cold, and barely producing any light.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
I dug out the mentioned transformer and managed to get the cover off of it. The wire that "was" soldered to the speed control lever had become disconnected somehow. I soldered it back on. Now I have it connected to the layout and it is working just fine. It is rated very low with a 333 mA, if I got the numbers correct. I guess I will see just how long it will run and go from there.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
Tell me more about your automotice light idea. It sounds good, because I like things to be visual whenever possible.
 

Thread Starter

maassmi

Joined Oct 30, 2011
81
Adjuster: This layout is a simple oval with nickel-silver track. I am including a couple of photos. As you see, the wires go directly from the transformer to the track. The track is clean, but I can run track cleaning car over it and see if anything changes. The locomotive is a new locomotive and I just lubed it just in case it needed it. There should not be any issues, except for the transformers ability to do its job. I am noticing that the train is slowing down though. So, I just got up and adjusted the "throttle" to speed it up and then slowed it down a little again, but not to the point I had it earlier. Keeping it a little faster.
 

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Thread Starter

maassmi

Joined Oct 30, 2011
81
If anyone is interested, I have some short videos of my layouts on YouTube. This one for Christmas and my big one out in the garage. My name on YouTube is RockyLinesHO. Should be easy to find...
 
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