MRC 2500 DC TRANSFORMER PROBLEM

[davidone]

Unpacked my trains today and was going to do some testing but when I hooked up my MRC 2500 Transformer. I hooked to variable dc but when turning it on the train started moving at a slow speed without touching the throttle.
Why is this doing it? The throttle was set at zero so the engine should not move. I was running two Atlas gp38 that are pretty recent I believe.

Any help?

Dave

 

[bnsf971]

Sounds like a bad potentiometer. Are you sure the throttle is set to 0? What happens when you change directions on the control?

 

[davidone]

Same thing happens, if it is the potentiometer can it be fixed and replaced?

 

[bnsf971]

Same thing happens, if it is the potentiometer can it be fixed and replaced?

It depends on how good you are at repairing electronics, and whether you can find a replacement you won't have to perform major surgery on to get it to fit.
Does this have momentum on it? If it does, try turning that off, see if it changes anything, turn it on, and check that, as well.

 

[davidone]

Yes I turned off the momentum, no difference either.

 

[bnsf971]

Yes I turned off the momentum, no difference either.

A quick Google search shows this is a common problem. Since this seems to be such a common problem, it would probably be a good idea to just find something better, unless you're emotionally attached to this one for some reason.

 

[davidone]

I took it apart and the pot is the least of the issues. I'll keep it as a parts donor if ever needed. I just bought 2 new transformers so now I'm all set to run some trains. I knew the 2500 had some issues when new and the pot was one of them. Bad design from the start and almost impossible to work on on unless you were a engineer!! MRC dropped the ball on this one!!

 

[bnsf971]

MRC dropped the ball on this one!!

It's 45 years old, so I don't know how many balls were dropped. I wonder how much current technology will still be working in 45 years.

 

[santafewillie]

I wonder how much current technology will still be working in 45 years.

It's not so much whether it's still working, but whether it is made obsolete by then...

 

[davidone]

Just because its old does not mean it should not work. I was hoping to fix it. I don't believe in a throw away society. But yes in this case its not worth fixing anymore beings I have almost rebuilt it over the past twenty years.

 

[PaulieT]

One thing that routinely fails in old electronics are the capacitors. Electrolytic capacitors are the worst, as most are only rated for around 2,000 hours. However, depending on the circuit design, you can get 10,000 hours or more on these capacitors. It comes down to things like ripple current, operating temperature and operating voltage vs rated voltage and size.

I have some old test equipment that works perfectly after 20 years and had some audio equipment, that failed after only 7 years. The better the design (more conservative and robust), the more expensive it becomes. To make power packs affordable, I'm sure the design is not overly conservative.