Model Rectifier is a good old brand and even a 40 year old MRC “power pack” should still give good service provided it has not gotten wet or been mistreated. I suspect as your trains ran that the wheels of the train redeposited dirt onto the rails. Take a paper towel soaked in rubbing alcohol and put it over a piece of track. Run each car over the moistened towel with your fingers and it will pick up dirt. Move the towel around so the wheels are touching fresh paper.
You can even run the locomotive over this paper towel and it will remove some dirt. I bet that will help.
Also eventually you may want to run wires to the the farthest part of the track, so that the power pack is connected to your oval or track in more than one place. Make sure you keep + and - separated and don’t short out and you should be fine. That increases the reliability.
Dave Nelson
Roosty, your problem with slowing down may be due to something else besides dirty track. If you have cleaned all the things that the previous posters have suggested (all good suggestions, by the way) and the loco is still slowing down, you may have motor magnets that have lost most of their magnetism. Motors that old would have Alnico magnets, which lose their magnetic strength over time.
If this is the case, you have three choices: 1) remagnetize the motor - a procedure which requires a specially built electromagnet that is quite powerful, and usually beyond the resources of a beginner, or 2) replace the motor magnets with new ones - preferably the new supermagnets - available on the net - but that might not be possible or worth doing, depending on the model, or 3) replace the motor.
If all of the above fail, replacing the locomotive is about your only option.
The primary signs of a weak or failing magnet is slower operation, increased current draw, and overheating. If the overheating is occurring, and the mechanism seems free, then weak magnets are almost certainly at fault.
Good luck, and let us know how things are going. Post some pics! [:)]
Texas SP,
If you don’t mind my asking, How did you get those custom signs?
It’s top secret information I can’t really share, in fact the black trucks are pulling up in front of my house as I type…
Seriously, I have amassed many forum response type pics from different forums and places on the net over the years. I pop the ones I really like on my photobucket account for later use. When I see what I want I just right click and save the picture and that is it. Feel free to use this one at your leisure.
Here is another of my favorites for when a topic starts to create a rather heated discussion:

Quick! Before they pull out a battering ram, set the computer on fire! then they will have no evidence agenst you.[(-D]
But, another question before you start the fireworks,
Insted of a photobucket acount, would a blank E-mail draft work?
Never tried it so can’t answer. Photobucket just makes it quick and easy since the give you the direct link code. Just copy/paste and the picture shows up when you post.
Another thing you should note is the reason for the post. Do you want to sell the set? Or do you want to run it? The initial post suggested that you finally got ahold of a bag of cash