I have an old HO set that I haven't run in many years. Trying to get it set back up. Starting with just a basic setup. One oval with a Tech 4 MRC 220 transformer. I've run wire from the variable DC screws on the Tech 4 to the track. The train does not run. I took the engine to a local hobby shop and it ran fine on his track. Using a multimeter, with the train off the track, I am getting good power readings to the track, however, as soon as I put the train on the track, readings drop to zero. Is this normal? Any ideas what I might be missing? Thanks in advance for any suggestions.
Sounds like this is tracing back to the power pack. Does the loco run if you apply the pos/neg wires directly to the pick up wheels? Is there any arcing and sparking if you brush the opposed wires against one another?
Place your multimeter leads on the power pack's variable DC output and turn the throttle knob back and forth. Does the meter respond as you'd expect, reliably rising and falling with voltage changes? If it does, I suspect your locomotive has an intermittent problem. Remove the shell and try to run the locomotive and look for signs of arcing or sparking as @Chops suggested. My guess is that the motor brushes or power pickup are dirty or that there's a short in there. Aside from those, the only other thing I can think of is if your track is very old, it's made of brass, is oxidized and won't conduct well to the locomotive wheels.
The loss of voltage under load indicates a high-resistance connection somewhere between locomotive and the power supply, or within the power supply itself. By itself, the multimeter provides very little load (and therefore no current path to build up voltage loss across a high resistance.) Thus the difference between your readings with/out the locomotive present to provide a current path. This high resistance can be caused by corrosion and/or dirt, likely where wires are joined to power pack or track, or on the track itself. By measuring the voltage at various points along the path from locomotive back to the power pack, you may be able to determine where the dirt/corrosion is located. I would focus on any connectors or screw terminals, as well as the surface of the track. Spray-on "contact cleaner" can help when you find the problem, but it can destroy some plastics and paint finishes, so use with due caution. It is also possible the problem lies inside the power pack, so opening it up and inspecting it for obvious signs of corrosion would be prudent if prior efforts fail to reveal the problem. Proceed with caution if you try to measure voltages inside a powered pack. Dragons be there! Hope this helps, and keep us abreast of your progress.
MRR DC Train controllers are essentially dc power supplies. If the loco tests good elsewhere and the power pack voltage is measured by a meter, the following points.. As BigJake says, the power supply needs to be tested under some load, maybe you have an incandescent 12V bulb around? If the contacts are clean and visual inspection reveals nothing, then... The power supply should easily provide the set or stated voltage at up to the maximum current(or power) output specification before the output voltage is adversely declines, if a power supply gets "loaded down" below its designed rating, points to a number of things including leaky capacitors in filter section, a bad rectifier diode (in FW or bridge) or in the voltage regulator. Prior to filtering, the rectifier(s) convert AC to Pulsating DC. It is the filters job to smooth out to effective DC and a decrease in filter capacitance under a given load would result in higher ripple (undesirable) and lower DC output voltage. (Digital Meters have fairly high input resistance Meg ohms and do not place the supply under load.. Less likely for supply issue shorted xformer windings. Cold solder joints-improper cooling. Can be fine at first and over time become either faulty or intermittent. if you are good at soldering and can inspect for cold solder joints, I've gotten stuff to work just by re-heating.
Still in the stone age. The answer was there all along. A quick check with the voltmeter will rule in or out the transformer.
I wanted to thank everyone for the feedback here. I've been playing with this on and off for the past few weeks and finally realized the issue yesterday. My multimeter was giving me consistent reading around the track, but yesterday, I finally realized the reading was in mV, not V. So, bad power supply is the source of the issue.
