I recently acquired an OLD 4X8 HO layout for CHEAP that included 3 MRC Railine 370 power supplies. I have tested them and they all put out 20V AC and 15V DC but none appear to have a functioning speed controller. The output voltage is either 0 or 15 with no variation over the range of the controller. I have simply hooked the output up to my multimeter to check the voltages. I opened one up to see what was happening and there is a wiper that runs across a wire wound resistor feeding one of the output terminals. No surprises there, but regardless of where on the resistor the wiper is, the output is still 15V. Am I missing something?
Put a load on it, such as a tail lamp bulb and repeat your tests.
Jim
These are variable resistors and not voltage regulators. They must have a suitable load to work. The load must also be suitable. This is why some of these old power packs had different models for HO and N scales. The motors placed differing loads on the power pack.
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Newer locomotives with low draw can motors sometime do not work well with these old power packs because they do not have enough load for the variable resistors and the starting voltage will be too high.
Yes, check them with a load. Or... why not test them with a locomotive on the track?
-Kevin
Living the dream.
Well, Duh! Got the railroad running and two of the three throttles work just fine. They are definately different from each other. Using a recently acquired locomotive one throttle is very sensitive and delivers 10V within the first quarter of the knob's travel. The other needs almost full throttle to get 10V. Not unhappy at all as both work fine. The third was damaged and the throttle was no longer operable. I replaced the wiper with a permanent hookup to the DC output. I wil use this for power for accessories. 17VAC to switch machines and 15VDC for panel lights and signals. These power packs are nothing to look at but work great. Worth the $20 even without the layout!