Track Power
Voltage vs Scale Recomendations
At no load, a typical open-frame unregulated power supply will put out more volts than it is rated for. For example, a 14-volt power supply will put out 15 to 16 volts. But, when it's loaded with the rated current, it will sag to its rated voltage.
Team Digital note: See Power Supplies for additional information.
Boosters have voltage regulation built in. That is, they try to maintain a certain amount of voltage on the track at all times. When power-supply voltage fluctuates due to sag or house-voltage variations, track voltage will remain about the same.
For regulation to work, there must be more input voltage than the regulator is set for. That is, if you're trying to regulate at 15 volts, you must have more than 15 volts going into the regulator for it to maintain 15 volts. How much more? Just more. But if the house voltage fluctuates, more today may be less tomorrow. So you need enough more to accommodate power-supply variations, and house-voltage fluctuations - say, two volts more.
When you put AC voltage into a booster, the first thing it goes through is a bridge rectifier to convert it to DC voltage. When it goes through this rectifier, it gains about 40% in voltage, then looses a few volts when going through various electronic components of the booster.
Let's say we're using a 14 VAC power supply for HO scale. This converts to about 16.6 volts when factoring in electronic component drop - only about 1.6 volts more than is needed for the track. But remember, an unloaded power supply puts out more than its rating. So if we figure that the power supply will really be putting out about 15 VAC most of the time, we'll have about 18 volts to regulate down to 15 volts - enough for good regulation.
While this excess voltage has to be burned of as heat, it is necessary for good regulation. More voltage than that will gain you nothing, and will have to be burned off as even more heat.
So the key is this: put in the voltage that is ideal for the device. Any less voltage makes performance suffer. Any more makes excess heat that has to be dissipated.
The ideal input voltage depends on which scale setting your booster is set for, not what scale you're actually running. The booster puts more voltage on the track when set for HO scale than when set for N scale, so it needs more voltage in when set for HO scale than when set for N scale.
• For the N-scale setting, 12 VAC is about ideal
• For the HO-scale setting, 14 VAC is about ideal.
• For the O/G-scale setting, 18 VAC is about ideal.
The ideal voltage is different if using a DC power supply. When going through the bridge rectifier in the booster, DC voltage does not increase like AC voltage does. However, it still loses voltage as it passes though various electronic components. So, if using a DC power supply:
• For the N-scale setting, 16 VDC is about ideal
• For the HO-scale setting, 19 VDC is about ideal.
• For the O/G-scale setting, 25 VDC is about ideal
Heat
With all things electronic, heat is the enemy. Now, I can't say that if a booster runs cooler it's guaranteed to last a certain length of time, no more than anyone can say if you don't smoke you'll live to be 100. All boosters are different, used differently, and will have different life spans. But, like not smoking, we can say that if a booster runs cooler, its life expectancy will probably be longer than if it runs hotter.
Right here, I want to make something very clear. If your booster, without a fan, is heating up to a point of shutting down without continuously drawing at least 75% of its rated power, something is wrong. Either the booster is defective, or the power supply is putting in too much voltage. And while you should use a fan on your booster whether or not it is over heating, putting a fan on an overheating booster will only mask the real problem - the problem of making too much heat is still there. If your power supply is putting in too much voltage, causing this problem, get rid of that power supply, and get one that puts out the correct voltage for the scale setting you are using.
There are two components to heat: making heat, and retaining heat.
Putting a fan on the heat sink will dissipate heat that is made, and prevent heat buildup. But it won't stop the components from making excessive heat to start with - and making excessive heat can be almost as bad as heat buildup.
The best tactic for the longest-possible booster life and best performance is two steps: first use the correct voltage for the scale you're running (to lessen the amount of heat made), then put a fan on the heat sink to dissipate what heat is made.