The MOST IMPORTANT TEST. is to determine if there is a working circuit breaker. Every pack should have one, even if it is external.
Back in the middle 40's, my younger cousin decided to sneak in and run my trains with an old Lionel K 150 W transformer. When the train derailed, he disappeared. Luckily I arrived a little later and found the formerly cloth covered connecting wires glowing incandescently. The adjacent plywood was only slightly charred. BUT!!!!!
Testing for a working breaker is very simple and nothing should be damaged unless the breaker is faulty or absent. Just short the terminals with a screw driver for a few seconds and the output voltage should be removed. After removal, it should return in so many more seconds. Some packs have a red indicator light that glows when the breaker is activated and some can be heard. If not, a small bulb can be connected between the terminals and will be extinguished while the breaker is tripped.
The cheapest breakers are thermally activated using bimetallic contacts and reset after cooling. If the short still exists they will continue to recycle. Others are magnetically operated and usually recycle more rapidly. Both can be applied to AC or DC. Electronic crowbar breakers usually provide a very small or pulsing voltage to detect when the short is removed. Some breakers utilize a manual pushbutton reset.
All breakers are rated in amperes and are selected to prevent damage, however most are rated too high to protect a stalled motor.
A more extensive test uses a large wattage rheostat in series with an ammeter to measure the actual break current. Our TEST PANEL includes one for AC and another for DC. In general this may appear to be just impressive, but to the knowledgeable it is very useful to discover faulty or failing breakers. Used and older packs should be evaluated using these. Occasionally new packs turn up with bad breakers, usually the Hong Kong specials.
CAVEAT: For safety's sake,
breakers should be checked periodically!
Checking the voltage at rated current is another test performed in a similar manner, but with a voltmeter across the load resistor. Most should yield at least 12 V at the rated value. With VA rating, the current can be found by dividing the voltage into VA. Older DC packs with selenium rectifiers tend to age; reducing output voltage due to increased resistance.
Other more subjective tests are to check the throttle for smooth variation in voltage as knob is turned. Broken and loose windings or a bad contact can be rapidly detected using a light bulb or voltmeter across output.
The final test is: how well does it work for your intended purpose? With or without pulses, all throttle controls should provide good starting, stopping and operation throughout the entire range of desired speeds. Although, compared to FLYWHEELS, power packs produce far superior momentum; they vary in characteristics and many are not adjustable. Regulation or the ability to maintain constant speeds may be important. Shifting or switching throttles should have good low speed control, probably without momentum. The choices are yours; you are the brass hat.
BACK TO OUR TEST EQUIPMENT
POWER PACKS OR TRANSFORMERS?
For AC applications TRANSFORMERS are used to change voltages. These are electro-magnetic devices consisting of a primary (input) and a secondary (output) coil of wire wound on a soft iron core. As with old Lionel models, some have tapped secondaries to permit voltage selection. Others have wipers similar to wire wound potentiometers or rheostats, mostly on the secondary. Simple transformers of the correct voltage are the most economical power sources for incandescent lights on the layout. For dimming, an old Lionel variable transformer is excellent. Only DC should be used for LED's.
DC POWER PACKS are more complicated since they contain rectifiers to change AC to DC and various means to control track voltage. Not all contain transformers, some use switching power supplies.
BACK TO TIPS ON TESTING
