This time I'm writing about the above power pack. I have read, in various places on the 'net, about how the "Accutec" feature of these packs was all hype or a marketing gimmick. The feature is supposed to keep the current to the locomotive(s) constant regardless of load from other devices, like lights, etc. so the train doesn't slow down or can go upgrade without stalling. To test it, I first ran a train with an older Tech II pack and threw a switch while it was running. The train slowed down as long as the switch controller was activated. I tried both a typical single Atlas N scale switch and also, two Atlas under table machines (roughly the equivalent of the old Atlas HO machines) thrown at one time in a crossover. I then tried the same thing with a Tech 4 260. The speed of the train was not affected at all while the switch was thrown. This demonstrated to me that the circuitry IS regulated and keeps current constant. Doug
If I were to guess, and a guess is all I can do as I don't have either of these to pull apart I would guess there is 2 ways to achieve this result. The first is to have 2 transformers in the pack that provides functions to both the accessory circuit and one to the tracks. This would then prevent one from effecting the other unless things really went bad. The other way is to use a high quality switching power supply for the track and a center tapped transformer to supply for the accessory side. The switching power supply would get it's feed from the same transformer but as the regulation is based on 3 or 4 transistors instead of capacitors, the reaction to current changes is almost completely invisible to us slow humans. It would be interesting to see which method they used.
It's funny but I don't think I have ever had either one of my 4's open. The accepted explanation is that they have a feedback circuit which detects the increased load and instantaneously increases the current output, thus compensating for the increased load. This would be different from just a regulated output which would be able to maintain a constant current output but only to a maximum and then the output would sag if that was exceeded. Doug
This is exactly how a switching power supply works. The current is regulated by switching transistors on and off, and when more current is needed the transistors responsible simply are biased on for a slightly longer period of time to give more current.
