RailPro > Finished RailPro Installation Examples

Installing a TCS KA3 or KA4 on an LM-3S without a bridge rectifer

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Alan:
Ha! Proof that all electronics are indeed smoke powered. Why else would they quit working when they lose their smoke?

Installing with a bridge rectifier does preserve the protection of the light outputs. Not because of the bridge itself but rather the fact the bridge and KA are attached upstream of the built-in module protection. Installing a KA using the blue wire and ground pin places the KA downstream of the built-in protection thus rendering the protection useless. It is only a problem if a short circuit occurs on one of the light outputs. Otherwise, it is fine.

You hit the two main differences - piece count and warranty. Although, as has been mentioned before, there is no way Ring could determine that a KA killed the module so the warranty issue is more one of your own personal morals. I once bought a new Walthers turnout only to open the package and discover a used piece inside. Clearly not every model railroader takes the high road.

Kevin has conformed that a bridge rectifier installation may require a touch more throttle to get moving than a non-bridge installation. Given that every layout has a different level of electrical integrity you may or may not notice this effect. There should be a slight reduction in top speed as well however if you do experience a difference it will be very small.

There are some very small bridge rectifiers available if space is a problem.

jimw:
Alan, I am puzzled as to why the addition of a bridge rectifier to the light (blue) common would result in a voltage drop to the motor circuit?  Was Kevin's installation different from Bill's diagram above?

Please excuse my ignorance if this is a stupid question. My brain circuits for electronics are obsolescent, since they were wired 40 years ago!

Alan:
The rectifier is attached to the red and black wires (power from the rails).

jimw:
Thank you, Alan. That clarifies my misperception.  Am I correct in assuming that the capacitor (KA) as diagrammed will only provide relief from light flicker, but not sound or motor?

Jim

Alan:
Definitely will stop light flicker. For motor and sound we can't say for sure without knowing the internal circuitry of a LM3. It may, it may not. Bill and Kevin's experience can shed some light.

The rectifier/cap on red black scheme will provide temporary power to motor, sound, and lights.

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