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LED Lighting Rectifiers

Bill models G scale and sent in this question:

“I am trying to utilize a KBP 307 rectifier to convert 15v ac to dc for LED light strip purchased from a train show vendor. When connected to my transformer the ac side shorts out and won’t light the strip. The strip does light on dc just fine. Followed ac + – markings on rectifier ( the out side leads one on each side, two dc leads in the middle. What am I doing wrong”

6 Responses to LED Lighting Rectifiers

  • Dale Arendssays:

    Keeping in mind that I haven’t used a KBP-307 but, from the spec sheet, it looks like the AC wires should connect to the two inner leads and the DC output is the two outside leads. So if your LED strip is designed for DC use, it should be connected to the outermost leads, watching the polarity of course.

  • geoffsays:

    I agree with Dale, the DC pins are on the outside, and AC on the inside. I don’t know if you can check the proper operation of the rectifier, if you connected it backwards it may be broken?

  • Anandasays:

    That bridge rectifier has the +ve pin at the end where the corner is cut off and the -ve pin is on the other corner. Like mentioned above, the middle pins are AC input.

    • Anandasays:

      By the way, if you just connect the bridge rectifier AC pins to the transformer and it is “shorting” that bridge might be faulty internally.


    One trick used by AC Gilbert American Flyer guys is to install a full wave bridge rectifier in the transformer. While the engine runs on AC, it also runs very nicely on DC. The hum is a lot less and very smooth operation. Check it out.

  • Kevin Chingsays:

    Hi Bill
    Just remember when AC is rectified the output voltage will be 1.4 times the output voltage as the AC voltage is rated as an average voltage of the sinewave so 15 voltas ac will be 21 volts DC this could be too high to run the LED’s All the type of bridge rectifiers that you state the inner pins are for connecting to the AC input.

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