Discussion in 'HO Scale Model Trains' started by john arisman, Dec 31, 2006.

  1. john arisman

    john arisman New Member

    I need to replace the wiring for the light in my son's FA7 ho gauge diesel. Can anyone please tell me how to do this and what I will need as far as wire and a light. Do I need to use any resistors to create a ground? Thanks for your help.

  2. steamhead

    steamhead Active Member

    First of all, WELCOME TO THE GAUGE...!!! You'll find all the folks here more than willing to share their expertise (or lack thereof, in my case...) with you.

    Sounds to me like you haven't opened the locomotive yet. When you do, you should first determine if you've got a light bulb or a LED in there. If it's a "starter set" loco you probably have a bulb. In any event, all you need to do is remove (cut or unsolder) the offending bulb and replace with another one. If it's a LED, be careful to maintain the correct polarity or you'll blow it out first time you give it the juice.
    Hope this helps.
  3. steamhead

    steamhead Active Member

    See what I mean...??? You're asking about the WIRING and I focused on the bulb :oops: ...Is the wiring damaged in some way??? Do you suspect the wiring is damaged because the bulb won't light??? Check the bulb first. If it's OK, then there is something wrong with the wiring. It could be something as simple as a false or broken solder joint. In all my born days (and they're more than I care to count...) I haven't had to replace ANY wiring for any reason. If you do need to replace it, make a schematic of what is in there, and just duplicate it.
  4. john arisman

    john arisman New Member

    I have opened the locomotive and the solder joints do appear to be intact. I will make a schematic and hopefully be able to replace it all. Thanks for the help.
  5. steamhead

    steamhead Active Member


    Do you have a "multimeter"?? It's a MUST (well, almost...) if you're serious about MR'ing. If you don't, you can get an OK one at Radio Shack. It'll help you track (pun intended) down electrical problems without having to go snooping about trying to figure out what is wrong. If you can afford it, get the "Analog" (with an indicating needle) instead of the digital LCD ones. They can save you a lot of time & frustration...
    Good luck...!!!:thumb:
  6. Triplex

    Triplex Active Member

    Do you mean an F7A? What brand is it? Can you post a picture of the engine with its shell off?

    (Disclaimer: I'm not an expert with locomotive repair. However, I know that not all locomotives are assembled at all the same, and recommended repair procedures vary from model to model, so an identification will probably be helpful to someone else here. :D)
  7. Relic

    Relic Member

    Why do you favor the analog multi-meter? Does the led types give a false reading?
  8. pgandw

    pgandw Active Member

    My reasons for preferring analog multimeters are:

    - digital meters can give a false sense of accuracy. Analog meters have the inaccuracies of the measurement plus reading the needle scale. Digital meters have the measurement inaccuracy plus digitization errors, but display a number of digits indicating great precision anyway.

    - analog meters show a slow pulsing voltage - such as the flashers on a car - much more intuitively than a digital meter

    - if I choose the wrong scale or get the wrong polarity, I can see the needle peg on analog. With a decent digital multimeter, scale choosing and polarity compensation is automatic and I have less sense of what is really happening.

    These are really minor reasons, and might not even apply to you. Choose which you prefer.

    my thoughts, your choices
  9. Russ Bellinis

    Russ Bellinis Active Member

    I have both types, and I use both depending on what I want to check. As a couple of examples, I find the analog meter to be my preference for checking out capacitors. If I'm using an ohm scale to check for shorts or continuity, I prefer digital, but either will work fine. I think at Radio Shack you can get one of each for less than $20-$30 total.

    This post is just for general information, since you have posted a plan to draw up a schematic and post it here, I would presume you are not totally "green" electrically. One caution I would offer is that some of the better quality ho scale locomotives have directional lighting and lighting packages. Some will use led's for lights, others use "grain of wheat or grain of rice" bulbs (really small). The led's will operate on 1.5 volts, the miniature bulbs may operate on 12-15 volts, 3 volts, or 1.5 volts. You generally can't tell by looking at a bulb what voltage it is designed to run on. If you have a "lighting package", it will have resistors and transistors on the board to turn on bulbs and reduce the voltage if the bulbs are lower voltage than the track voltage. You will need to determine what voltage is going to the lights to determine which bulb to get to replace it.
  10. Relic

    Relic Member

    if you were replacing the stock bulb in an athrean deisel,with a" grain of "would you go for the low voltage? do the low voltage ones need some type of resister to keep 'em from blowing at 15 volts? and lastly,will the 12 v bulbs steel enough power to alter power/speed of the unit?

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