Thursday, 24 July 2014

Turnout problem continues

Its all about resistance or is it capacitance

Per my earlier post, Im still having issues with the hand built turnouts and block detection.

I also posted a question on the RailWire Forum to seek help there also.
http://www.therailwire.net/forum/index.php?topic=33418.0

I changed the detection threashold on the BDL's to high / 10K with little change to the issue.

I then did some testing and I think I have found the problem.. But the solution eludes me for the moment.

I tested 4 newly cut copper ties and found the gaps to be all open circuit.
I then just placed the tie in the Fast Tracks jig as I would normally do and added a dab of flux..

BINGO.. The tie now is no longer open circuit and now has resistance across the gap. I think the flux is wiking into the fiberglass tie and is causing it to conduct.. All be it with a high resistance.

Here is the flux I am using..

Here is an example of a meter reading.. It is important to note that each join gives a different reading.

I have not tried to clean the tie as yet.. I have just applied the flux and let it dry..

Now to find the bext way to clean the flux off and then find a way to apply it to the built turnouts..

Thanks for checking in.

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2 comments:

  1. Ron McF24 July 2014 at 17:17

    Can't help thinkin' if all else fails, read the instructions..

    "(4) Remove flux residue with water." LOL

    Jaycar sells a product called Circuit Board Cleaner (http://www.jaycar.com.au/productView.asp?ID=NA1008). I notice that in their product description, Jaycar says "many circuit problems occur when flux and other contaminents (even finger prints) remain on the PCB causing 'leakage' between tracks".

    I doubt that they meant RAILROAD "tracks" but the message is the same. I have a can of this and it seems to work a treat.

    Regards,
    Ron

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  2. Rod Warren24 July 2014 at 19:23

    Brendan
    When I modified all 108 of turnouts back in 2003 / 4 I did not use a liquid flux. I used resin cored solder and never had an issue such as you. Then I used Carrs Green label flux available from Brunell and no spray.
    On those that I have fail during ops sessions I use flux from Brunell models, sprayed with the same stuff Ron is referring to and it does not seem to have caused any issues and you know how many I have done.
    Move away from that flux and purchase the best rosin cored solder you can.
    Rod.

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