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Re: Resistance Leak from Fast Track turnouts

Tom O'Hara
 

I'll echo what Gary says. I don't see any way that current gets from top to bottom copper unless a bit of solder crossed the gap or something else (??). Then the resistance would be tiny and an easy path from top to bottom, and there would be a definite short circuit. Does the substrate conduct? It shouldn't, as proved by zillions of pc boards in use. Can you decompose it? I doubt it, but I guess that's a (unlikely) possibility. Incidentally, if you check for continuity with a checker, there should be no connection.

I'll also echo the soldering technique. Heat the rail with your iron, not the pc tie. You may have to touch the tie for a moment, but that is all. The copper foil can peal off the substrate with too much heat.

I have installed hundreds of pc ties. Each time that I have had continuity where I didn't want it, I have found a metal bridge where I shouldn't have had one. Once removed, the continuity was zero and the resistance infinite.

...Tom

On Mon, Mar 2, 2020 at 7:16 AM Gary Chudzinski <chudgr@...> wrote:
Richard Sutcliffe writes:
Both cases there was a very high resistance short, just a tiny leak of current.
I’m sure many can relate to the term resistance leak.

Dick,

For me, the term, resistance leak, is somewhat confusing!  How does resistance leak?  I think current leak better identifies the problem you describe!  Also, as one that has built many turnouts in S gauge, I don't see how applied heat during assembly could reduce the insulation  between the top and bottom foils to the point that they could come close to touching, unless the person uses excessive heat from the solder iron, or the CB ties are much thinner than Fast Tacks ties.  Forty to fifty Watt irons are sufficient to get a good flow of solder.  Further, the majority of heat should be applied to the rail base rather than the CB foil.  So, perhaps the flaw is in the application of heat.  Again, the instructions are very clear and detailed on how to apply the flux and heat!  The small swabs are perfect for applying the right amount of flux to the ideal location!  Early on, Fast tracks sold acid flux with precise instructions on how to cleanup.  However, resin flux is now a better option!  I'm wondering if acid flux was used and broke down the CB insulation material causing the high resistance short??

Gary Chudzinski











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... Tom
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