Trembler coils output

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Model T Ford Forum: Forum 2012: Trembler coils output
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Thursday, August 02, 2012 - 04:54 pm:

I use the excellent strobo-spark to refurbish coils it performs absolutely excellently. I understand from previous posts the spark gap on the strobo-spark display is set to 1/4" and I agree that a good coil should jump this gap with no problem. However I have built up a number of coils now where the secondary and primary resistance measure fine, correct new capacitor fitted, new points set up correctly but they dont quite jump the Strobo-spark 1/4" gap. What else in the coil would cause this issue, and is there anything that can be done or are the coils doomed?

Many thanks John (Aylesbury, United Kingdom)


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Thursday, August 02, 2012 - 06:25 pm:

The coils very likely are arcing internally when presented with 1/4" gap to jump. You can confirm this by setting up the coils with an external gap of say 1/8" and then widening the gap a little at a time. You will very likely notice that when presented with the wider gap, the coil stops firing externally and begins to fire inside of itself. There really is no way to find out where it is arcing internally since it could even be between windings and the cause of this is usually that in the past the coil has been powered up but with no suitable gap connected so the coil then sparked inside itself. That internal arcing will lay down a carbon trail and the coil then finds it easy to arc at that point rather than the gap of 1/4". Unfortunately it is not uncommon on coils to find this.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cameron Whitaker on Thursday, August 02, 2012 - 06:44 pm:

As John said, there can certainly be a gap inside the coils that is smaller than 1/4".

There is also the chance that the insulation is shot inside the coil windings, or there is moisture in the insulation. Either problem could be present either individually or together, but unfortunately, there is no real remedy for shot insulation. If there is moisture in the windings, you can try baking the coil (laying down flat in case the tar gets too soft) at about 150 degrees for an hour or so. Let the coils cool down, and if that fixes the problem, then you are set.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Friday, August 03, 2012 - 04:29 pm:

Thank you John / Cameron. I tried a varying lesser external gap as John mentioned and indeed the coils fire but all much less than 1/4". Thanks for the explanation which confirms what I was also thinking. I can now lay these particular coils to rest :-(

John


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