Repairing KW coils/capacitor voltage rating??

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Model T Ford Forum: Forum 2014: Repairing KW coils/capacitor voltage rating??
Top of pagePrevious messageNext messageBottom of page Link to this message  By Willie K Cordes on Monday, May 05, 2014 - 09:06 pm:

I have some capacitors for two or more years that have a voltage of 400V written on them and some with 600V.
I noticed that one of the catalogs are selling some that they call 1700V/uSec.
Are the lower voltage ratings useable or should I get the latest ones????
Any good suggestions would be appreciated.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Monday, May 05, 2014 - 09:44 pm:

I think you are comparing apples and oranges, or oranges and tangerines. 400V and 600V are steady state voltage ratings. 1700V/uSec is a transient voltage rating, or voltage impulse rating.

I would ask two questions:

Have you used either successfully in coils before?

I would be sure they are not aluminum electrolytics as they die as they get old.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willie K Cordes on Tuesday, May 06, 2014 - 10:57 am:

Ted, the capacitors with the 400V and 600V markings come from T part venders and the third one is listed in one of their catalogs.
They work, but I am concerned about for how long. It is not that easy to dig out that tar, replace the capacitor and pour tar back into the coil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, May 06, 2014 - 12:08 pm:

The flat ones that Fun Projects and Langs sell are the ones I prefer. They will be the correct dV/dT rating and they fit without having to move the glass. No more than capacitors cost, I'd throw away the round ones before digging out that extra tar. I pop the old condenser and wooden side off the coil, solder on the new capacitor and then replace the wooden side, then fill with tar. Very little digging required.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Tuesday, May 06, 2014 - 12:23 pm:

Willie
The 400V and 600V capacitors MAY or MAY NOT be correct. If you need help with the capacitors in question give me a call or send me photos of them and I can help.
Some "T part vendors" are selling an incorrect capacitor for use in Model T coil rebuilding.
Get the right part (with all the correct specifications) from Lang's or FunProjects.
Ron the Coilman
modeltcoils@windstream.net


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Wells on Tuesday, May 06, 2014 - 12:49 pm:

I needed something I could get instantly, so I installed the 400V " orange drops". They worked perfectly but, because the experts believe they may not last very long, I later switched to the 1700V ones that are recommended. Capacitors are cheap. It's not worth the risk to have anything but the best and by buying the good ones, you are sending the suppliers the right message.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willie K Cordes on Tuesday, May 06, 2014 - 01:53 pm:

Thanks, I will just order some more from Lang's as I have most of that order list made out.
Thanks


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Tuesday, May 06, 2014 - 02:06 pm:

Dave
It is important to remember "Orange Drop" is a trade name given to a complete product line of different type capacitors. There are many different specification Orange Drop capacitors and most of them are not appropriate for Model T coil rebuilding.
The most important thing is to NOT buy a capacitor with insufficient dV/dt (assuming other correct parameters) Unfortunately, many people who sell capacitors do not know about or understand that requirement.
The most common mistake people make is buying a small capacitor that easily fits inside the coil. These are commonly metalized Mylar type construction and will fail very quickly.
The correct capacitor sold by Lang's and FunProjects was specially selected for electrical specification and physical size to use in Model T coil rebuilding.
For all practical purposes, when correctly installed, they will last for another 90+ years.
Ron the Coilman


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