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Replacing condenser and cutout with modern equivalents


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I have received a couple of private messages about replacing the old wax paper condensers with modern mylar/poly capacitors and the generator cutout with a modern silicon diode. The parts stores I deal with in the greater Toronto area are what we used to have in Radio Shack stores. Radio Shack in Canada died about 15 years ago,maybe more, and were replaced with The Source stores which are basically more cell phone stores. All the parts for hobbyists went away. But if you are having questions about where to buy these parts now it would be at whatever electronics parts stores are around now in your area that sell the same lines as Radio Shack used to. SAYAL stores around southern Ontario sell all that and much more. I guess we are lucky to have them. They have rows and rows of resistors,capacitors,diodes,i.c.s,L.E.D.s,construction boxes,relays,power supplies,you name it. You can built any kind of project you want to just like we used to with Radio Shack. I know that the Radio Shack store in Watertown N.Y. does not have these parts anymore so I guess that would mean Radio Shack U.S. is out. But there must be stores around that have these parts. And the staff would help you with buying the right part/s.

A note about the condenser/capacitor in a distributor: The value of ALL the capacitors in ALL distributors from the Kettering system are virtually the same. They hover around .25 mfd/.22 mfd. This is because the coils were wound with the same inductance in Henrys. You know this because you can swap out a coil with any other 6 (or 12 volt coil) without having to know the Henry inductance value. Consequently the cap values match the coil inductance to tune the circuit. The circuit works best at low engine speed and starts to lower it's current output to the spark plugs at high speed. This was the one downfall of the Kettering system but the modern capacitive discharge system we have on all our vehicles now does away with this problem. Also the Kettering system on a good day put out 15 Kv,usually 10kv, and today we have around 100 Kv across our spark plug gaps. That's why the gaps is now 1/4" instead of .020". The breakdown voltage value of the cap really doesn't matter in the Kettering system. Any cap with a "wvdc" of 600 and above will work. I'm convinced that mylar and polycarbonate insulated capacitors will never short. I have never seen one do it and I've abused them something awful in higher voltage circuits that the manufacturers ever thought they would see. Using one of these in your old Kettering system from the 20s through to the 70s,when capacitor discharge systems came out, will do away with ever worrying about a shorted (leaky) old fashioned condenser.

The 1/4" stud mounted 50 amp silicon diode promises the same reliabilty. And it is mounted inside the Delco-Remy cover on the generator and no one is the wiser. (I believe in judging the judges are not allowed to remove covers.) The original cutouts have to have some reverse current going down to the generator to break the points holding on the relay. This can go on for some time discharging some of the charge stored in the battery. It is impossible with the diode. The battery nevers "sees" the generator windings. The diode also allows the generator to start putting current back into the battery before the cutout points would ever have closed. Also cars have been lost to fires over the years because of stuck cutout points. It was quite common. When you shut off the engine the cutout points are supposed to open and stop the battery from discharging through the now stopped generator. It did not always happen. The points stayed closed and the battery then started to discharge through the generator to ground and a greasy oily engine,or the wood floor, was the scene of the fire. A 50 amp diode,that is one capable of carrying 50 amps, will never short in a car/truck that has a generator only capable of producing 20 amps. cold. Less than that hot. And they get HOT. Ever touch your generator after a drive? Don't. You will burn yourself. This is why the cutout fails. It is cooked to death. The diode can take the heat. p.s. you should check your ammeter when you shut off your car to see if the meter is showing a large discharge. This will mean the cutout points have not released and you will are going to have a flat battery at the least or a fire at the worse.

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  • 1 year later...

DodgeKCL

 

This post was linked to a recent post in the AACA technical section. I'm interested in how you did the two conversions. Can you post photos of the parts used and then installed? Especially the generator cutout conversion?

Should the voltage rating of both parts match the system voltage? Am I limited to selecting for 6V components or is it okay to use a higher rated part IE a 12V part for a 6V system. ( such as this 250V rated .22uf  cap http://www.rpelectronics.com/my-0-022-250-5-0-22uf-250v-mylar-film-capacitor-pkg-4.html    )

 

Thanks

Brad

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