SA electrical problems...final clarification needed

While you learned folks were discussing electrical circuits and so forth, I sorta got lost in the fog. So, I want to know exactly which order the ballast resistor is supposed to be in. I think I understand it to be as follows when using a 12 volt coil:

Battery wire to ballast resistor, resistor wire to + terminal on coil and then - coil wire to distributor.

Is this correct?

I originally thought the battery wire should go straight to the + coil post, then the - coil post to the ballast resistor and from the resistor to the distributor.

Thanks, once again.

Mark - Both locations for the ballast resistor you suggest will work.

Reason: The resistor, coil primary and distributor breaker points comprise a series circuit. The same current flows thru all 3 regardless of the order in which they are connected.

So you can wire the resistor in whichever location works best for you!

Votes right now on that issue are 2-1 in favor of the former.

They all three agree that the resistor will perform its intended function when inline between the battery and the coil.

The learned (and respected) heads are disagreeing over whether that's true if located between the coil and the distributor.

I'd go with what they agree on.

I'm voteing with the majority on this one, but I have one of my H's using a external ballast and sure am going to just hook it between coil and distributor just to see what happens. On another close related subject. Magnetos as used on these multi cylinder tractors do indeed have a distributor on them and therefore when distinguishing between Magneto and "battery igniton" I vote for calling them just that, Battery ignition units and not distributors.

I vote for the description you give. Jim

An interesting discussion here. From my electronics background, I'd like to weigh in with one point that is overlooked.

It is true, the resistor, coil primary, and breaker points form a series circuit and circuit current will be the same regardless of the order of components.

However, when the points open, the coil primary and the condenser then form another series circuit to "discharge" the energy in the coil primary, induce a high voltage in the coil secondary and create the spark at the plug.

The circuit designers match the capacitance value of the condenser with the inductance value of the coil to give the greatest efficiency to the coil primary/condenser series circuit and hence the hottest spark.

In theory, to add a resistor in the coil primary/condenser series circuit will in effect create a defective condenser and reduce the circuit efficiency and hence the spark.

So, as far as the placement of the resistor in the circuit, the points don't care, but the condenser does.

The reason the circuit will operate with the resistor between coil and distributor is that the resistance of the resistor is very low, probably less than 2 ohms.

This is my reasoning why the resistor is properly placed between the switch and the coil and not the coil and distributor.

I don't have a tractor with resistor to experiment so would be curious to hear the results if anyone can experiment with the actual placement of the resistor.

Bob

Bless ya, Pete! ;8^)

And let us know how ya make out with that resistor.

Bob - You bring up a good point!

Locating the resistor BETWEEN the coil and the condensor increases the value of the "R" in RLC circuit that is the coil primary circuit. And that theortically changes the coil's magnetic field collapse rate and hence output spark energy.

However from a practical standpoint the addition of the ballast resistance (~2 ohms or so) between the coil and condenser doesn't make a signficant reduction in spark output - at least no difference that can be discerned on a slow- reving, low compression tractor engine.

Incidentally I've run 12 volt conversions with the ballast resistor in both possible locations - have never noticed any difference between the two.

As previously discussed I RECOMMEND YOU WIRE IT AS FOLL0WS:

Ignition IGN output switch to Ballast Input.

Ballast Output to Coils Input (+ if Neg Ground,
- if Pos Ground)

Coils Output (- if Neg Ground, + if Pos Ground)
to Distributor

IE BALLAST GOES AFTER IGN AND BEFORE COIL NOT
BETWEEN COIL AND DISTRIBUTOR

I CAN NOT IN GOOD FAITH RECOMMEND YOU PLACE THE
BALLAST BETWEEN THE COIL AND DISTRIBUTOR, SORRY

Fun discussion, hey IT WILL WORK EITEHR WAY

BUT

I HAVE NEVERRRRRRRRR seen a ballast placed
between coil and distributor on these old
points and coil ignitions I REPEAT NEVER...
Somewhere I once read some info with scope
traces explaining the ringing oscillation that
took place between the coils primary and
condensor in that primrily LC circuit and
a discussion of that energy transfer which,
by the way, allows for more spark energy then
if a condensor isnt used.

Dont forget, Im NOTTTTT talking about solid
state electronic ignition that doesnt use
points in paralell with a condensor.

So, there you have it its your tractor do as you please (then maybe I can see the first one with ballast between coil and distributor lol) and YES it will still work. Unless and until a true bona fide Kettering Ignition Expert can convince me (and it takes MORE then a paragraph here) it should go between coil and distributor.

Thats my story and by golly Ima stickin to it, so its your tractor now feel free to wire it as you see fit and choose whom you decide to go with, hey its still a free country (Unless Socialism takes over as many seem to desire). I will continue to recomemend what I believe is best......I am here to try and help NOT do harm

God Bless yall here regardles of your opinions on this, its a fun discussion I thoroughlly enjoyed among great friends and other fine gents

Ol John T BSEE, JD

GREAT POST, THANKS I ENJOYED IT

I just gotta dig to see if I can find that article with scope traces and info about the ringing oscillation and energy transfer between the condensor and coils primary and an explanation of why the spark is greater then if no condensor was there.

Of course, if the condensor is too big, theres NO spark, you dont get the fast enough collapse of the coils magnetic field CONVERSELY if its too small theres still a spark, albeit it weaker (plus points burn up fast). The rating of the condensor and inductance of the coil is precisely matched to achieve max spark energy (and prolong points life) (has to do with the time constant and the rate the magnetic filed collapse) and that LC circuit to me is different if the energy suckin/wasting ballast is located BETWEEN coil and points/condensor which changes the whole RLC circuit dynamics and the magnetic field collapse rate.....

BY GOLLY IM STILL RECOMMENDING ITS PLACEMENT BEFORE THE COIL heck even if it dont matter, Im an old fuddy duddy conservative and alwayssssssss seen them placed there and plan to continue the tradtion

GREAT DISCUSSION, THANKS

Ol John T

Gee Scotty, I wasnt aware this Board has "learned and respected heads" who are they, lets tar n feather them n run em out of town lol Youre tough as nails on this tricity stuff yourself and Im tooooo old for this I graduated BSEE Purdue way back in 69 and forgot most of what little I learned then,,,,,,,,

Isnt this a fun chat wooooo hoooooooo

Ol John T

How'd ya make out on yer alternator, by the bye? Did ya have it checked out?

I should hasten to add, out of respect for JMOR's position, that counting votes isn't the determining factor. I'm just advocating putting the reisistor where everyone agrees that it does work. That, and, depending on the design of the resistor, you might just find a place to bolt it down along the way, so you don't have all that wire dangling along there.

You fellers have convinced me of one thing:

I should have been Talk Show host.....hehehe!

This subject has created one of the most lively and well behaved discussions I have had the privilege to follow.

For starters....I know it will work if between the coil and distributor because that is how I wired it up!!!!!!

But then I got worried that I had done it wrong and so I came back to ask again.

So, without further adieu I will ask this question:

Just what does the ballast resistor do in the first place, requiring it in the circuit? You see, in my uneducated mind, I thought that the 12 volts being sent to the coil....and then I assume coming out of the coil....was too high for the points (burn them). So, the ballast resistor is added to step the voltage down in order to save the points. See how dumb I am?

So, if you folks can explain to me why the resistor is there to begin with...which should explain why (it goes before or after the coil) and will allow me to sleep better tonight!

Scotty, no I haven"t touched the alternator yet. Me and that red tractor are taking a break from each other for a few days.

You're on the right track. The resistor drops the 12v of the rest of the tractor's system to 6v to make it compatible with a 6v coil (or a 12v coil which requires a ballast resistor, which I think John pointed out is exactly the same thing). That's it's sole purpose on our tractors.

The 12v coil that does not require the resistor, as I described the other night, deals with the extra voltage by being wound differently internally so that its spark output and interaction with the condenser are the same as the 6v coil.

(quoted from post at 18:02:37 11/06/09) You fellers have convinced me of one thing:

I should have been Talk Show host.....hehehe!

This subject has created one of the most lively and well behaved discussions I have had the privilege to follow.

For starters....I know it will work if between the coil and distributor because that is how I wired it up!!!!!!

But then I got worried that I had done it wrong and so I came back to ask again.

So, without further adieu I will ask this question:

Just what does the ballast resistor do in the first place, requiring it in the circuit? You see, in my uneducated mind, I thought that the 12 volts being sent to the coil....and then I assume coming out of the coil....was too high for the points (burn them). So, the ballast resistor is added to step the voltage down in order to save the points. See how dumb I am?

So, if you folks can explain to me why the resistor is there to begin with...which should explain why (it goes before or after the coil) and will allow me to sleep better tonight!

Scotty, no I haven"t touched the alternator yet. Me and that red tractor are taking a break from each other for a few days.

Click to expand...

Actually, Mark, the coil doesn't give a rat's patotie about the voltage applied, what it cares about is the current thru it (energy= 1/2 L X I*2). The ballast resistor would best be described as a 'current limiting' resistor than as a '12v to 6v converting' resistor. Another observation for the doubting Thomases: When you buy a "true 12v coil", the resistance is built-in.....now, think about where that is in the primary circuit with the points and condenser.
Now, I brought all this up, just because I hate to see 'stuff' propagated that truly has no scientific/engineering basis, but 'it has just always been that way'. Same goes for 'don't sit that battery on concrete or the ground, or it will suck the juice out of it", or 'observe the coil polarity or else you lose 25%, 45%, pick your own % of the voltage/energy (pick that too)'. For myself, all of mine have the ballast between the ign switch and the coil. Why? Because the wiring is much shorter & neater that way. I observe convention with coil polarity, too. Why? Because that's the way they came from the factory. I also keep "stock" size tires on all my tractors and other vehicles, too. I like "original". I just don't like stuff done for all the wrong reasons. Take the front mount Ford distributors....when those tractors are switched to neg ground (usually due to 12v alternators), they have virtually no choice but to have a POS spark vs the original NEG spark polarity. If they could reverse the wires on that coil, they could gain the 'thermionic emission' benefit of a neg spark, but due to the internal primary/secondary coil connections (which they can not change), at the same time lose about 200volts of spark voltage, as result of add/subtract of primary/secondary voltage. So, what do ya want extra 200v or neg polarity? Neither matter.
As gentleman John T said, "God Bless yall here regardles of your opinions on this, its a fun discussion I thoroughlly enjoyed among great friends and other fine gents " AND I thoroughly second that! Some of such forum discussions turn to personal attacks and just plain nasty, and that this hasn't done so is a real attribute to this bunch of red power gentlemen!

When we all get done with you youre gonna be smarter then any one of us lol

PS youre NOT dumb, youre smart enough to ask good questions and your recent education paid off because your analysis above is fine.....

So, you ask, what does a ballast do ?? I bet I can answer that and allllllll here will agree (maybe lol)

OKAY lets start with the limiting factor of how many amps a set of points can switch without them burning up too fast AND THATS IN THE RANGE OF AROUND 4 AMPS. I like JMOR's discussion that its more of a current limiter actually, although, in so doing, yes it drops voltage SO THE POINTS DONT HAVE TO SWITCH MUCH OVER 4 AMPS MAX

NOW a 6 volt coil has around 1.5 to under 2 ohms primary resistance so when hooked on a 6 volt tractor it and the points handle around 6/1.5 = 4 amps.....On a 12 volt coil its resistance is more like 3 to 4 ohms so it sees 12/3 = 4 amps.....

BUTTTTT if you use a 6 volt coil on a 12 volt tractor AND DID NOT USE A BALLAST the coil and points current would be 8 amps and the points fry quickly plus the coil overheat and burn up NOW YOU GET THE IDEA WHY A BALLAST IS USED??????? Not only does it drop 6 volts leaving only the remaining 6 volts across a 6 volt coil but IT REDUCES THE CURRENT so the poinst switch ONLY 4 amps

ALSO "most" 12 volt coils used on these 40's to 60's farm tractors that people around here refer to as "internally ballasted" actually DO NOT have a seperate discrete "resistor" stuck inside that round metal can somewhere, tehy ahve more primary resistANCE DUE SIMPLY TO MORE LENGTH OF WIRE OR HIGHER RESISTANCE WIRE

Now post a picture of that ballast between the coil and distributor so I cant any longer claim IVE NEVER SEEN ONE THERE LOL buttttttttt my out is I was referring to any ORIGINAL SET UP. Its hard to catch an attorney in a fib remember !!! We have all sorts of limiting qualifying weasel worded hedge your bet responses. When thay asked nnalert Clinton if she knew about those Rose Law Firm records they discovered in the White Househer answer instead of yes or no was something like "I dont think you will find any evidence of that" see why politicians are lawyers ??????

John T Engineer and Country Lawyer