Why Neg. Ground vs. Pos. Ground?

Back around '79, when I was nineteen and working in a transmission shop, a kid from school with a '65 Mustang put in his own radio, messed it up, burned the wiring under the dash (and almost the car because he was scared and viewing it from a distance) then towed the car to us for rewiring. Took me weeks to get it done when I wasn't doing other jobs, AND EVERY WIRE UNDER THE DASH WAS BLUE. I told him I never wanted to work on that car again.

 

Are you serious about this, or are you pulling our collective legs?

If serious, why does it work?

 

You question my sincerity, then ask for an explanation by asking ‘why‘ it works? Ha.
The short answer is, “Why” can’t be answered when related to physical science.

If you meant to ask ‘what’ occurs, or ‘what’ might be done to modify that occurrence, it‘s already been covered. Many different actions will result in changing the capacitance of a circuit. I have only pointed to two actions that a mechanic with limited resources can implement related to breaker point erosion caused by imbalance in the capacitor circuit. Beyond that, the discussion becomes moot.

 

WOW. Instead of using our wire stretching pliers to lengthen the capacitor leads, shouldn't we all get out our garlic plants to wave in the air, and start chanting? That would work just as well.

 

Something may be changed by lengthening or shortening the capacitor lead, but it is not the capacitance. You can change the charging time of a capacitive discharge circuit by adjusting the resistance of the circuit, but to simply change the length of the lead wouldn't make a substantial difference... unless that lead was really, really long.

 

Is this thread still going...

120 MEANINGLESS posts........

It really needs closing......

 

I thought as much. Pesky bugger, science.

 

Lead length affects inductance, and therefore the resonant frequency of the circuit. This is more likely be a factor in a cap used to supress ignition noise for a car radio than in a points ignition condensor. I still don't know why negative ground was chosen for the standard, and I have yet to lose any sleep over it.

 

Hey Nash, so by the time you figure out the right length wire, the engine is wore out and it's time to start over? Lippy

 

Conjecture on your part. You don't have a (practical) clue however............

I’m pointing out one last time that it works, even though any response should be unnecessary.
The information I have been passing on isn’t something I invented. It’s a practice carried on in days gone by, when the parts house was an hours drive from the barn. For some of you little boys that might not be able to wrap your brain around the concept of making do with what you have, listen up~! I know for a fact that the information is in an old SAE publication that I have. Problem is, I have boxes and boxes full of that kind of paper. I just ain‘t going to go digging for it. If you still don’t think it will work, but want to prove it won’t, get your ass out in the shop and try it. Some of you little boys embarrass me, to realize that supposedly hamb members in good standing, adult mechanics, you jump in and contradict something somebody says, without having a clue of practical experience on the specific point. Otherwise, please fuck-off. Please.
　
But, I’m not the only one in the whole wide world that knows the theory to be true. Here’s an excerpt from article I dug out of an article in IH tractor Club
It says basically what I have been relating.
Goodbye ya’all.

Excerpt from IH tractor club blog;
Contact pitting results from an out of balance condition in the system which causes the transfer of tungsten from one point to the other so that a tip builds up on one point and a pit on the other. The direction in which the tungsten is transferred gives an indication for correcting the situation. If the tungsten transfers from the negative to the positive point, one or two corrections may be made. Increase the capacity of the condenser, shorten the condenser lead, separate high and low tension leads between the coil and distributor or move these leads closer to the engine block. If the transfer is from the positive to negative point, reduce condenser capacity, move low and high leads closer together and/or away from the engine block, or lengthen condenser lead.

 

My practical clue, friend, comes from working extensively with electronics in a line control situation, utilizing AC drives, multiple PLC's, handbuilt specialty components, and other assorted "stuff" to deliver a product in an industrial environment. Reading comprehension is kinda important in what I used to do also, that "or" in the quote above makes all the difference in the world. Capacitance and discharge rate are two different creatures...my original point was that the capacity of the condensor had nothing to do with the length of the lead... the discharge time may be changed but the capacity will not.

Sorry if it felt like a personal attack on you, I just didn't agree with what you said, but don't worry, it'll be alright in the morning. I'll just add this to the ever growing pile of correspondence I like to refer to as "29nash trash".

 

There is no inductance in a capacitor. Inductance is an effect of electricity going through a coil. It is the relationship between the rise in rate of amperage in a coil as opposed by the counter emf generated in that coil by the change in rate.

EDIT: I was going to stay out of this conversation, but my good buddy couldn't help but be who he is. If anyone is interested in what's going on here electrically, I'd be willing to PM about it, with the exception of Mr. 29nash, 'cause, well, he already knows everything.

 

there is a minicule amount, but you are talking about such a small effect, you would have to be working on high speed IC circuits running at high frequencies, nothing that is going to cause an effect on the points in an old car. strange things happen at high frequencies. Where you have to worry about inductance is in your ignition coil, at high RPM's the coil starts to become saturated, the field can't collapse and the spark energy drops. They are finding out the old round coil really isn't very efficient, E style coils are much more resistant to these problems.

 

All I know is this:

Never argue about politics, religion, or electronics. The "Tron God" is the only one who really knows!
pigpen

 

I pulled the radio out tonight to get ready to paint the dash. I did some experimenting with positive versus negative ground using a battery charger for power. It has some buzz on bad channels in the 600 to 1000 range either way it's hooked up. The 1350 Rush Limbaugh channel works great on either polarity. It's the strongest channel in the area (of course). It appears that input power polarity on this particular AM tube radio makes no difference. Others may have problems, I don't know. I had a Volkswagon radio once that I put in a '55 Ford pickup. It would not work on the Ford positive ground system until I went inside it and reversed the input polarity. If I remember right, it was a transistor radio vice tube. The "Tron Gods" will make a fool of you every time if you're not careful! pigpen