Ballast resistor or no ballast resistor

[RJRENTON]

On the stock ECU, the 5-pin module used the dual ballast resistor with the 5-Ohm section feeding into the fifth pin which connected to a Zener diode inside the box to create a voltage regulator for the ECU. The latter 4-pin ECUs just put the 5-Ohm power resistor inside the ECU. I don't know about the Rev-N-ator if it uses the fifth pin?
https://www.electronics-tutorials.ws/diode/diode_7.html

Not totally correct. There's no zener diode connected to the.5th pin but a complex voltage divider network. On the later 4 pin ECU, the circuit was redesigned using a resistor/capacitor/transistor network including a programmable SCR to furnish the dwell function as well as shaping the keying pulse to the external switching transistor on the outside of the ECU (which actually controls the coil's primary current) to cause the spark. Perhaps, you can show the two different ECU SCHEMATICS as an example of what you are saying......
BOB RENTON

 

[toolmanmike]

If you trust Rick Ehrenberg, the ballast resistor protects the ECU too.

In a way it does!

 

[Sinitro]

Take a ohm meter with the ballast resistor unplugged and measure the actual resistance across the terminals. You will need an accurate volt/ohm meter. Depending on actual ignition the typical ballast resistor is .3-.5 ohms. That's not much resistance but should cause some drop in voltage. If it's 0, then it's for appearance only.

Note that the amount of resistance of the ballast resistor changes depending upon its temperature...
Internally the ballast resistor uses nichrome wire which increases in ohms value as it heats up..

Just my $0.02...

 

[RJRENTON]

Note that the amount of resistance of the ballast resistor changes depending upon its temperature...
Internally the ballast resistor uses nichrome wire which increases in ohms value as it heats up..

Just my $0.02...

Only if it has a positive temperature coefficient. Nichrome wire can also have a negative temperature coefficient depending on design and the wire's alloy. Because it's a relatively low value of resistance (0.5 ohm to 0.8 ohm) to begin with, what is the percentage of change (10% - 50%) of value per degree of temperature change......it's not uniform.......
BOB RENTON

 

[Nacho-RT74]

On the stock ECU, the 5-pin module used the dual ballast resistor with the 5-Ohm section feeding into the fifth pin which connected to a Zener diode inside the box to create a voltage regulator for the ECU. The latter 4-pin ECUs just put the 5-Ohm power resistor inside the ECU. I don't know about the Rev-N-ator if it uses the fifth pin?
https://www.electronics-tutorials.ws/diode/diode_7.html

Rev-N-Nator ECU is 4 pins

 

[Sinitro]

Only if it has a positive temperature coefficient. Nichrome wire can also have a negative temperature coefficient depending on design and the wire's alloy. Because it's a relatively low value of resistance (0.5 ohm to 0.8 ohm) to begin with, what is the percentage of change (10% - 50%) of value per degree of temperature change......it's not uniform.......
BOB RENTON

BOB:
Keep in mind...
Nichrome is an alloy of primarily nickel and chromium, with variations available with different proportions for these elements.
As the temperature increases, its resistance does increase but..
Nichrome has a very low temperature coefficient compared to other metals,
so the end results are that its resistance changes vary relatively little with temperature...

Just my $0.02...

 

[RJRENTON]

BOB:
Keep in mind...
Nichrome is an alloy of primarily nickel and chromium, with variations available with different proportions for these elements.
As the temperature increases, its resistance does increase but..
Nichrome has a very low temperature coefficient compared to other metals,
so the end results are that its resistance changes vary relatively little with temperature...

Just my $0.02...

I'm well aware of nichrome wire and its composition......it's temperature coefficient is dependent on several aspects.....gauge of wire, length of wire, composition.....the term nichrome can apply to several alloys of nickel and chrome outside of the assumed 80%/20% common variety. I use to design parallel resistors in high voltage oil filled circuit breakers, that when, inserted as a voltage drop during the breakers interrupt phase, when the breaker was operating for fault clearing time.....the resistance prevents a restrike during opening and the wire was not the generic "nichrome" alloy.....it was a negative temperature coefficient alloy.....yes I'm very much aware of it's characteristics.
BOB RENTON