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dhoadley

Nova II installation

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dhoadley

I'm changing to a Nova II ignition module in a small, old Briggs with a plunger type condenser. The hookup just looks too simple! Splice the wire to the coil and mount? How does that tiny thing know when to spark? and where have others mounted the module, outside on a shroud?

Thanx, Dave

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BLT

It does work good and it doesn't wear out. Just remember if it doesn't work one way, flip the wires. Also leave points in place so plunger keeps the oil out. I bought a 7010 twenty or so years ago, installed a Stens unit, sold the tractor and as far as I know it's still running on it.

As far as knowing what it does, it's explained here. All that stuff packed in a cube not much thicker ten three quarters.:D

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DanD

Most people report very good luck with these ignition modules. I tried one on my 7016 because the points plunger and bushing were worn and I'd get oil on the points even with a good seal on the plunger. However, the engine would miss terribly at higher speeds. Ran fine at idle and just above, but the faster it ran, the worse it got. So I just took the bull by the horns and replaced the plunger and bushing and put on another new seal. Filed the points again and adjusted the gap and haven't looked at them for about 8 years (this tractor doesn't get a lot of hours but is still running perfectly.)

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powerking_one

Actually the video BLT references on how these Mega-Fire and Nova-II type devices work is not even close. I dissected one years ago and it is basically $1.00 worth of parts; 2 transistors and 1 resistor. They can only approximate the correct ignition timing in that when the magnets pass over the coil the rise in voltage between the 2 wires(primary) turns on the transistors (hard) which is close to a short circuit (AKA like points closing). There is no precise "trigger" timing using this type of device, but yes they generally work well. Most modern solid state one piece molded ignition modules have this type of setup inside.

Tom (PK)

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fishnwiz
quote:Originally posted by powerking_one

Actually the video BLT references on how these Mega-Fire and Nova-II type devices work is not even close. I dissected one years ago and it is basically $1.00 worth of parts; 2 transistors and 1 resistor. They can only approximate the correct ignition timing in that when the magnets pass over the coil the rise in voltage between the 2 wires(primary) turns on the transistors (hard) which is close to a short circuit (AKA like points closing). There is no precise "trigger" timing using this type of device, but yes they generally work well. Most modern solid state one piece molded ignition modules have this type of setup inside. Tom (PK)


id="quote">
id="quote">Wish I would have thought about this idea! $$$$$

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GrincheyOne
quote:Originally posted by BLT

PK was right about not even being close but that is all I had. I did however find that patent drawing that Sten's got for then Mega-Fire so Tom can better explain it's function.http://patentimages.storage.googleapis.com/pages/US5058543-1.png


id="quote">
id="quote">I see the schematic shows two SCRs and two capacitors.I guess the eyes, really the 1st thing to go! Lost count, and it's been decades since I had to decipher schematics. However I seem to detect at least two RC oscillator circuits. The variable resistor in the one circuit, is likely there for the patent application, and was replaced later in production with a fixed value.I think I inherited one of these along with the B&S 14HP engine I bought from RayS (a coupla years ago).

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joelk

As far as where to put it, I found taking the points out and just putting a screw into the plunger hole (to stop oil leak) and mounting under the cover works well. That way my wires are tucked away pretty well. They do work great, no more getting points wet when washing our outside in the rain. Had one set in for at least 10 years, no problems.

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EDS

On " How does that tiny thing know when to spark? ", I suspect that it has to do with the reversal of the magnetic field as the flywheel rotates. There are NORTH and South magnetic Poles on the flywheel. The voltage induced in the coil is either a positive pulse followed by a negative pulse or a negative pulse followed by a positive. The transistor will switch with only one of these configurations. That is why if the Nova II or Magnetron don't work, we need to reverse the wires or for the Briggs Magnatron, send the flywheel back to have the magnets re-magnetized in the opposite sence. The point of the field reversal or spark can assume to be in the center of the space between the magnetic poles.

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johnmonkey

I wonder if you can replace the a three leg coil (used on the 19d B&S engine) and get a megafire to work on a 19d? ....I suppose you would need to replace the flywheel as well???Just wondering if anyone has tried it? Thanks, JH

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BLT
quote:Originally posted by johnmonkey

I wonder if you can replace the a three leg coil (used on the 19d B&S engine) and get a megafire to work on a 19d? ....I suppose you would need to replace the flywheel as well???Just wondering if anyone has tried it? Thanks, JH


id="quote">
id="quote">Unless your coil is shot, you should be able to use it by disconnecting condenser wire and connecting it to Nova module and there is an extra wire on Nova to reverse polarity if needed.directions_1.jpgnovainst.gif

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msiebern

It is my understanding that since the Nova II style ignitions are triggered by the magnets passing by the coil, they will fire every revolution instead of every other as with points timed off of the cam. The majority of people have no problem after installing the Electronic modules, but I have had 2 instances where it would fire on the exhaust stroke when trying to start, sometimes leading to a blown head gasket.

Someone had posted on here that they ran their ignition module through the points, eliminating this firing during the exhaust stroke. (You do eliminate the condenser in this process) You don't have to be real precise with the points setting, but get them as close as possible. Once I did this, they started the first crank over every time and no backfiring.

Just my experience and thanks to whoever posted about routing it through the points.

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BLT
quote:Originally posted by msiebern

Someone had posted on here that they ran their ignition module through the points, eliminating this firing during the exhaust stroke. (You do eliminate the condenser in this process) You don't have to be real precise with the points setting, but get them as close as possible. Once I did this, they started the first crank over every time and no backfiring.Just my experience and thanks to whoever posted about routing it through the points.


id="quote">
id="quote">Guilty, I think. When I first joined in '99 I had mentioned that but some guys thought I had bats in the belfry. But like you say it worked.:D

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