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Blowing Transistor on Igntion Module

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boxchevyman

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Hello all!

First and foremost I’m not very savvy when it comes to circuitry so i thought you guys could possibly help me out.

I am building a CDI triggering mechanism that should collapse the ignition coil when the points open up. That’s the idea anyways; I got plans from this web site: **broken link removed**

So I went ahead and made this, and it works for a little while then blows the transistor. I put a new transistor on then it will work for half a minute just to blow again. I’m not sure the cause of this as my base voltage has a resistor on it.

I’m in over my head but do you guys see any obvious reason why this would happen?

Thanks for your time,

James

Here is a link what i have made, i cant figure out hot to post a picture: https://imgur.com/rtwdeSk
 
From "All About Circuits" in reply to my question about transistor grounding:
Hello, thanks for getting back with me. The wires leading from the heat sink and the transistor are grounded to the same point on the engine. Is that good enough?
Welcome to the forum. :)

Likely not. That can cause high voltage transients in the lead inductance due to the high currents being switched, which may be what's zapping the transistor.
Much better if the transistor is connected directly to the heat sink with short leads.
 
Pictures: Under "Upload a file". You may not have that privilege immediately.
==
Not too crazy over the construction technique.
Check for loose connections.
Make sure the distributer cap is gone.

I'm also going to point you here: https://www.electro-tech-online.com...gneto-internal-schematic.144306/#post-1216390 for a better construction technique.


I'd probably go with an entirely different design that what you have done.

Some ideas are to use pigtails of wire for the transistor with heat shrink on the ends. For now, you could put a pigtail on the resistor as well. It would be better than you have now.

Get the proper connector for the small pin. There is a thickness and a width.

I need to look for a better transistor for you.
This https://www.digikey.com/product-detail/en/BD13510STU/BD13510STU-ND/975638 might be better and suitable for DeBe's construction technique.

Find a way to mount the transistor close to the distributer.
The HEI module will have to be heatsinked. That means a light amount of heatsink grease and attached to a big piece of metal or a real heatsink.

I also want to take you here: **broken link removed** for the time being. I had an original XR700 on two vehicles.
 
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The pointless ignition system is for magneto type ignition systems. Not 12v coil & points systems.
 
This is a Bosch/ Ford Ign module beter suited to points conversion. Its main feature is if the points are closed & ign is on it automaticly reduces current draw. This is one of the draw back of the HEI module. Cant remember where I found this circuit. The module does need to be mounted on a heat sink & the heat sink also needs to be connected to the neg supply.
 

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  • FORD TFI MODULE For points.jpg
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High everybody,
Thanks for your help, I have been trying different ideas out over the past few days and i have ran into another roadblock. i bought a Ford TFI module in an attempt to just get this to work. and it ran for about 30 seconds and then i lost spark. i believe it has something to do with the module as when i check to see if i have continuance when i take the wire to ground and then off (simulating the points) i see an open circuit then ALOT of resistance. however when i flip the power off then on again and try the same test the module powers the coil on and off just fine for a short time.

I know you guys will point out the heat sink first thing but honestly im holding my hand on the back part and its not that hot, but im willing to listen. Also i wrapped the terminal ends with electrical tape so the terminals would not be connected.

Please see the you tube video to see what this does.
 
OK, not sure what to make of it yet, but take a look here: https://www.hotrodders.com/forum/duraspark-module-overheated-engine-died-225477.html

It does mention the coil/ballast resistor matching. In a normal points vehicle. the 12 V to the coil is powered through a low value resistor that in many cases was mounted on the firewall. Just during starting, that resistor was bypassed.

There is also an interesting construction technique as well.

EDIT: There is always the possibility that what you are doing causes the module to go into protect which requires a power recycle to fix.
 
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What coil are you using? A coil for the old points type ignition is not the same as the electronic ignition. The ohms/resistance is different, that may be what is smoking the drivers.
 
That's what I said essentially. At the very least, you have to keep the ballast resistor designed for the coil.

"Start(Ignition switch)" connects to the coil directly and "IGN(Ignition switch)" connects to the coil via the ballast resistor.
 
That's what I said essentially. At the very least, you have to keep the ballast resistor designed for the coil.

"Start(Ignition switch)" connects to the coil directly and "IGN(Ignition switch)" connects to the coil via the ballast resistor.

That's the way a Kettering style works. Electronic ignitions like the GM module and Ford don't use a ballast resistor. A direct 12V connection. The electronic ignition uses a low resistance coil when compared to the Kettering type. The higher resistance kept the points 'wiped' and except during starting operated at 6 - 8V. To keep the coil from overheating. The electronic modules also don't like to be run open circuit, with no plug in the leads.
 
Hey all,

OK so I returned the Ford TFI module and my local junk yard didn’t have the one with the heat sink, so I’m going to experiment with the HEI module. I hear what you all are saying about the points style coil. I Did buy a points style coil because it was cheaper.

I’m trying to figure out if it is indeed the coil’s fault. I have done some research on various forums and I’m getting mixed answers. Is there a definitive test that I could do to rule this as the source of the problem?

Thanks for your time,

James
 
I assume your working on a Chevy engine? Why not go to your junkyard and pull a HEI distributor and coil? To replace what your working with. Every Chevy engine from the end of the old stovebolt style straight6 up has a HEI style distributor available. The iron duke 4, 250 6, small and large block V8's all used them. But when using the HEI you MUST use the correct coil, NOT a points type coil. The link KISS gave is for a points type ignition don't add a ballast resistor, won't work.
 
Hey all,

I just wanted to pass on what worked for me. I soldered in a 2n4401 in place of the 2n222A and for some reason (You guys would probably know) its working much better. The only reason I’m am using that instead, is that it came bundled in the package I bought from RadioShack and had the same specs on their packaging.

So just wanted to say thanks for all the support I got here.
 
Have you considered a Ford Duraspark ignition module? I realize that replacement parts can be substituted once you break the BeO cover, at the risk of circuit board damage.
 
please ... never run a water cooled outboard without water ... the rubber impeller water pump in the lower leg will be destroyed in as little as 30 seconds ... and you are overheating the block / rings ...
 
A galvanized garbage can can work for small outboards. My experience was two-fold. My father fixed one or two for a friend and I broke a sheer pin when I was younger on a lake.
 
You can also get ear muff like suction cups to apply watering hose to skeg at water intake vents to avoid abrupt damage for outdoor use.
 
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