Chainsaw Repair

Thanks FPS,

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Ok very nice and good work.

I have a few questions.   First the pink on the schematic is that for the Oscilloscope probes.
Second does the 1 microfarad capacitor have a faster discharge time over the 2.2  microfarad cap and hence affecting the timing.

You might want to coat all your components in epoxy to protect them from moisture and oil.   

Could you go to a larger working voltage on the capacitor to prevent it from getting to hot when making long cuts.

Also did you wind the pulser coil your self.   

How high in the RPM's will this circuit be good for.    Like say up to 14,000 or more.   

Some great info and is good to know you can always come up with an ignition for an old saw.   
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I do not know of any schematics for ignitions that have limiting coils.    Besides those coils are all incased with epoxy and I doubt that you could get into one to modify it in any way.

If you could get into one of the newer limiting coils and since these ignition systems are solid state devices there is probably a component in there that could be changed so that the RPM range could be made to go higher.   
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I also noticed that in your first schematic at the end of your video you use a SCR to discharge the capacitor into the ignition coil.
On your second schematic you use two transistors to discharge the capacitor into the ignition coil.

Just two different ways to do the same thing or is there a reason that one is preferred over the other due to reliability or something else.

Also the first one looks to be much more simple in design than the second one.



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Very glad you gave much questions.


>1:
>the pink on the schematic is that for the Oscilloscope probes.

Yes it is. It's probes given by the schematic simulator. I have here on my desk top two of them, which are "LT-Spice" and "Tina".

>2:
>does the 1 micro farad capacitor have a faster discharge time over the 2.2  micro farad cap and hence affecting the timing.

Yes it does. The faster discharge time, the faster spin motor provides. This evidence is shown in my second video, where the larger capacitor disables higher spin to the motor.

>3:
>Could you go to a larger working voltage on the capacitor to prevent it from getting to hot when making long cuts.

Very good tip! I did not test yet but it's a nice point we should better try one!

>4:
>did you wind the pulser coil your self.

Yes I did, see this video too;
https://www.youtube.com/watch?v=9HAD9MKXbvQ

though this core is not that of Partner but from my lovely McCulloch 10-10!

>5:
>How high in the RPM's will this circuit be good for. Like say up to 14,000 or more.   

This is also a nice thing to test. From my experience this capacitor 1 Micro Farads may be a little too big for higher spin. Perhaps we should better choose smaller one like,,, say a half of it.

>6:
>I also noticed that in your first schematic at the end of your video you use a SCR to discharge the capacitor into the ignition coil.
>On your second schematic you use two transistors to discharge the capacitor into the ignition coil.

>Just two different ways to do the same thing or is there a reason that one is preferred over the other due to reliability or something else.

You are quite right, I learned these transistors are not nessary for this saw. I first did thought that the pulse signals are very small in voltage. but this anxiety made me wind it too much, as much as 300, This was too big! Now I know 30 to 40 can be enough for it.


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>You might want to coat all your components in epoxy to protect them from moisture and oil.

Yes you are right. Magnus says just the same to me, to which I agree.


>I do not know of any schematics for ignitions that have limiting coils.    Besides those coils are all incased with epoxy and I doubt that you could get into one to modify it in any way.
>If you could get into one of the newer limiting coils and since these ignition systems are solid state devices there is probably a component in there that could be changed so that the RPM range could be made to go higher. 

Humm, it's our future project!

Many thank.