Bench Time for a Super Mini SL

[sawnami]

Ran one of my three Super Mini SL's across the bench to see what it would take to get it running. The solid state coil was only firing on the start leg so it was running around 20° retarded from where it normally should be when running. It seemed worthy of a new coil so I took one for a XL-12/SXL and pressed the core out of it and pressed the SuperMini's into it. It runs amazingly vibtation-free.

youtu.be/pUpOTfG2MHw

[jerseyhighlander]

Love that saw.

What ate the old coil? Looks like corrosion or something disagreeable ate into it.

[sawnami]

Nov 24, 2018 14:54:34 GMT -5 jerseyhighlander said:

Love that saw.

What ate the old coil? Looks like corrosion or something disagreeable ate into it.

Thanks!
The blue shell appears to have softened and deteriorated in that area. The resin part is intact.

[undee70ss]

Those blue Prestolite/Wico modules were known to be bad. How hard was it to press out as I don't think they were meant to be pressed out. I suspected the modules were the same, only the core was different. At least thats another option on those series of saws. Thanks for posting that.

[sawnami]

It presses out fairly easy. You just lift the spring clip enough to clear the closed end of the core and push it out.

[onlyhomelites]

Beautiful saw and nice fix! I've played around with the coil swapping a bit myself...as long as you stick with the proper manufacturer, the ignitions seem to be pretty forgiving from one saw to another. One time I even was able to take an electronic coil from a Super 2 and use it on a Super XL with a Phelon flywheel and coil leg!

[sawnami]

Thanks Leon!
I sometimes wonder if it has to do with how the coil windings are wound. I remember that the distributor pole piece for an Oldsmobile wouldn't work on a Chevrolet because the windings were wound opposite of each other.

[5terrysupersaws]

Not an expert in this area (ex GM Tech), but the difference between a Wico and Phelon flywheel is magnet polarity.

The primary cause of failure in a Prestolite module is a poor system ground connection (casual/friction) between
the armature and module.

[undee70ss]

Nov 25, 2018 0:23:29 GMT -5 5terrysupersaws said:

Not an expert in this area (ex GM Tech), but the difference between a Wico and Phelon flywheel is magnet polarity.

The primary cause of failure in a Prestolite module is a poor system ground connection (casual/friction) between
the armature and module.

Is there anyway of preventing that casual/friction?

[sweepleader]

I think what he meant was the connection was casual and made only by friction with the core. If that is correct, more friction would lead to a better connection. Maybe stuffing a shim or short piece of bare wire in between the contact points would help??? Guessing here, never fixed one.

[5terrysupersaws]

Correct sweepleader, the system ground connection is a terminal on the module that makes casual contact with the 
armature when the module is seated against it.

                                                    _________
                                                    |               | 
                                                    |  core       | 
                                                    |               | <---- System Ground 
                                                    |________ |  
                                                      module 

Corrosion in this area can cause a loss of contact, resulting in no spark and can damage the SCR.

Full credit given to dynodave for his explanation in the thread below;

 houseofhomelite.proboards.com/thread/7304/homelite-super-auto-prestolite-coil

[blythkd]

I know this is an old thread but I don't understand something that I read here and I'm trying to learn. First off, I can disassemble and repair almost anything mechanical but, and here's the but, when it comes to electrical, especially electronics, I'm about the biggest dummy you'll ever find. I know when an electronic ignition won't work, replace it. That's about the extent of my knowledge on electronic ignitions.

So earlier in this thread is a reference to "only firing on the start leg." I'm trying to put 2 and 2 together here and wonder if there's a start leg and run leg similar to capacitor terminology? Or am I way off base?

[jerseyhighlander]

Sept 28, 2019 9:01:00 GMT -5 blythkd said:

I know this is an old thread but I don't understand something that I read here and I'm trying to learn. First off, I can disassemble and repair almost anything mechanical but, and here's the but, when it comes to electrical, especially electronics, I'm about the biggest dummy you'll ever find. I know when an electronic ignition won't work, replace it. That's about the extent of my knowledge on electronic ignitions.

So earlier in this thread is a reference to "only firing on the start leg." I'm trying to put 2 and 2 together here and wonder if there's a start leg and run leg similar to capacitor terminology? Or am I way off base?

It's not completely off from start/run capacitors except it doesn't involve a capacitor. The coil itself is essentially a step up transformer (you need to have some understanding of the physics of transformers here) with a primary winding and a secondary/high voltage winding. The flux of the magnets on the flywheel isn't enough to give you the juice you would need straight from the coil to the spark plug, so it uses the magnets to create the current it can in the primary winding, that then creates and even bigger magnetic flux to excite the secondary winding with much higher energy. This with the points/condenser or module being part of the works of the primary winding.