Solid state ignition

[Al Smith]

As most of use know,about every internal combustion engine,made in the last 20 or so years,has a solid state ignition.A thought occured to me,at o-dark-thirty,as I was on my way to work,as to the causes for these to fail.This is only a possibility,but I think it may have some merit.Chainsaws,as we know,are made of aluminum.Aluminum,by it's nature,is a good conductor of both electrical energy,and also heat,or thermal energy,due to the abundance of free elecrons in it's outer,or valence shell of the atom.Aluminum ,is also prone to oxidixation,if exposed to the elements,and forms aluminum oxide,which is an insulator.Another phenominum occures when dis-simular metals are in contact with one another.This is called electrolosis ,or galvanic action,and simpley put the 2 metals act like a tiny battery,and pass teeny amounts of current,between them,which could lead to a plating,or anodization of the metal parts.In the case of a saw engine,we have the module,with it's soft iron lamenations,attatched the the aluminum of the saw. Due to factors such as expansion and contraction,possibley electrolsis,and vibration,it would,in my opinion,be possible to compromise the intgrety of module to the saw,with regards to elecrtical continuity and heat transfer.If in my opinion,the module could not transfer the heat to the block,and thus be dissipated by the air blast,you would ultimately "cook" the elecrtonic trigger circuits in the module.By the same token,if a high impedence grond condition occuerd you cpuld possibley get a transiate voltage spike,and "fry" it electically.In electronic circuits,involving "heat Sinks" a conductive paste is applied between the component and the heat sink.This insures both a good electrcal connection as well as a good thermal transfer.AS a thought for possible prevenative maintanence,as well as new intallation,perhaps cleaning the junction point with a "Scotchbrite" type pad,and useing heat compound,could prove benificial.This theory may have been discussed in the past,and I'm not aware of it.If anyone out ther in chainsaw land has any thoughts of the matter,please speak up.Sometimes the replacement ignitions,cost more than the saw is worth

 

[scottr]

Thermal Junction Compound

Al , the thermal junction compound is a good idea but remember the capacitor and the scr that dumps the capacitor charge will need to be physically mounted to metal for any cooling effects. I'm not sure if the are . I have a breakerless ignition that will not work when cool , if it would fail I would cut it open to see how the capacitor and scr are mounted . Maybe someone out there has taken one apart . My guess is that the capacitor fails first . The thermal junction compound on the aluminum to iron coil laminations to help keep them cooler is a good idea .

 

[stihltech]

ground

That is one of the steps when diagnosong an electronic ignition. Check all mounting for corrosion and bad grounds. As far as the paste goes, probably wouldn't hurt. The failure rate has went way down compared to 15 years ago.

 

[NevadaWalrus]

I do believe heat is the number one cause of failure but from debris accumulation blocking air flow from the coil and cooling fins. Some saws are worse about this then others but too many people fail to ever clean behind the cover.

 

[Saw Man]

Heat, and bad connections were the major culprits, along with one other that is rarely talked about.

Operator-test person fault.

A check for whatever reason is done, with the sparkle plug removed, and laid on some metal part. Starter cord is pulled alot....because there's no compression...so it's easy to just pump the starter.

Flywheel magnets are whipping past the coil legs building an magnetic field, which is converted into electricity. Now there is only some rects & caps can take before current blowouts (leaks).

Caused by poor-bad-intermittent contact with the sparkle plug, and the saw...usually the cylinder. If the current can't complete a circuit...it blows rects & caps.

 

[Tony Snyder]

Whats new? All known stuff. But I guess it don't hurt to air it again.

 

[heviarti]

while we're on the subject.. where are the atom modules?

 

[dbabcock]

You forgot to mention the influence of the Higgs Boson.