Hi Richard, I did supply Luis with the correct manual from the manufacturer...most have a at least a multimeter, which would be adequate for most of the tests if one knows what the test parameters are. One can read the manual, or embark upon one's own diagnostic approach. Either way I sincerely wish Luis luck with his chainsaw. I just thought the manufacturers service info might be helpful Regards On Mon, Nov 26, 2012 at 8:19 AM, Richard Prosser wrote= : > It is a rather more effective approach than hunches and guesswork as to > what the fault might be. > One might quickly stumble upon the solution that way, one might also didd= le > about without effect > > Or one can carry out a series of tests to arrive at a diagnosis - > especially if the service manual etc. is not available and the availabili= ty > of "proper" test tools is unknown.. > > RP > > > On 26 November 2012 13:49, Perry Curling-Hope wrote: > > > Richard, That is correct. ((in the region of 200 milliohms) > > > > The Shindaiwa service manual defines the correct resistance of the > > primary...0.3 to 0.4 ohms. > > That's not an opinion...that's what the manufacturer specifies. > > > > The manual also outlines in detail step by step how an owner of the > > machine, with non specialized tools (a multimeter and an automotive > > ignition analyzer) may proceed with all the possible tests which will > > establish if the modules are serviceable or require replacement. > > > > It is a rather more effective approach than hunches and guesswork as to > > what the fault might be. > > One might quickly stumble upon the solution that way, one might also > diddle > > about without effect > > > > > > > > > > > > > > On Mon, Nov 26, 2012 at 1:46 AM, Isaac Marino Bavaresco < > > isaacbavaresco@yahoo.com.br> wrote: > > > > > I think that using sinusoidal AC may not produce a too high output > > > because the derivative of the sine is a co-sine, that has a maximum o= f > > 1.0. > > > A very steep current impulse is what is needed to produce very high > > > voltages. > > > > > > Isaac > > > > > > > > > Em 25/11/2012 21:31, Richard Prosser escreveu: > > > > Hi Luis, > > > > > > > > 200 ohms seems very high. 200milli Ohms might be nearer the mark fo= r > > the > > > > ones I've seen. The voltage generated by the magnet is quite small > but > > > you > > > > really want a high current as it's the di/dt that generates the > volts. > > So > > > > the resistance is low. If you can inject a (very) few volts of AC > into > > > the > > > > primary you should get a clean output on the secondary at a much > higher > > > > voltage. Try running a 5V AC supply though the primary in series > with a > > > > resistor or lamp and see what open circuit voltage you get on the > > > secondary > > > > with a scope or even an AC voltmeter. Watch where you put your > fingers > > > > though! > > > > > > > > RP > > > > > > > > > > > > On 26 November 2012 12:15, Luis Moreira < > > luis.moreira1575@googlemail.com > > > >wrote: > > > > > > > >> Hi Alan, > > > >> The wiring seems correct looking at the colours of the wires, it i= s > a > > > >> pretty simple setup. > > > >> Best Regards > > > >> Luis > > > >> On 25 Nov 2012 22:13, wrote: > > > >> > > > >>> Another possible problem is the primary winding getting wired > reverse > > > >>> polarity by someone fiddling with the unit. This will have a > serious > > > >> effect > > > >>> on the intensity of the spark, as well as possibly upsetting the > > > timing. > > > >> If > > > >>> you have a manual for it check which wire colour should be > connected > > to > > > >>> where. > > > >>> > > > >>> > > > >>>> Hi Luis, > > > >>>> > > > >>>> The primary is likely to be quite low resistance anyway and > > therefore > > > >>>> may be OK after all. If both ends of the winding are available, > > check > > > >>>> it hasn't got a short to or earth/frame etc. This is somewhat mo= re > > > >>>> likely than shorted turns, although this is possible. > > > >>>> > > > >>>> Is their a mechanical switch, or is the operation electronic? If > > > >>>> electronic, it can be possible to switch the electronic parts fo= r > a > > > >>>> generic switch unit. It's just a matter of finding something > > suitable > > > - > > > >>>> ---. > > > >>>> > > > >>>> Capacitor failure is also not unknown and the problem is that it > > > breaks > > > >>>> down under high voltage so looks OK when tested. Replacement is > > > >>>> generally the best test for them. > > > >>>> > > > >>>> If you can borrow parts from a similar unit you should be able t= o > > > >>>> isolate the problem. > > > >>>> > > > >>>> Magnetos work by interrupting the current in a short-ciruited co= il > > > (the > > > >>>> primary) which induces a much higher voltage in an overwind (th= e > > > >>>> secondary). The switching used to be a mechanical switch, but > these > > > >>>> days is usually electronic and triggered by measuring some > variation > > > in > > > >>>> the coil current as the magnet passes. Or by separate sensor in > > some > > > >>>> cases. > > > >>>> The capacitor provides a bit of control over the resonant > frequency > > > >>>> which effects maximum voltage and spark duration. > > > >>>> > > > >>>> RP > > > >>>> > > > >>>> > > > >>>> > > > >>>> > > > >>>> > > > >>>> On 26 November 2012 09:49, Luis Moreira > > > >>>> wrote: > > > >>>> > > > >>>>> parts: ignition coil, > > > >>>>> some sort of pickup and the magneto/cap part that > > > >>>>> > > > >>>> -- > > > >>>> http://www.piclist.com PIC/SX FAQ & list archive View/change you= r > > > >>>> membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > >>> -- > > > >>> Scanned by iCritical. > > > >>> > > > >>> -- > > > >>> http://www.piclist.com PIC/SX FAQ & list archive > > > >>> View/change your membership options at > > > >>> http://mailman.mit.edu/mailman/listinfo/piclist > > > >>> > > > >> -- > > > >> http://www.piclist.com PIC/SX FAQ & list archive > > > >> View/change your membership options at > > > >> http://mailman.mit.edu/mailman/listinfo/piclist > > > >> > > > > > > -- > > > http://www.piclist.com PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > > > > > -- > > Perry Curling-Hope > > > > Research and Development > > -- > > http://www.piclist.com PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- Perry Curling-Hope Research and Development -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .