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 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 availability 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 didd= le > 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 of > 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 for > the > > > ones I've seen. The voltage generated by the magnet is quite small bu= t > > 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 in= to > > the > > > primary you should get a clean output on the secondary at a much high= er > > > 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 finger= s > > > 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 is = a > > >> pretty simple setup. > > >> Best Regards > > >> Luis > > >> On 25 Nov 2012 22:13, wrote: > > >> > > >>> Another possible problem is the primary winding getting wired rever= se > > >>> polarity by someone fiddling with the unit. This will have a seriou= s > > >> 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 connecte= d > 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 more > > >>>> 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 for = 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 to > > >>>> isolate the problem. > > >>>> > > >>>> Magnetos work by interrupting the current in a short-ciruited coil > > (the > > >>>> primary) which induces a much higher voltage in an overwind (the > > >>>> secondary). The switching used to be a mechanical switch, but thes= e > > >>>> days is usually electronic and triggered by measuring some variati= on > > 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 frequenc= y > > >>>> 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 your > > >>>> 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 > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .