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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22447 Location: UK
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MVPeters
Joined: 28 Aug 2008 Posts: 822 Location: Northern MA, USA
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Posted: Sat Nov 12, 2011 11:30 pm Post subject: |
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I don't think it matters, Rick. The condenser is dealing with HT coil voltage rather than LT 6V or 12V, isn't it?
If you've got a 'sports' or 'high-output' coil you might need someting different; but again, I don't think so. _________________ Mike - MVPeters at comcast.net
2002 MINI Cooper 'S' |
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Salopian
Joined: 05 Jan 2010 Posts: 354 Location: Newport Shropshire
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Posted: Sun Nov 13, 2011 1:09 am Post subject: |
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The condensor is across the points so nominally sees the LT voltage. Provided any voltage is not over its safe limit the only other relevant matter is its capacity and this is pretty standard for points systems. I've used mini ones for all sorts including one 6v car with no problems.
This is a simplification but get on and try it Rick! _________________ Jonathan Butler
Alvis SD 12/50 1928 MG TD 1950 |
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MVPeters
Joined: 28 Aug 2008 Posts: 822 Location: Northern MA, USA
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Posted: Sun Nov 13, 2011 2:18 am Post subject: |
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So there you have it! Whether it's low or high tension voltage, at least we agree it probably doesn't matter!
(I think Salopian is correct, by the way).
Although it doesn't directly deal with this particular question, there's a good article on ignition systems here:
http://www.mgb-stuff.org.uk/ignitiontext.htm _________________ Mike - MVPeters at comcast.net
2002 MINI Cooper 'S' |
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peter scott
Joined: 18 Dec 2007 Posts: 7118 Location: Edinburgh
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Posted: Sun Nov 13, 2011 11:45 pm Post subject: |
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Although the points are switching the LT side, when they open the back EMF generated by the coil does generate a very high voltage (hence the sparking) so yes, the condensor does have to tolerate HT.
As already stated, a condensor used in 12 volt systems will work fine in a 6 volt set up.
Peter _________________ http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Mon Nov 14, 2011 4:50 pm Post subject: |
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peter scott wrote: | Although the points are switching the LT side, when they open the back EMF generated by the coil does generate a very high voltage (hence the sparking) so yes, the condensor does have to tolerate HT.
As already stated, a condensor used in 12 volt systems will work fine in a 6 volt set up.
Peter |
You hit it on the head Peter. The back emf is about 200 volts, which is why a condenser is required.
If anyone tries to seperate the points with their fingers and ignition on, they will quickly find out .
I wonder how many people are stranded at the roadside with a dud condenser because the "fantastic spark at the points" indicates everything is "OK"?
By the way, if people only bothered to work out the the speed with which points work, they would pay a lot more attention to them.
If you take a maximum engine speed of 6000rpm (because the maths is easier) then they open and close 50 times a SECOND on a four stroke 6 cylinder engine!
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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Salopian
Joined: 05 Jan 2010 Posts: 354 Location: Newport Shropshire
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Posted: Tue Nov 15, 2011 10:20 pm Post subject: |
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Why I said nominally !!!! Didn't want to confuse the issue by bringing in the back EMF (or voltage near enough).
Not sure 200v is really HT but suppose it is against 12 or 6 volts. Jim is spot on of course. _________________ Jonathan Butler
Alvis SD 12/50 1928 MG TD 1950 |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire
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Posted: Wed Nov 16, 2011 9:22 am Post subject: |
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In my tool box I have a 0.2uF (polypropolene metal foil, no less !!) capacitor (its rated at about 1200v) with some fly leads and crocodile clips, if a condenser fault is suspected, quickly connecting this to the CB terminal on the coil and earth will often prove the fault, this is because condensers when they fail tend to fail open circuit, by connecting the external capacitor this way puts it in parallel with the original condenser, effectively substituting it with out any dismantling.
Cost about £1.50 with the clips
Dave
PS capacitors used to be called condensers, its only the automotive industry that still refers to them as condensers. |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Wed Nov 16, 2011 1:09 pm Post subject: |
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Many years ago, I remember the fragility of condensers being demonstrated.
An old, but good one was tested satisfactorily and it was the subjected to slight knock by tapping it on the bench. It then tested faulty.
The type typically used in ignition systems is only a strip of aluminium foil rolled up with an insulating strip between the turns.
The moral seems to be - treat them gently, store them carefully and reject any chucked down on the counter by a store-keeper at the point of sale
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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JohnDale
Joined: 19 Mar 2008 Posts: 790 Location: Kelvin Valley,Scotland
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Posted: Wed Dec 28, 2011 12:09 pm Post subject: |
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Another good reason for fitting the simple type of electronic ignition - does away with points & condenser. Have done that with all my cars..... but still carry the points etc in the boot - belt, braces,....& a piece of string!
All the best, JD. _________________ 1958 Ford Zephyr Mk2 Convertible
1976 Ford Granada Ghia. |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Wed Dec 28, 2011 12:45 pm Post subject: |
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I too carry spare points and condenser and rotor arm. But I have not converted to electronic ignition because I can easily diagnose a fault with non-electronic ignition systems at the roadside with nothing more than a piece of wire by "splash" testing for continuity or not.
I would not know where to start with electronic systems (particularly conversions), which I know from past experience can and do fail.
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire
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Posted: Thu Dec 29, 2011 11:39 am Post subject: |
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I have used this £10 electronic ignition kit http://www.maplin.co.uk/ignition-amplifier-kit-3162 on a number of vehicles, it retains the points and the condenser can be left in place, although its not doing anything.
Its basically the same as the transistor assisted ignition systems that manufacturers began to fit in the late 70's; retaining the points as a trigger, but the actual switching of current to the coil is electronic; this delivers a much cleaner "break", resulting in both a quicker field collapse in the coil when the points open and more efficient coil "charge" when the points close, with no dependancy on the condenser!
A useful feature is that if it fails, a flick of a switch takes you straight back to conventional ignition.
Dave |
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Jim.Walker
Joined: 27 Dec 2008 Posts: 1229 Location: Chesterfield
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Posted: Thu Dec 29, 2011 2:22 pm Post subject: |
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Interesting Dave.
Just a question, to which I suspect I know the answer. Does it only work on 12 volts?
Jim. _________________ Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then! |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4105 Location: South Cheshire
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Posted: Thu Dec 29, 2011 7:26 pm Post subject: |
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Jim.Walker wrote: | Interesting Dave.
Just a question, to which I suspect I know the answer. Does it only work on 12 volts?
Jim. |
Hi Jim
The kit is designed and sold as a 12v kit, but the maker (Vellaman) does advise the components to change for 6v use; its a couple of resistors that cost about 50p!
The kit is only for -ve earth, I did alter one for a 6v +ve earth car, but you end up hardly using any of the components; just the design! still at £20 its still not expensive
Dave |
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