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Condenser 6v vs 12v
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Rick
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Joined: 27 Apr 2005
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Location: UK

PostPosted: Sat Nov 12, 2011 8:55 pm    Post subject: Condenser 6v vs 12v Reply with quote

On a 6v system, can I use any condenser (6v/12v) or does it need to have been designed specifically for a 6v system?

Does the physical size of the condenser make any difference, apart from obviously impacting whether it'll physically fit Smile ?

I've a feeling this has come up before, but in looking at previous condenser threads I've not spotted it

thanks, R
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MVPeters



Joined: 28 Aug 2008
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PostPosted: Sat Nov 12, 2011 11:30 pm    Post subject: Reply with quote

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.
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Salopian



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PostPosted: Sun Nov 13, 2011 1:09 am    Post subject: Reply with quote

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!
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MVPeters



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PostPosted: Sun Nov 13, 2011 2:18 am    Post subject: Reply with quote

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
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peter scott



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PostPosted: Sun Nov 13, 2011 11:45 pm    Post subject: Reply with quote

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
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Jim.Walker



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PostPosted: Mon Nov 14, 2011 4:50 pm    Post subject: Reply with quote

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 Shocked .
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"? Rolling Eyes

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.
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Salopian



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PostPosted: Tue Nov 15, 2011 10:20 pm    Post subject: Reply with quote

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.
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ukdave2002



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PostPosted: Wed Nov 16, 2011 9:22 am    Post subject: Reply with quote

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 Very Happy

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



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PostPosted: Wed Nov 16, 2011 1:09 pm    Post subject: Reply with quote

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.
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JohnDale



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PostPosted: Wed Dec 28, 2011 12:09 pm    Post subject: Reply with quote

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.
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Jim.Walker



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PostPosted: Wed Dec 28, 2011 12:45 pm    Post subject: Reply with quote

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.
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ukdave2002



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PostPosted: Thu Dec 29, 2011 11:39 am    Post subject: Reply with quote

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



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PostPosted: Thu Dec 29, 2011 2:22 pm    Post subject: Reply with quote

Interesting Dave.
Just a question, to which I suspect I know the answer. Does it only work on 12 volts?
Jim.
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ukdave2002



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PostPosted: Thu Dec 29, 2011 7:26 pm    Post subject: Reply with quote

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 Very Happy

Dave
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