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6V Zener

Submitted by cliff_curtis on Tue, 22/08/2023
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Electrical

The final half mile of my road in Bulgaria is very bumpy being made up from railway sleepers.

My Dominator is therefore tested every journey including the electrics.

The law states that the headlights must be on at all times.

A momentary break in the battery connection, I suspect the old switch, routes the alternator current straight to the light bulbs, pop. This was overcome on 12V models with a 15V Zener diode but is there a 7.5V Watt plus diode available to fit on my Norton to stop this problem. 

I have looked on the internet, a 1N3306BR fits the bill but I've failed to find a supplier who will sell less than 100 at a time. 

Has anyone else solved this?

 

 

Submitted by ian_soady on Tue, 22/08/2023

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.. I've ever seen a 6V Zener. I was looking for one a couple of years ago when I was rebuilding a Francis Barnett and wanted toupgrade the elctrics but like you drew a blank.

You may be better advised to convert to 12 volts although even those Zeners are becoming rare.

Submitted by alan_osborn on Tue, 22/08/2023

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Lucas stopped making Zeners in the 1980s, we have been coasting ever since. Saying that there are 100s of them still being used very sucesfully ie if it ain't broke don't fix it! But saying that the 12V Zener does tend to drift up in voltage. I can check it if you have doubt or fit a monitor either a Chinese digital display or my coloured LED display or trust your luck.

Back to original problem.There never has been a 6V (7.5V) zener as per the 12V Lucas item. The one mentioned above is only 50W so on an 80W or even more alternator, you are sailling close to the wind. There is an answer. I sell a 6v regualtor rectifier, this will do the job. But again looking at the original problem why have loose wires/connections?? Fix this problem.

Submitted by tony_ripley on Tue, 22/08/2023

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Hi Cliff,

Just get yourself the A Reg 6, this will solve your problems, but still try to fix the loose wire!

http://www.aoservices.co.uk/a_reg.htm

Submitted by cliff_curtis on Wed, 13/09/2023

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I have fitted LED headlamp and tail lamp bulbs and have now compounded the problem as the alternator is trying to overcharge the battery with the lights on BUT, problem partly solved. I have removed the wire from pin 7 on the headlamp switch. This disconnects the second alternator winding that normally comes into play only when the headlamp is on. The amp-meter still shows a low charge with the headlamp on which is great. Now with less"juice" available the possibility of overvoltage occurring in the event of a battery disconnect is reduced. It also means that if I fit a 50W zener, this should be sufficient as I assume the single alternator winding is rated at 40W. As I am experiencing problems at low speed coming home on a very bumpy road I hope I'm going to be ok now. 

Submitted by alan_osborn on Thu, 21/09/2023

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The original problem was a momentary break in wiring causing battery loading to disappear, surely you have found and cured this problem? Also LEDs are more easly blown with high voltage than traditional tungstan lamps.

Looking back at the idea of a 7.5V zener, if that were to lose its battery load would also fail.

On the 6V bike the battery is considered a major part of the load and regulation. If the wiring to the battery is not intermittant then perhaps the battery itself is. This is also a case for having as large a battery 'flooded lead acid' as you can fit.

 


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