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Author Topic: BTH Regulator  (Read 3597 times)

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Offline A31ndrew

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BTH Regulator
« on: 15 Dec 2014 at 08:07 »
Hi - I'm looking for a BTH regulator for a 1931 model A31. Can anyone help, please.
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Offline podge

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Re: BTH Regulator
« Reply #1 on: 15 Dec 2014 at 11:40 »
Hi Andrew

I had the same problem with my A32 when I rebuilt it 7b years ago. The BTH cutouts are like hen's teeth - you can't find them. So I made a cutout using a diode and added a 6.8 volt zener diode to hold the voltage to the battery down to 6.8 volts. The charging current is 1/2 amps. It has worked fine for 7 years. When you switch on the headlights the charging current comes up and backs off the discharge. I mounted the diode and a fuse in a small diecast box that I got from Maplins which is almost identical in size to the original BTH cutout. The zener diode I mounted on an adjcent aluminium bracket. I found that I needed to fit a cutoff switch to the battery to stop any long term leakage through the reverse resistance of the cut out diode. I attach a sketch of the wiring, The cutout diode came from Maplins and the zener diode fror Mouser Electronics in the US. Hope this helps.

Regards

Paul
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Offline A31ndrew

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Re: BTH Regulator
« Reply #2 on: 16 Dec 2014 at 04:02 »
Hi Paul,
Thanks for the reply - looks like a good Plan B in the event that the original part does not turn up. You're right about them being like hen's teeth - I didn't even know they existed until I discovered I hadn't got one .....
Andrew
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