B.T.H Magneto-Generator Series 'A' Comet

Michel

Michel

Well Known and Active Forum User
VOC Member
Hello,
Does anyone has the wiring diagram with the the BTH generator, the cutout and the 7 positions Miller switch ?
It would help me.
Thanks.
 
Michel

Michel

Well Known and Active Forum User
VOC Member
How to say.
There is the upper part in bakelite (or other) with CH D H L write on it and there is the inner mechanism. They are fixed together with two screws and their nuts.
If it is wrong, the mounting can be reversed by 180 °.Do you understand my doubt ?
Would you have some pictures of your switch on all sides?
Thank you for your help.
 
Simon Dinsdale

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
From the riging position, looking at the switch it has OFF CH H L across the top. Inside the headlight shell the resistor is on the timing side / exhaust side of the bike.
Img_1860.jpg
 
Last edited by a moderator:
Simon Dinsdale

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
Meant to add, as you say the switch can be assembled 180° around inside the headlight shell. It works either way, I just assembled mine in that orientation as it appeared easier for the wiring loom.
 
Michel

Michel

Well Known and Active Forum User
VOC Member
Good evening,
(Kind reminder)
Does anyone has the wiring diagram with the the BTH generator, the cutout and the 4 postions and 7 connections Miller switch ?
It would (really) help me.
Thanks.
 
Michel

Michel

Well Known and Active Forum User
VOC Member
vin998 said:
Michel
Just been taking some photos of my bike for you. Is this the BTH mag / dyno you have?
View attachment 14491

If so the original BTH (not Miller) cutout fitted on top of the toolbox. Here is a picture of mine. You can just see the circle in the top that shows the BTH symbol. The cutout can be replaced by a diode rated at 10A to 15A. The original BTH cutouts are extreamly difficult to find and I don't know of any replicas been made. The cutoput just stops the battery discharging back through the dynamo when the dynamo is not generating.
View attachment 14493
The orignal Miller headlight switch has 4 positions. Off, Ch, H, L. When used with the BTH dynamo, Off, disconnects the dynamo from the battery. Ch connects the dynamo to the battery through a resistor to limit the charge rate. H switches the headlight on and bypasses the charge resistor to allow maximum charge. L switches the side light on if fitted. The 3 position switch you have is a aftermarket copy which was never used on Vincent's and so will not work for this charging system as it is. There are replica 4 position switches available, I think the VOC spares sell them, but these only have four contact positions on the back which is what series B & C used. The switch you need has seven contacts on the back to allow for switching the charge resistor. You may have to find an original.
View attachment 14494

There is a possible alternative. Brian Werrett (in UK) has just completed restoring the Model PS for the club and was shown on the front of June's MPH. This bike also has a BTH with the cutout. Brian is thinking of getting an electronic regulator made by a company which will act as the cutout and also regulate the dynamo output so no charge resistor or switch in the Off or charge position will be required. This regulator will automatically work like the later bikes did, but it will only work on this type of BTH mag dynamo. If you send me your email address in a private message through the forum, I will forward it to Brian.
Regards
Simon
VOC Machine Registrar
Click to expand...

Hello Simon,
Do you have better pictures of your BTH cutout withe the BTH circle on the top.
Thank you.
Michel.
 
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