MGB Register Forum

Vic Butler wrote:
> It's possible that green is the power but I can't be sure. What happens if
> you connect one wire to negative and the other to positive and then try
> reversing them?

That was the first thing I tried .. with nothing moving .. even reversed .. hence the casing needed to be in the equation

I can't check the wiring on mine because the aerial is
> behind the splash panel which has had copious amounts of waxoyl plastered
> over it and at the radio end it's connected to the radio housing. It's a
> removable radio.

No worries .. I had to chisel mine out of a load of mastic/ resin !

What intrigues me is .. if the motor only rotates one way (ie simple DC), how does the winder change direction ?

Cheers

D

So the 2 wires on that basis are both power. Maybe one is for operation by the radio and the other to a live fused supply. I can't remember how I wired mine it was so long ago.
What happens if you earth the case to negative and connect both wires to positive?
I don't know how the aerial retracts when the power is cut. I know the motor on my aerial is running because I can hear it when the aerial retracts.
What do you mean by points rotator?

Vic Butler wrote:
> So the 2 wires on that basis are both power. Maybe one is for operation by
> the radio and the other to a live fused supply.

Agreed

I can't remember how I
> wired mine it was so long ago.
> What happens if you earth the case to negative and connect both wires to
> positive?

It retracts and continues to try to

> I don't know how the aerial retracts when the power is cut. I know the
> motor on my aerial is running because I can hear it when the aerial
> retracts.

On mine, both extension and retraction are powered by the motor .. there is a clever duel points system on the inside which open and close along with the winder.

I took the motor out, which has a screw on a shaft that moves the winder .. it seems to switch rotation / winding which is why I thought the polarity was crucial ??

I think I will sleep on it and reassess tomorrow

Cheers

D G

That asterix should be 'screw' ... p.c. monitor ???

Ok .. it should be an 'Archimedesscrew'

Presumably the aerial was working on the car at one time. I wonder if the switch isn't reversing the motor.
The switch obviously cuts off the motor when the aerial is fully extended and again when fully retracted. When the radio is switched off the power is from the other supply which reverses the switch allowing the motor to run backwards.

Further to my previous posting, I think that both the green and blue wires are power supplies and therefore are positive. The case is earthed via the car body and one wire is the power to extend the aerial and the other to retract.
That's my theory for what it's worth.
What happens if you earth the case to negative and connect one wire to positive? If it tries to continue to retract what happens if the other wire is connected? This is getting more and more intriguing and being curious I'd like to know the answer.

With the case live the blue is constantly connected to negative Then the green extends it when connected to negative and it retracts when the green is disconnected

Sounds like it's positive earth only. Very odd as it's fitted to a negative earth car where the positive is the live side.

Fixed it 😊

I was not going to give up just yet so tried rotating the cylinder containing the magnet over the coil by 180 degrees 🤷🏼‍♂️

To my delight it worked 👍

Not sure about the physics though 🤔

Thanks for sticking with me Vic

Cheers

Dave G