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Old 19th Sep 2018, 7:50 pm   #1
kenb214
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Default Radiomobile 1070 XS

Hi,

Apologies if my post is a bit basic.

I am looking to fit a Radiomobile 1070 XS car radio to my classic car. Car is positive earth and radio has switch to set it to positive earth.

The area of confusion is that there is no earth wire from the radio. There is a power wire and a short 6 inch aerial wire (with female threaded end connection), plus the speaker wires.

I don't intend to use the radio normally, it has an mp3 lead which I will be using instead - so no aerial required on the car.

Do I earth to the radio chassis/casing or is earth only through the aerial?

Thanks in advance,

Ken
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Old 19th Sep 2018, 8:47 pm   #2
Goldieoldie
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Default Re: Radiomobile 1070 XS

Hi
Just connect a wire from the metal case on the radio to the metal of the car
The power lead needs an inline fuse ,about 1 to 3 amp will be fine
Connect this lead to a power source such as the switched on from the ign switch
Cheers
Pete
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Old 19th Sep 2018, 9:07 pm   #3
kenb214
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Default Re: Radiomobile 1070 XS

Hi Pete,

Thanks for the answer.

There are one or two threaded holes in casing, would it be ok to use a crimp ring connector held on with a screw into tapped hole or better to solder to casing?

Regards,

Ken
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Old 19th Sep 2018, 10:35 pm   #4
'LIVEWIRE?'
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Default Re: Radiomobile 1070 XS

IIRC, the metal case of Radiomobile Radios of that era (late 1960s to mid 1970s) is (a) quite a heavy gauge) and (b) not steel, so almost impossible to solder . It will be perfectly OK to use a crimp ring connector screwed to one of the threaded holes to attach an earth lead. These holes, plus one in the bottom cover, were provided to allow the attachment of mounting brackets, but I don't recall what thread they are -unlikely to be metric, since, believe it or not, all Radiomobile Radios in those days were designed and built in Britain.
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Old 19th Sep 2018, 11:56 pm   #5
Goldieoldie
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Default Re: Radiomobile 1070 XS

As previous post ,screw into the case is fine .Be careful it's not too long as you do not want touch something inside !
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Old 20th Sep 2018, 4:55 am   #6
TonyDuell
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Default Re: Radiomobile 1070 XS

I am a little concerned about that 'MP3 lead' which I assume is an audio input.

The screen of that lead is most likely connected to one of the power rails of the radio. If it's the negative rail then the screen would be at the same voltage as the car body in a negative-earth car (the common one) but will be at -12V (battery 'live') in a positive earth car. So if it touches the car body, or if it is connected to an MP3 player that is also powered from the car battery the result could be a short circuit. If you're lucky that will blow the fuse. If not it could do some more serious damage.

I think it will be fine if you are playing from a device that runs off internal batteries (and is not being charged from the car battery!) and if you keep said device out of electrical contact with other parts of the car.
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Old 20th Sep 2018, 8:54 am   #7
'LIVEWIRE?'
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Default Re: Radiomobile 1070 XS

Good point, Tony. I can't place the 1070XS in the Radiomobile range, but, as it's a variation of the 1070/1080/1085, etc. series, the return (screen) side of the audio circuit is connected to the a.f. Positive line regardless of the polarity of either the radio or the vehicle. Because of this it is important that, if any external device is either powered from, or charged via, the vehicle's battery, any metal parts, including the screen & plug(s) of the audio cable connecting the MP3 player to the radio, are isolated from both the radio casing and the vehicle metalwork. I included notes to that effect in one of my posts in the 'sticky' thread about 'Adding Aux-in connectors to car radios'.
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Old 20th Sep 2018, 9:48 am   #8
kenb214
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Default Re: Radiomobile 1070 XS

Hi,

Thank you all for your advice.

I'll make sure the connector is isolated when not in use and the mp3 player will not be charging via the car so that should also be fine.

Thanks again, much appreciated.

Regards,

Ken
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