Vintage Car Stereo Wiring Help
Discussion
I'm sure someone on here will have a memory for this stuff...or know how to safely work out which is which.
Background....I'm restoring an MGB. I want to keep the old radio/cassette player in place, and add a small bluetooth amp behind the dash somewhere.
The new bluetooth bit is all easy. I was planning on building a switchover box using a couple of DPDT relays in to switch the speakers from the old radio to the new amp. All good so far.
The trouble I'm having is identifying the wires on the old radio (it's a Sanyo if that helps)
Only 4. There's a socket for the ariel lead separately, and the thick earth wire is just connected to the case.
So, presumably if there's power and earth, that meant that the speakers must have been earthed to the chassis? Is that right? And does that mean that my cunning plan won't work at all?
I'm also not sure which leads were which, or how to safely test. From the tags I left on the harness when I cut it 5 years ago, I *think* that the speakers were probably the white and yellow, which would make blue the power.
Any advice gratefully received!
Background....I'm restoring an MGB. I want to keep the old radio/cassette player in place, and add a small bluetooth amp behind the dash somewhere.
The new bluetooth bit is all easy. I was planning on building a switchover box using a couple of DPDT relays in to switch the speakers from the old radio to the new amp. All good so far.
The trouble I'm having is identifying the wires on the old radio (it's a Sanyo if that helps)
Only 4. There's a socket for the ariel lead separately, and the thick earth wire is just connected to the case.
So, presumably if there's power and earth, that meant that the speakers must have been earthed to the chassis? Is that right? And does that mean that my cunning plan won't work at all?
I'm also not sure which leads were which, or how to safely test. From the tags I left on the harness when I cut it 5 years ago, I *think* that the speakers were probably the white and yellow, which would make blue the power.
Any advice gratefully received!
CrutyRammers said:
Thanks. So they do earth to the chassis then. Is that likely to be a bad thing for modern speakers or don't they care?
If they are standard passive speakers, it doesn't matter.But you should be running both the "plus" speaker wire and a "ground" (-) wire to the speakers - don't just ground one side of the speakers to the chassis.
See link :
https://www.manualslib.com/manual/1079968/Sanyo-Ft....
I guess this is where the picture above has come from.
But yes, it looks like for yours that the yellow is likely to be the right speaker +, with the right speaker - being fed straight to the nearest ground on the car chassis. White is probably the left speaker +.
The question then is which of the other wires is 12v+ and ground? Asuming black is ground (as in the diagram) that would leave blue as 12v+.
Or it could be the white?
Are the white and blue wires the same gauge? The heaviwe guage will be for the power, lighter for the speakers.
Oh for the days when car audio was this simple (and crap! )
https://www.manualslib.com/manual/1079968/Sanyo-Ft....
I guess this is where the picture above has come from.
But yes, it looks like for yours that the yellow is likely to be the right speaker +, with the right speaker - being fed straight to the nearest ground on the car chassis. White is probably the left speaker +.
The question then is which of the other wires is 12v+ and ground?
Asuming black is ground (as in the diagram) that would leave blue as 12v+.Or it could be the white?
Are the white and blue wires the same gauge? The heaviwe guage will be for the power, lighter for the speakers.
Oh for the days when car audio was this simple (and crap!
)Edited by Piersman2 on Monday 2nd March 18:46
TonyRPH said:
If they are standard passive speakers, it doesn't matter.
But you should be running both the "plus" speaker wire and a "ground" (-) wire to the speakers - don't just ground one side of the speakers to the chassis.
This. I would have expected the unit to earth through the chassis mounting with the black wire as the common return for the speakers.But you should be running both the "plus" speaker wire and a "ground" (-) wire to the speakers - don't just ground one side of the speakers to the chassis.
BTW I assume the MGB has got a negative earth return? A lot of BMC stuff of that period had a positive earth, though as on my Sprite they weren't too difficult to convert to the now normal negative earth. I've forgotten why manufacturers did this, something to do with corrosion at the battery terminals (?) but it started prewar and continued well into the Fifties.
OK this is starting to make sense.
The blue wire is slightly heavier than the black, white and yellow. I'd also taped the black, white, yellow together.
So that would suggest:
Blue: power in
White/yellow: speaker +
small black: speaker - (for both speakers)
...With the big heavy black wire from the case earthed to the chassis.
So I'll have to do some slightly different routing in my switchover box for each source but nothing difficult.
Yes it is a -ve earth BTW, I think some of the early MGBs were +ve but mine is quite a late one.
Thanks everyone for your help
The blue wire is slightly heavier than the black, white and yellow. I'd also taped the black, white, yellow together.
So that would suggest:
Blue: power in
White/yellow: speaker +
small black: speaker - (for both speakers)
...With the big heavy black wire from the case earthed to the chassis.
So I'll have to do some slightly different routing in my switchover box for each source but nothing difficult.
Yes it is a -ve earth BTW, I think some of the early MGBs were +ve but mine is quite a late one.
Thanks everyone for your help
A simple way to verify the power lead is to connect a multimeter on the ohms range between radio chassis and the wire you think is positive.
Turn the radio on and off and when on, you should get a reading (value irrelevant) and when off it should be open circuit.
I used to repair these very radios (I worked for a Sanyo repair agent) but that was some 40 years ago!!
Turn the radio on and off and when on, you should get a reading (value irrelevant) and when off it should be open circuit.
I used to repair these very radios (I worked for a Sanyo repair agent) but that was some 40 years ago!!
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