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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 3rd Nov 2009, 11:43 am   #1
luxobarge
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Default Car 8 track advice!

Hello

i wonder if anyone can help.

I purchased a negative earth car 8 track unit (entitled "Mustang") with some cartridges recently and now want to use it in my garage instead, not in the car, so i want to wire it up from a 12v transformer.

The unit was without a connecting jack, just having what looks like an a-typical female 4 pin din plug. A-typical because it looks a bit bigger than normal even though the diamond shape plate is similar to the usual ones.

Maplin were unable to supply the matching male din plug so i thought i woudl replace the the exisitng one to the current easily available type.

removing the cover on the unit revelealed four pins connected as follows clockwise as viewed from rear:

12 o'clock - a black wire (thin gauge) and a yellow wire (thinner gauge - seems to go to unit power light)
3 o'clock -a green wire (thicker gauge)
6 o'clock - a grey wire (thicker gauge)
9 o'clock - red wire (thin gauge), and between this and the 12o'clock wire there is a small capacitor

Questions:

does the unit need a separate amp to work?

if this is really a negative earth unit, is it right that the unit power light is connected to the black 12 o'clock wire?

which are the feed and return wires?

Perhaps the unit is to earth through its casing, in which case what are the functions of each wire?

assuming its a stereo unit, do the speakers also have their return via the common earth?

if i change the din plug, should i go for a 4 pin and replicate the existing, or go for a 6 pin ie to give me a pin for each of feed, return, left speaker out, left speaker return, right speaker out and right speaker return?


all help gretfully received!

thanks

RDS
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Old 3rd Nov 2009, 11:58 am   #2
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Default Re: Car 8 track advice!

You cannot power this unit from a transformer. Transformers supply Alternating Current (AC), but the unit will require Direct Current (DC). In addition to the transformer you will require a rectifier to convert AC to DC and a smoothing capacitor to remove hum from the rectified DC. A 12V (13.8V) supply as used for powering CB radios would be a suitable supply for the unit.
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Old 3rd Nov 2009, 12:02 pm   #3
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Default Re: Car 8 track advice!

In my experience the metal chassis is common return for the speakers and negative for the DC input. Grey and green, as I recall, are the colours often used for speaker left and right lines. Red for 12v, but trace it back to double check.
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Old 3rd Nov 2009, 12:05 pm   #4
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Default Re: Car 8 track advice!

I would recommend a regulated or stabilised 12v DC supply rated at about 2A or so. Maplin will have something suitable. If you use a CB supply, make sure you fuse it at about 2A as they can produce serious amounts of current if you have a short circuit somewhere.

You can sometimes tell whether it's -ve or +ve earth by looking for a biggish electrolytic capacitor inside. If its negative connection is connected to the chassis, then it's -ve earth and vice versa. I must say that "Mustang" sounds a bit American to me (but I know nothing about cars!) and they favoured +ve earth there, so do double check.

When you first power it up, it might be worth doing so with a car indicator bulb in series, so that if something goes horribly wrong, the bulb will absorb the current and light, rather than a cloud of smoke being emitted.

Could you post a picture of the unit, inside and out? This should enable us to tell whether it's got an inbuilt power amp or not.

N.
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Old 3rd Nov 2009, 12:05 pm   #5
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Default Re: Car 8 track advice!

Quote:
Originally Posted by Station X View Post
You cannot power this unit from a transformer. Transformers supply Alternating Current (AC), but the unit will require Direct Current (DC). In addition to the transformer you will require a rectifier to convert AC to DC and a smoothing capacitor to remove hum from the rectified DC. A 12V supply as used for powering CB radios would be a suitable supply for the unit.
Thanks, but i thought the transformers in common use would convert ac to dc and to a voltage selected by a dial? I power my battery piano keyboards from the mains that way, you see.

RDS
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Old 3rd Nov 2009, 12:08 pm   #6
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Default Re: Car 8 track advice!

In that case what you have is a power supply incorporating transformer, rectifier and smoothing capacitor. It's important to get the terminology right.
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Old 3rd Nov 2009, 12:09 pm   #7
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Default Re: Car 8 track advice!

Quote:
Originally Posted by ben View Post
In my experience the metal chassis is common return for the speakers and negative for the DC input. Grey and green, as I recall, are the colours often used for speaker left and right lines. Red for 12v, but trace it back to double check.
many thanks for the very swift reply!

Yes thats what i wodl have thought but the gauge of the wires seemed to militate against that...and with pcb's its a bit hard to trace back.

Also, i am confused by thre being 4 wires if thre is a common chassis return - wouldnt thre be 3 wires only then?

If i power up by trial and error, will i blow something?

thansk again
RDS
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Old 3rd Nov 2009, 12:10 pm   #8
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Default Re: Car 8 track advice!

Quote:
Originally Posted by Station X View Post
In that case what you have is a power supply incorporating transformer, rectifier and smoothing capacitor. It's important to get the terminology right.
indeed yes! thanks again!
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Old 3rd Nov 2009, 12:10 pm   #9
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Default Re: Car 8 track advice!

Exactly! Technically, a transformer converts AC to AC, whereas what you're describing is really a "power supply" incorporating diodes, capacitors, and possibly regulators.

A lot of non-technical people do tend to use the terms interchangeably though.

Nick.
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Old 3rd Nov 2009, 12:12 pm   #10
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Default Re: Car 8 track advice!

Quote:
Originally Posted by Nickthedentist View Post
I would recommend a regulated or stabilised 12v DC supply rated at about 2A or so. Maplin will have something suitable. If you use a CB supply, make sure you fuse it at about 2A as they can produce serious amounts of current if you have a short circuit somewhere.

You can sometimes tell whether it's -ve or +ve earth by looking for a biggish electrolytic capacitor inside. If its negative connection is connected to the chassis, then it's -ve earth and vice versa. I must say that "Mustang" sounds a bit American to me (but I know nothing about cars!) and they favoured +ve earth there, so do double check.

When you first power it up, it might be worth doing so with a car indicator bulb in series, so that if something goes horribly wrong, the bulb will absorb the current and light, rather than a cloud of smoke being emitted.

Could you post a picture of the unit, inside and out? This should enable us to tell whether it's got an inbuilt power amp or not.

N.
great advice!

yes i wanted to post a picture: can you piont me to the instructions as to how to do this?

cheers

N
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Old 3rd Nov 2009, 12:13 pm   #11
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Lightbulb Re: Car 8 track advice!

Another thought... Use a multimeter set to its lowest ohms range to see if any of the four connections are connected directly to the chassis
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Old 3rd Nov 2009, 12:14 pm   #12
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Default Re: Car 8 track advice!

Quote:
Originally Posted by Nickthedentist View Post
Exactly! Technically, a transformer converts AC to AC, whereas what you're describing is really a "power supply" incorporating diodes, capacitors, and possibly regulators.

A lot of non-technical people do tend to use the terms interchangeably though.

Nick.
mea culpa! - even the bods at Maplin seem to do that too!
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Old 3rd Nov 2009, 12:20 pm   #13
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Default Re: Car 8 track advice!

I've just checked the cassette player in my classic car. The colours are as follows:-

Red =Power (+12V)
Green=Left.
Grey=White
Black=Speaker Common.
Case=Earth (0V ie battery negative).
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Old 3rd Nov 2009, 12:26 pm   #14
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Default Re: Car 8 track advice!

Quote:
Originally Posted by Station X View Post
I've just checked the cassette player in my classic car. The colours are as follows:-

Red =Power (+12V)
Green=Left.
Grey=White
Black=Speaker Common.
Case=Earth (0V ie battery negative).
thanks Graham

i bought it for my classic too but cannot find a good place to put it - hence use in the garage!

i'll hook it up that way then and use a 6 pin so as to replicate the earths.

cheers

RDS
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Old 3rd Nov 2009, 7:24 pm   #15
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Default Re: Car 8 track advice!

this is a Japanese unit, Mustang was one of many generic names that were slapped on this kind of players.

Like many japanese players it has the round 4 pin socket, the colours are always the same: red= +12v, green=left spk, grey=right spk, black=chassis ground, instead of replacing the socket and ruining the originality of the player, why don't you just stick 4 stripped wires of suitable size in the socket holes?

if you check with a multimeter you'll see that the black wire measures dead short to the metal chassis.

The ground in 70s players is almost always negative, with some earlier units having a selectable ground polarity, as most cars by then had negative ground 12v electrics, only really archaic cars like early vw beetles have 6v and/or positive ground electrics

Last edited by Jimmyhaflinger; 3rd Nov 2009 at 7:35 pm.
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Old 6th Nov 2009, 3:44 pm   #16
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Default Re: Car 8 track advice!

Great thanks! in fact I bought the unit for my Mustang but think it will be better on the garage shelf.

I don't really like ruining original things either, so better still can anyone point me in the direction of the female plug that I need (!)? It'll be a more permanent fix then.

Thanks again

RDS

Last edited by Brian R Pateman; 6th Nov 2009 at 4:23 pm. Reason: Quote not needed - removed.
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Old 6th Nov 2009, 8:56 pm   #17
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Default Re: Car 8 track advice!

I think the connector is probably a generic Japanese part used on a lot of these 70's tape players but not easily available from the usual UK suppliers. Scrap units with connectors & cables occasionally turn up in boot sales, ebay etc. Maybe you could try a request in the 'wanted' section of this forum.
As an aside, if you want a tape player for your Mustang, try U.S. ebay, there's loads of radio/tape units on there. I don't know what year your car is but something from the late 70's would be late enough to have a tape but early enough to have styling to suit 60's/70's dashes.
Cheers,
Mark.
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Old 7th Nov 2009, 3:35 pm   #18
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Default Re: Car 8 track advice!

I'd just change the socket out to a more readily available DIN plug. that is basically a 'period modification'. it's not as it it is on view and would ruin anything aesthetic, is it?
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Old 8th Nov 2009, 5:56 pm   #19
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Default Re: Car 8 track advice!

Thaks

i'l look out for a connector but as the mod will be reversible, in the meantime i will try a DIN connector, just to get the unit working!!!

cheers


RDS
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Old 8th Nov 2009, 7:59 pm   #20
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Default Re: Car 8 track advice!

As already stated the 8 track power supply should be fused at 2amps. It is worth checking the output of your Piano power supply could be less than this typically around 1amp in which case you might damage the power supply. More experienced members might like to add more. John
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