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TR4/4A Radio/CD player install help in tr4 pos ground

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steve_sims

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Howdy All, Just got a crazy idea about installing radio/cd player in the TR4. Car is Positive ground. I am an electrical idiot. Can i put in neg. ground radio in pos. ground car? HOW???? Thanks Steve
 
steve_sims said:
Howdy All, Just got a crazy idea about installing radio/cd player in the TR4. Car is Positive ground. I am an electrical idiot. Can i put in neg. ground radio in pos. ground car? HOW???? Thanks Steve
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Only if you like smoke. You could try to isolate it from the car's ground which would allow you to attach the hot lead to the radios ground and the radios power lead to the cars ground, but not easily done. Better to convert to a negative ground.
 
Converting the car to negative ground is easy. Converting the radio to positive ground is somewhere between difficult and impossible.

Trying to run it isolated is just asking for trouble, IMO. Note that the outer sheath of the antenna lead is connected to the antenna base (bolted to the car body) as well as the radio case, which is connected to the negative lead. Also the antenna whip is usually grounded through the radio's electronics, so accidentally shorting it to ground can damage the radio.

Converting the car to negative ground is by far the easiest and most trouble-free way to go. There are more details at
https://www.vtr.org/maintain/negative-ground.shtml
but basically you switch the connections at the battery, ignition coil, and ammeter. Then repolarize the generator and you're done. It really is that easy.

One other option not yet mentioned is a "polarity converter", which is basically a power supply that takes
-12v and turns it into +12v. Using that, the radio can be grounded as usual and work normally. The downside is that polarity converters are expensive and it's hard to find one that delivers enough power for many modern CD players.

Randall
 
Thanks, If i decide to add the radio, i will go ahead and change to neg. ground. I guess i'll have to get a muffler too. Its running a gutted glasspack now. Sounds great but gets real old if you want to hold a conversation with the passenger. Thanks Again, Steve
 
FWIW, I was very pleased after taking my TR3A to a local muffler shop. He installed a new glasspack and tailpipe for less than just the mufflers would have cost from an LBC vendor. Sound was much mellower than before but still just a bit loud for my taste, so I put a downturned chrome tip on the new tailpipe, which got it just right.
 
Little tip on a modern radio in the old cars. Make sure you hook the power and Memory wires as directly to the battery as you can (fused of course) Otherwise, at idle, when the generator is not putting out any voltage, and the battery voltage drops off, the radio will wink out and come back on without all your presets and time.
It get's annoying after a while.
Mine in my TR4A was constantly doing that. upgrading to an alternator would have fixed that, but I diden't wanna.
 
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