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orginal BMC radio

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bluegrass john

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Anyone know if it is possible to change polarity in an orginal BMC to function in a negative ground Healey BJ8 without spending more than the radio is worth ??

Thanks for any advice I can get!!

John
 
Thanks Bob..............do I find the plug on the outside of the unit or is it internal? I know I have seen some later BMC radios that have a dual slide switch to select the correct polarity. The unit I am looking at purchasing does not have that switch that I can see externally.

Thanks so much for your time,

John
 
Plug is on the outside of the radio. If you do a Google search for "bmc radio polarity" and select images, there are some nice photos of just what you need a few rows down.
Bob
 
Hi John,

During the span of time multiple models of BMC radios were availability in a number of cars. I would suggest you be very careful that the radio you have can be polarity switched. About a year after the delivery of my new BJ8 in 1964, I installed a new AM BMC radio that remained installed until converting to negative ground about 20 years after. At that time, I attempted to convert the original BMC radio but found, verified by an expert, that the polarity could not be easily changed. The reason given was as has been mentioned, that the case the ground for the radio as is the antenna. Modification would require the internal boards be changed substantially to accept the change. As you indicated, other models of BMC radios had the internal circuitry isolated from the case and, as such, could be altered to operate in a negative ground environment.

I am not sure what BMC model radio you have but I would be very careful thinking it will be easy. Although I still have my original BMC radio, when changing car polarity, I decided it would be far safer if I acquire a negative ground radio that would accept the clear plastic BMC display and install it instead of risking and trying to modify the original. The original has remained on the shelf for over 30 years and I will probably never reconvert my car back to positive ground. The replacement negative ground radio, with the BMC display, is still installed in my original console and is also sitting on the shelf waiting for the time when I ever think of going back.

Bob may be correct and your model may be easily convertible...or maybe not.

Good luck,
Ray (64BJ8P1)
 
I think you have offered some sound advice; I will take heed and perhaps the way to go is to purchase a radio with the slide switch that offers dual polarity. They are occasionally available on e bay and I am told certain models will fit like a glove !!

Regards.
John
 
bluegrass john said:
I think you have offered some sound advice; I will take heed and perhaps the way to go is to purchase a radio with the slide switch that offers dual polarity. They are occasionally available on e bay and I am told certain models will fit like a glove !!

Regards.
John
Click to expand...

:iagree:---or purchase a later NEG Ground AM / FM look alike radio, as the power output and music quality of the old BMC radios is not that good.
 
I attempted to convert the original BMC radio but found, verified by an expert, that the polarity could not be easily changed. The reason given was as has been mentioned, that the case the ground for the radio as is the antenna. Modification would require the internal boards be changed substantially to accept the change.

Well that intensive a modification is generally not required:
It can be accomplished by simply isolating the radio case and the antenna from chassis ground.
However, this method is not consider safe or recommend.
 
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