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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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25th Aug 2010, 6:48 pm | #21 |
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Re: Old car radio - how to change polarity?
There's still a possiblility the radio could be converted if we knew what model it was.
Given that your friend is a purist I assume it's a valve model?
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25th Aug 2010, 7:51 pm | #22 | |
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Re: Old car radio - how to change polarity?
Quote:
Actually it is! Or should be. If the guy's a purist and it's now negative earth, then flashing the dynamo is the only way to go, with the advantage of being zero cost as well See general description on first page and circuits at end of this reference: http://www.rileywa.org.au/RM_Manual/rm_wm_section_N.pdf
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25th Aug 2010, 8:29 pm | #23 |
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Re: Old car radio - how to change polarity?
So the Riley being its un-original negative earth doesn't tie up with him being a purist. If it was changed back to positive earth, then it would suit the radio straight away, and everything would be original.
Or has it got electronic ignition fitted, or something esle after-market which demands negative earth? (Though I made two transistor-assisted ignition units to suit my positive-earth Land Rover and Morris Minor. Unconventionally I had the coils connected direct to chassis, but they worked well). |
26th Aug 2010, 9:17 am | #24 |
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Re: Old car radio - how to change polarity?
Hello chaps, much thickness but I am struggling to work this one out, assuming that the radio is not totally isolated ( problems with aerial insulation etc.) then if the radio chassis is connected to chassis, negative earth, if I have read things correctly the DC-DC positive to chassis ?? and the negative to radio supply then that means that the radio is being fed with 2 negative supplies.
It is probably very simple but the more I look at it the more I find it totally confusing. ERR sorry. Cheers. Geoff. |
26th Aug 2010, 9:27 am | #25 |
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Re: Old car radio - how to change polarity?
Since the input and output are totally isolated from each other you can think of the DC-DC converter as a separate battery, dedicated to running the radio. Hence you can connect the radio chassis to the car chassis, then power the radio from a "battery" with whichever polarity it needs.
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26th Aug 2010, 10:46 pm | #26 |
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Re: Old car radio - how to change polarity?
A (small)point-many early Radiomobile, Motorla, and other makes of Car Radio could have their polarity(and sometimes voltage) changed via internal soldered links. If it's a VALVE
radio with a Non-Synchronous(4 or 5 pin usually)Vibrator then it can be used on either polarity without any changes. However, like kalee 20, I'm surprised that a '47 Riley isn't Positive Earth. Thought ALL vehicles were in those days! |
26th Aug 2010, 10:57 pm | #27 |
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Re: Old car radio - how to change polarity?
Speaking to a Riley RME owner he says all Rileys of the era ARE positive earth!
Perhaps someone has their wires crossed (pardon the pun!).
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2nd Jan 2011, 4:43 pm | #28 |
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Re: Old car radio - how to change polarity?
The Riley RM's ARE positive earth - I have owned a 1 1/2 and a 2 1/2 - twice, which I am now rebuilding second time round as a drop-head and converting to NEG earth for a modern very much cheaper alternator, than a pos earth alt. Additionally, the chap who is re-building my valve wireless insists I convert to neg earth, as the old converters were hopeless, he tells me, and he is going to make the thing get FM!
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