UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 25th Aug 2010, 6:48 pm   #21
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default 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?
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is online now  
Old 25th Aug 2010, 7:51 pm   #22
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,528
Default Re: Old car radio - how to change polarity?

Quote:
Originally Posted by kalee20 View Post
Actually, I'm surprised the 1947 Riley isn't positive earth itself.

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
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline  
Old 25th Aug 2010, 8:29 pm   #23
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
Default 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).
kalee20 is offline  
Old 26th Aug 2010, 9:17 am   #24
Geoff 555
Heptode
 
Geoff 555's Avatar
 
Join Date: Jan 2008
Location: Bristol, UK.
Posts: 981
Default 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.
Geoff 555 is offline  
Old 26th Aug 2010, 9:27 am   #25
ppppenguin
Retired Dormant Member
 
ppppenguin's Avatar
 
Join Date: Dec 2003
Location: North London, UK.
Posts: 6,168
Default 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.
ppppenguin is offline  
Old 26th Aug 2010, 10:46 pm   #26
'LIVEWIRE?'
Rest in Peace
 
'LIVEWIRE?''s Avatar
 
Join Date: Mar 2006
Location: N.W. Oxfordshire(Chipping Norton)
Posts: 7,306
Default 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!
'LIVEWIRE?' is offline  
Old 26th Aug 2010, 10:57 pm   #27
murphyv310
Dekatron
 
murphyv310's Avatar
 
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
Default 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!).
__________________
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
murphyv310 is offline  
Old 2nd Jan 2011, 4:43 pm   #28
Rupert Buryan
Retired Dormant Member
 
Join Date: Jul 2010
Location: Penzance
Posts: 1
Default 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!
Rupert Buryan is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:27 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.