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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 6:56 am 
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Location: USA
Hi Folks -<P>Got a hold of an AC/DC radio this weekend - very small cool looking 1949 Emerson 587-B. Now if I want to cool the hot chassis, which wire on the power cord gets attached to which plug blade (wide or narrow)? Obviously, the AC line splits inside the radio and one looks like it goes to the switch and the other a tube base. This radio has 4 metal screws external to the cabinet that go directly to the chassis - so I want to make sure I make this safe to the touch. Maybe plastic screws would help?<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 7:13 am 
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Location: Las Cruces, NM
The wide blade on a polarized plug is neutral. As for the screws, the chassis may not be circuit ground. Check the schematic, or use a meter.<P><BR>------------------<BR>Joe Gray


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 7:35 am 
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These radios usually have one power wire going directly to the rectifier tube, and the other to one side of the power switch (call this Terminal 1), with the other side of the power switch going to ground. What you need to do is to rewire the radio as follows. Remove the old power cord connection to the switch (at Terminal 1), and in its place connect the narrow (hot) prong of the polarized plug to the power switch). Disconnect the wire on the other side of the power switch (call this Terminal 2) that goes to ground, and disconnect the other half of the old power wire that is connected to the rectifier. Run a wire between the two points that you have just disconnected the wires from (i.e. between Terminal 2 of the power switch and the rectifier). Remove the remaining piece of wire (now connected only to ground) that used to be connected to Terminal 2 of the power switch and ground. Connect the side of the new power cord having the larger (ground) plug to ground at a convenient point (usually the ground point where you just removed the wire that had connected ground to Terminal 2 of the power switch will work fine.) (BTW, the larger prong of the plug will be connected to the grooved side of the power cord.)<P>What you want is power from the hot (small) prong of the plug to go to the power switch, and then to the rectifier. The ground wire from the larger prong should go to ground on the radio. This way the radio will be safe when turned on or off, assuming the house is wired correctly.<P>Bob<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 11:56 am 
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Radio wrote:
<font>quote:</font><HR>Originally posted by sofaslug:<BR><B>These radios usually have one power wire going directly to the rectifier tube, and the other to one side of the power switch (call this Terminal 1), with the other side of the power switch going to ground. What you need to do is to rewire the radio as follows. Remove the old power cord connection to the switch (at Terminal 1), and in its place connect the narrow (hot) prong of the polarized plug to the power switch). Disconnect the wire on the other side of the power switch (call this Terminal 2) that goes to ground, and disconnect the other half of the old power wire that is connected to the rectifier. Run a wire between the two points that you have just disconnected the wires from (i.e. between Terminal 2 of the power switch and the rectifier). Remove the remaining piece of wire (now connected only to ground) that used to be connected to Terminal 2 of the power switch and ground. Connect the side of the new power cord having the larger (ground) plug to ground at a convenient point (usually the ground point where you just removed the wire that had connected ground to Terminal 2 of the power switch will work fine.) (BTW, the larger prong of the plug will be connected to the grooved side of the power cord.)<P>What you want is power from the hot (small) prong of the plug to go to the power switch, and then to the rectifier. The ground wire from the larger prong should go to ground on the radio. This way the radio will be safe when turned on or off, assuming the house is wired correctly.<P>Bob<P></B><HR>
<P>Hi Bob,<BR>Great post.<BR>I am wondering if this would work on any radio?<BR>I have a couple of sets I have thought about doing this to.<BR>Radio<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 4:31 pm 
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Location: Arlington, VA USA
Radio,<P>I rewire all my AC/DC radios this way. The polarized plug may not be time period appropriate but for me safety is more important. <P>This technique may produce more hum as there will be a higher voltage potential in the power switch, which on most radios, is also the volume control. This will be radio dependent. I haven't noticed a problem with this on any of mine, yet.<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 4:33 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Buenos Aires, Argentina
I do as Bob says with all my AA5 ac/dc, transformerless radios, is the safest way, if correctly plugged, the chassis can never get hot. <P>For transformer radios I guess you should look at the schematics but in the majority of cases that I have seen, it makes no difference at all since power goes straight to the transformer. <P>A last comment: in some large radios, I add a fuse. I know it makes the radio look not original, but I have had many bad experiences so I take no chances. I use the cable type fuse which can be easily hidden under the chassis <P>Mario<P>------------------<BR>Pro Collector


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 5:48 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Jim Thorpe, Pa., USA
If you are concerned with authenticity, an older type plug can be made polarized quite easily. I take a short piece of 14 or 16 Ga. wire and solder it to one edge of the prong I want to be the wider one. Once the solder cools I dress this down with a file so that it fits well in the wide slot of the outlet. <P>------------------<BR>Tom Lager


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 6:14 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Central Ky.
On polarized plugs; I have a 1930's Atwater Kent on which I wanted a cloth cord and appropiate plug. I got the reproduction cord and the rectangular old style nonpolarized plug from Radiodaze. The plug prongs had holes already in them. I drilled the hole larger on one prong and then used a nail set (tapered punch) to stretch the width of the prong to fit the neutral side of the plug only. <P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 7:35 pm 
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sofaslug wrote:
<font>quote:</font><HR>Originally posted by Radio:<BR><B> <BLOCKQUOTE><font>quote:</font><HR>Originally posted by sofaslug:<BR>These radios usually have one power wire going directly to the rectifier tube, and the other to one side of the power switch (call this Terminal 1), with the other side of the power switch going to ground. What you need to do is to rewire the radio as follows. Remove the old power cord connection to the switch (at Terminal 1), and in its place connect the narrow (hot) prong of the polarized plug to the power switch). Disconnect the wire on the other side of the power switch (call this Terminal 2) that goes to ground, and disconnect the other half of the old power wire that is connected to the rectifier. Run a wire between the two points that you have just disconnected the wires from (i.e. between Terminal 2 of the power switch and the rectifier). Remove the remaining piece of wire (now connected only to ground) that used to be connected to Terminal 2 of the power switch and ground. Connect the side of the new power cord having the larger (ground) plug to ground at a convenient point (usually the ground point where you just removed the wire that had connected ground to Terminal 2 of the power switch will work fine.) (BTW, the larger prong of the plug will be connected to the grooved side of the power cord.)<P>What you want is power from the hot (small) prong of the plug to go to the power switch, and then to the rectifier. The ground wire from the larger prong should go to ground on the radio. This way the radio will be safe when turned on or off, assuming the house is wired correctly.<P>Bob<P></B><HR></BLOCKQUOTE><P>Hi Bob,<BR>Great post.<BR>I am wondering if this would work on any radio?<BR>I have a couple of sets I have thought about doing this to.<BR>Radio<P><HR>
<P>I think this would work on any radio that's originally wired with the power switch on the ground side. The possibility of hum is an issue, as was pointed out, but it's never made a difference on the radios I've worked on. You can always check before had by operating the radio with the original power plug inserted into the wall jack one way, and then the other. If there's no hum either way, then you're fine.<P>I've even done this modification on radios like my GE L570, which was UL approved and had a common ground that was isolated from the chassis -- mainly because I wanted the hot wire going to the power switch first so that there were fewer "hot" thiings under the chassis with the power off (I like to keep my radios plugged in all the time).<P>Bob<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 9:44 pm 
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Location: Little Fort (a.k.a.) Waukegan, IL
Quote by mario2 "For transformer radios I guess you should look at the schematics but in the majority of cases that I have seen, it makes no difference at all since power goes straight to the transformer."<P><BR>Switch should ALways be in the hot side of the line.<P>------------------<BR>Tony


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Tue 19, 2005 11:04 pm 
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Location: PA, USA
J Matahratz wrote:
<font>quote:</font><HR>Originally posted by lagert:<BR><B>If you are concerned with authenticity, an older type plug can be made polarized quite easily. I take a short piece of 14 or 16 Ga. wire and solder it to one edge of the prong I want to be the wider one. Once the solder cools I dress this down with a file so that it fits well in the wide slot of the outlet. <P></B><HR>
<P>I just split the end of the prong down the middle with diagonal pliers. This will widen it just enough so that it fits only the wide slot of the wall receptacle.<P><P>------------------<BR>Steve


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Wed 20, 2005 12:09 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Carlotta,Ca
Thanks guys,<BR>I was thinking of doing this to an older Crosley I have.<BR>I found some neat plugs that are polarized but they look like older style plugs at the hardware store.<BR>So I should be able to keep it looking original.<BR>One quick question aimed at mario2 but anybody can answere.<P>Is adding a fuse necessary in a radio? and if it is where do you put it and how do you know what size fuse to run?<BR>Thanks.<BR>Radio<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Wed 20, 2005 2:59 am 
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Location: Arlington, VA USA
I don't fuse AA5's because if there was a short on B+ or in the series heater string one the heaters would open acting like a fuse so I don't think adding one will buy you much.<P>I always add a fuse to transformer sets and try to locate it between the power switch and transformer, so the hot lead from the power cord runs directly to the switch then switch to fuse and fuse to transformer. Neutral lead to the transformer. This way the only thing hot when the radio is off is the one switch terminal minimizing accidental shocks while poking around.<P>When I add a fuse I use the power rating on the radio or measure it. I then add 50 to 100% to the fuse rating. So if a radio is rated at 60 watts (1/2 amp) I would use a 3/4 amp to 1 amp fuse and usually the fast blow type. Never had a nuisance blow yet. My goal is to protect the power transformer in case of a fault. If the original manufacturer added this feature to begin with there would be a lot less blown transformers out there.<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Wed 20, 2005 3:20 am 
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Location: USA
Thanks guys - this is all great information. Remember - safety first!<P>Nuke (I'm radio active - get it?)<P>------------------<BR>


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 Post subject: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Wed 20, 2005 6:02 am 
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Thanks for the explainations.Very helpful.<BR>Radio<P>------------------<BR>


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 Post subject: Re: Polarized Plug Installation on AC/DC Radio
PostPosted: Apr Sat 16, 2011 2:34 am 
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Joined: Feb Fri 25, 2011 11:21 pm
Posts: 52
sofaslug wrote:
These radios usually have one power wire going directly to the rectifier tube, and the other to one side of the power switch (call this Terminal 1), with the other side of the power switch going to ground. What you need to do is to rewire the radio as follows. Remove the old power cord connection to the switch (at Terminal 1), and in its place connect the narrow (hot) prong of the polarized plug to the power switch). Disconnect the wire on the other side of the power switch (call this Terminal 2) that goes to ground, and disconnect the other half of the old power wire that is connected to the rectifier. Run a wire between the two points that you have just disconnected the wires from (i.e. between Terminal 2 of the power switch and the rectifier). Remove the remaining piece of wire (now connected only to ground) that used to be connected to Terminal 2 of the power switch and ground. Connect the side of the new power cord having the larger (ground) plug to ground at a convenient point (usually the ground point where you just removed the wire that had connected ground to Terminal 2 of the power switch will work fine.) (BTW, the larger prong of the plug will be connected to the grooved side of the power cord.)<P>What you want is power from the hot (small) prong of the plug to go to the power switch, and then to the rectifier. The ground wire from the larger prong should go to ground on the radio. This way the radio will be safe when turned on or off, assuming the house is wired correctly.<P>Bob<P>------------------<BR>


I have a question about this. The Silvertone I have is wired as follows. The power cord leads go exactly as above with the rectifier connection on pin 3. But terminal two of the power switch has a wire going to a transformer. And another wire going to the rectifier, connected at pin 5.

How do I wire my new cord to make it safe?


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 Post subject:
PostPosted: Apr Wed 20, 2011 3:31 am 
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Have I exceeded my quota of dumb questions? LOL

I'm flying out tomorrow for San Antonio to witness my Daughter's graduation from USAF Basic Training . Taking a copy of Keith Henney's "Principles of Radio" from 1942 to read on the plane. Will be nice to have time to read for awhile.

After re-wiring the entirety of my Silvertone 7111, I'm left with replacing the power cord and the can capacitors.

If I could get an answer to the question in my previous post, I would be most grateful.


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 Post subject:
PostPosted: Apr Wed 20, 2011 6:30 am 
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Your Silvertone is a transformer powered set. The transformer effectively isolates the voltages present in the radio from the AC power line, so the gist of this thread (AA5 safety) doesn't apply to your set.

Pin 3 of the rectifier tube socket is a tie point, it doesn't connect to any element in the tube. The set is fine wired as is, but if you want to use a polarized plug, tie the lead that goes to the narrow blade of the plug to the on-off switch. That way, the switch will interrupt the hot leg into the primary winding of the transformer when 'off'.


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 Post subject:
PostPosted: Apr Mon 25, 2011 5:33 pm 
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Thank you, David.


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 Post subject: Re: Polarized Plug Installation on AC/DC Radio
PostPosted: Dec Fri 30, 2011 11:37 pm 
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Location: York, PA
Ok- New guy needs a little help here.
I've just finished recapping an old Westinghouse Astra. I now want to complete the job by installing a new polarized power cord. I have read this thread and a few others that all instruct me to do the same things. My confusion comes about with the fact that I have 3 wires attached to the ground terminal of the on/off switch. One goes to the ground side of the electrolytics, one goes to the output tube, and the third wire goes to a resister that then attaches to the side of the on/off switch. The other terminal of the on/off switch just has the old power cord lead. The other lead of the old power cord goes to the rectifier.
I am confused about what to do about all of the ground wires currently connected to the on/off switch (at "terminal 2") once I remove them and solder in the ground lead of the new power cord (wide blade of plug) and the new wire going to the rectifier tube. Do I need to create a new chassis ground point to attach all of these wires to?

_________________
Bill W


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