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Good morning. I want to put a polarized plug on my Philco 39-30. I'll be putting in a fuze once I'm sure the power transformer is good as well.
Question: I want to confirm that the hot side of the wall power line connection goes to the side of the Bakelite cap with the .10uf cap that goes onward via a red wire to the on/off switch, and that the ground should attach to the Bakelite cap where the black wire running to the power transformer goes.
When re-wiring the set to get rid of flaking wire, I already found some wiring colors that weren't right (red wire used on an obvious ground lug connection) and I want to be sure.
Regards,
Clarence
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imacdaddy757 Wrote:Good morning. I want to put a polarized plug on my Philco 39-30. I'll be putting in a fuze once I'm sure the power transformer is good as well.
Question: I want to confirm that the hot side of the wall power line connection goes to the side of the Bakelite cap with the .10uf cap that goes onward via a red wire to the on/off switch, and that the ground should attach to the Bakelite cap where the black wire running to the power transformer goes.
When re-wiring the set to get rid of flaking wire, I already found some wiring colors that weren't right (red wire used on an obvious ground lug connection) and I want to be sure.
Regards,
Clarence
There isn't any point in installing a polarized plug on an AC set, thanks to the transformer the chassis is alreay isolated from the power line. What I would do is change the electrical orientation of the line capacitor, reconnect it so one side of the cap is connected to the radio side of the power switch so it is out of circuit while the set is turned off.
Regards
Arran
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Thanks, Arran. I've done about 30 AC/DC sets but this is my first AC set. Thanks for the tip on moving the cap.
Regards,
Clarence
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I don't think it is a good idea to move the line capacitor to the other side of the switch. By doing so, you could have line potential on the chassis when the radio is turned off, depending on the orientation of the wall plug. As it is now the chassis is at one half line voltage. Granted the current would be quite limited and wouldn't be a safety concern, but it could give a little tickle. My recommendation would be leave the radio as it was designed.
Steve
M R Radios C M Tubes
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The first thing I always do is install a new power cord with a polarized plug and an inline fuse. I agree with moving the line capacitor to the other side of the on-off switch, along with the fuse. I also like to take the additional measure and replace the filter cap/caps with safety capacitors.
The 38-10 & 40-150 I recently worked on had the bakelite block with two .01uf caps on the input power, so I replaced them with Y2 safety capacitors. This ensures that there are no issues as could be the case with a non-polarized plug and its orientation. Even though AC sets have transformers, it doesn't hurt to put in an added margen of safety. I think if you look around and read other articles about this very issue you will find a polarized plug doesn't hurt and is recommended.
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I looked at the schematic for this set, it appears that there are actually two line caps, one situated between each outside leg of the power transformer primary and common negative, so you could only move one to the radio side of the power switch. What I pictured was what you typically see which is one capacitor connected across both legs of the primary or power line. I don't really like this arrangement but it is somewhat safer in that you don't have the power line directly connected across the caps, but is one shorts out it could do some exciting things, this is one case in which I would go the "Safety" cap route . Most of the CGE and RCA sets that I work on don't have a line capacitor, they use an electrostatic shield inside the power transformer instead. Again I don't know what a polarized plug is going to do for you in this case.
Regards
Arran
