[Guest]

I purchased this Philco 48-250: As a practice set. My first.

[Image: http://i209.photobucket.com/albums/bb212...250004.jpg]

And have a question regarding converting to a polarized ac cord. I have received differing opinions on whether or not to use a polarized power cord as a safety factor in this AC/DC chassis. Some say absolutely and some say keep it as originally designed. Also need to know if I use the polarized cord should I connect the + lead to the on/off pot or to the rectifier tube as the original non-polarized cord. Seen here:

[Image: http://i209.photobucket.com/albums/bb212...250015.jpg]

According to Phil's Old Radios I should follow the procedure found here:
http://www.antiqueradio.org/safety.htm

Any opinions?

Thanks for your help.

Mark

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[Ron Ramirez]

Hi Mark

You should definitely follow the procedure on Phil Nelson's website (via the link you provided above) if you plan on using your radio. It will make it safer overall by making the HOT lead of the AC line switched instead of the neutral.

With the neutral switched and the HOT lead connected direct to the rectifier tube, the set is basically HOT all of the time. Using Phil's modification, the set is only HOT when the power switch is on.

Simplified explanation. I think you get my drift.

Edit: That is a very good set for practice. No rubber-covered wires - Philco used improved plastic insulation on the wires of their postwar models which has held up very well over the years. Not a lot of tubes, so it is not a complicated set. Best of luck with it...and be safe!

[Guest]

Thanks,Ron. Another piece of advice that I have read is to add a 1 amp fast blow fuse on the + side of the power cord before the connection to the switch. Good idea?
Mark

[Ron Ramirez]

Personally, I would not worry about a fuse in that set. But if you do add one, a 1 amp slow-blow fuse is better than a fast blow fuse, in my opinion.

[Texasrocker]

Just my .02 here, but I think replacing all those old wax bypass caps & the electrolytics would be a great idea! Polarity of the AC line was never closely observed by mfgrs back in the day when these AC/DC sets were originally made. Orig AC cords had no large-spade on one side, polarity was determined by how the cord was actually plugged into the AC socket. Didnt make much difference back then if the end-user plugged the radio in "bass-ackwards"for proper polarity reasons?. Always be careful when touching or servicing a vintage AC/DC type chassis! Use a AC line "isolation transformer" while working on the chassis if possible! Using a 1amp fuse for safety on either side of the AC line is better than none at all, but not necessary in most cases except for added safety for the person restoring these vintage type chassis'. I always use the old theory of using the "one hand" method when not using a isolation trans when servicing the old "potentially-lethal"AC/DC type chassis! Just good practice, and keeps the restorer in the safe zone! I certainly wouldnt want any of my vintage restored Arvin, Kent, Silvertone, metal midget AC/DC sets near the bathtub, or kitchen sink, period! Those live vintage radio AC/DC chassis could be lethal as a old rattlesnake bite in certain situations indeed!! If you wire the polarity "correct" to todays recommended standard, then find out the AC plugs in your house was originally wired in reverse of electrical"code" ( many homes are!!),... then, your back to square-one unless you own a "AC polarity" checker and spend time to trace down every AC socket in your home back to the breaker box. The good thing about AC is it always works! The bad thing about modern day AC, is voltage runs to high, and your plugs in your house could be wired "bass-ackwards" in many rooms for overall correct "phasing" on the "larger spade"!! Reckon?

[Guest]

Texasrocker, thanks, I have purchased the replacement wax caps and electrolytic caps. I do have an iso trnfmer and a back pocket. Since this is a starter/practice set I will be doing everything for the first time on this one . Your suggestions are greatly appreciated.

Mark