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Replacing a Power cord - Printable Version

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Replacing a Power cord - jrc0109 - 12-07-2018

The original power cord on my Model 51 radio was replaced a long time ago. If I were to replace it again, should it be replaced with a three wire cord so that the grounding wire would not be a separate wire, but part of the power cord?
Thanks.
John

RE: Replacing a Power cord - Radioroslyn - 12-07-2018

Personally I like separate grounds (chassis not connected to the outlet ground)as they can be noisy. Use a reproduction cloth cord.

RE: Replacing a Power cord - Chas - 12-08-2018

I don't add chassis grounds via the power cord either. Same reason, ground to the panel will likely travel some distance with all the noises of the AC line.

Chas

RE: Replacing a Power cord - jrc0109 - 12-09-2018

Thanks very much. I appreciate the advice.
John

RE: Replacing a Power cord - jcassity - 12-15-2018

to be slick, use a power cord that has a fuse built into the plug.
has a little slide door to which you can remove and replace the fuse.

RE: Replacing a Power cord - mwoodruff - 12-27-2018

Nice idea for the fuse, where can I get such a plug?

And for obsessive-compulsive purposes only, what color was the original cloth-covered power cord? Brown, brown-yellow?

And how long?

My "find" (16b Cathedral) only has the stub of a cord, so if I'm going to restore, might as well do it right.

RE: Replacing a Power cord - jcassity - 12-27-2018

i have a cord from another item from the past.

the easy place to find the plug i speak of is on christmas lights.

i am sure i would be able to find the plug cord from another item but i am betting i wont like the price.

so... i am doing a quick study on the christmas light plug.
so far i am not impressed because the christmas light plugs are not polarized,,, but the christmas light plug has TWO fuses!

this option is going to be very very very inexpensive to integrate into radios.


this is like the one i harvested from something else,, i think it was from an old box fan??
http://www.nbwell.com/products_detail.aspx?pid=524&id=779&page=1



these are very nice, not so expensive but the darn thing has no onboard fuse....
https://www.oogalights.com/Leviton-Black-Hinged-Cord-Plug-15A-125V.aspx?_vsrefdom=oogalights&gclid=EAIaIQobChMInbzhocrA3wIVCglpCh32dQrgEAQYAyABEgJqIvD_BwE#features

i cant tell if this darn thing has the fuse or not
https://www.1000bulbs.com/product/172795/CMS-MALEPLUG2G.html?gclid=EAIaIQobChMInbzhocrA3wIVCglpCh32dQrgEAQYASABEgIe3_D_BwE#detail-tabs

then there is this what the industry calls "VAMPIRE ZIP CORD PLUGS " which has a fuse provision and its 90deg style so to speak...but ... i dont like the idea of insulation penetration dependent cords ... but... it might be good nuff for what we do?? pack of 12 for cheap
https://www.actionlighting.com/spt-1-spt-2-fused-male-vampire-zip-cord-plugs-white-pack-12-plugs-100sptplugf-white/


tractor supply has a bakalite rendition of the old USA old radio plug that has a onboard fuse,, looks like NOS usa stuff from yesteryear but made in china.

RE: Replacing a Power cord - PhilcoPhan1936 - 12-27-2018

I buy a variety of the round vintage style reproduction plugs here. They have the Acorn, faceted, MCM and "Deco" styles. I usually get black or brown.

https://vintagewireandsupply.com/plugs-connectors/

For cord, I get brown 25' and cut to 6'3", so I get 4 cords from a roll.

http://www.radiodaze.com/brown-braid-cloth-18awg-power-cord-item-pwc-1a/

RE: Replacing a Power cord - mwoodruff - 12-31-2018

The original power cord on my 16b is missing the plug, but is otherwise 8 feet, 2 inches long.  Brown, cloth-covered, hard wired to the chassis (i.e., no cheater plug).

I am making the replacement 8' 6" but still mulling the idea of a fuse somewhere externally on the chassis (for safety reasons).

The original cord was black and black-with-white-tracer.  

Which is the neutral?  From the schematic, it would appear to be the black-with-white-tracer and that the hot line is routed through the shielded cable (clever, that) to the on-off switch.  True?

And, what did the original plugs look like?

Matthew W. Woodruff

RE: Replacing a Power cord - PhilcoPhan1936 - 12-31-2018

I've always been told to connect the hot lead to the switch side.
Philco used a variety of the round plugs, similar to the link I provided in my earlier comment. I have a 16B here with a brown faceted Bakelite plug like this:

https://vintagewireandsupply.com/antique-replica-bakelite-style-plug-dark-brown/

RE: Replacing a Power cord - rfeenstra - 12-31-2018

I have a few Elmenco fused plugs.  Are these at least similar to what were used back in the day?  Made in the USA.

       

RE: Replacing a Power cord - Ron Ramirez - 12-31-2018

37-116, 37-690, 38-116, and 38-690 used those Elmenco plugs.

RE: Replacing a Power cord - rfeenstra - 12-31-2018

I'll start using these instead of putting a fuse holder under the chassis.  I've got 20 of them!

RE: Replacing a Power cord - jrc0109 - 01-01-2019

What amp rating is recommended for fuse?

RE: Replacing a Power cord - jcassity - 01-01-2019

JRC0109,,
you have to design your answer around your print or device you are working on

your prints normally will tell you in a round about way what amps the unit uses at nominal working conditions.

breakers are sized with the max normal working condition times 1.20.. ie- 10A nominal so 10x1.2 = 12A,, so next reasonable size "UP" is used.

fuses on the other hand are not so easy to calibrate during manufacturing cause its just normally a thin metal strip,, so the industry applies the rule multiplier of 1.5. ie- 10A x 1.5= 15A, so use a 15A.


in radios which i am new to here, ive noticed the prints say a couple things like your volts and your watts.

the formula is power = current x voltage,, so to solve for current, you do........
power divided by voltage = fuse size in amps but remember this is at nominal working conditions.

when the radio is coming up on line, the amps used during that warm up time frame of maybe as high as 10 seconds might reach 160% of the amps you calculate due to what i personally call inrush.... (think motor load coming up to speed but not exactly a good example here as motor loads 30amps in the first 15u/sec can be nearly 200Amps! circuit breakers can be made t absorb and work "with" inrush. ). Fuses cant be made as easily as breakers when it comes to a calibrated amount of amps which the over current protection device will "open". Fuses are treated way different from breakers. Fuses that can work with inrush are usually called "slow blow" and visually have more than just an element within the sight glass.

your line voltage is higher today than what your print may say.. which most say 115vac or 117vac.

if your radio says 150 watts and it says 117vac,, then the math says at that time 1.3amps would be the expected draw.
since you plan a fuse in your circuit,, 1.2 x 1.5 = 1.8amp fuse required,, which means you would use a 2amp fuse.

watts never really changes , its like a constant or the "result of resistance, voltage and current,, what did change for your radio is the voltage. Lets use the 150watt example again but use todays voltage on our outlets.
150watts divided by 124.2vac = 1.207 amps,, and x 1.5 multiplier for a fuse you are at 1.81 amps. you should size to a 2amp fuse here again but.. you may make a choice to use a 1.5amp.

in my Zenith 7h960,, the print says 50watts and my outlets are about 124vac so that means my fuse i pick is really close to 1/2amp.
i installed 3/4A.


all the details above were to benefit anyone who wanted to know how to size the OCP under any normal condition on any device, sorry for the long answer.