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Is this usual in Philco sets?
#1
Hi.

I am in the uk and restoring a Philco , the attached images show the circuit diagram and part of the under chassis around the 35Z4GT.

In addition to the Live and Neutral there is a separate mains Earth all emanating from a modern 13 Amp plug.

The Earth wire is soldered to what looks like pin 6 which I think is not used and then via a capacitor to the chassis.

This is not shown in the circuit diagram. 

We have been talking about this on our UK Vintage Radio forum but I would appreciate comments from the Philco experts here!

Thank you.


Attached Files Image(s)
       
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#2
I am not sure the Earth ever got used like this, after all the outlets simply did not have it back in those times, but using unused pins on the tubes, specifically in rectifiers (and in others sometimes too) as solder posts is usual practice with Philco, and I believe, with others also.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
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#3
many times unused pins on sockets are used as a means to continue a component to wire transition or to chassis.
the prints never show this level of detail, you have to just know that its the same path electrically no matter if a terminal is used or not.
generally terminal strips are not shown either.

looking at the pic and the diagram, not sure why you have the N & hot AC power leg across the on/off switch. the breaker you power from should be tripping.
~gets me thinking maybe someone retrofitted in a safer plug design sometime in the past.

normally the ac power leg will come in to the on/off sw then power continues out of the on off sw then out to the radio components.

"I" personaly would bend pin 7 inboard a tad, too close to the chassis.
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#4
Hi and Welcome!
Always like having a look at the UK models vs are US sets.
Typically the US sets wouldn't have B- connected directly to the chassis it would be floating and have a cap between the chassis to B-. Your set is the other way around.
I would remove the earth wire as it does make for the possibility of a shock hazard from ac leakage thru the capacitor depending on which way the plug is connected to the mains. With that being said using the neutral as the rf ground is a bit noisier than using a separate earth ground (separate from the mains). Now days the mains are full up with all kinds of rf trash from switcher power supplies and microprocessor controlled devises. The further you can get the rf ground away from the mains the better/quieter it will play.
In most cases the US models are pretty different from the UK built sets. I think the US set would be this one the 48-464. Outside looks the same but under the hood it's way different.

http://philcoradio.com/gallery2/1948a/#Model_48-464
http://www.nostalgiaair.org/Resources/636/M0013636.htm

GL
"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow

Terry
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#5
Back in the day mains power could be very different than what we have today.  In the USA having 120 volt 60 hz was not everywhere in the country until 1980+or-. Growing up in Tampa I can recall my dad having trouble with the fuse box, if a fuse blew and you measured from the neutral to a ground got 60 volts!! Both wires had a fuse what we today would call hot an neutral. My dad had someone come out to look things over and he would have the panel changed but the power company had to install a new transformer on the pole. the old transformer was 120 volts only and each side of the plug was hot. If you measured either side to ground got 60 volts AC. The other houses on the block were still on the old transformer the last ones were changed my senior year in High School  1967. In 2010 was visting friends in OZ went to Philip Island for a stay at there summer house and was asked to look at the wiring what I found was both wires were hot 230 volts 50 Hz.  each side to ground was 115 volts 50Hz. House was built in 1947 no grounds in the outlets. There was a old tube radio at the house that was his aunts from when she lived in the house I did restore the radio for my friends and both wires were switched It was a Phillips. In 2017 I was gifted a signal corp generator made in 1954 model PE-75-AF was able to get the gas engine running  and the thing makes power has a 2 prone twist lock plug no ground. the TM states you run a ground wire from the gen set to your radio equipment. measuring from  either blade to ground is 60 volts blade to blade is 120 volts. Was able to find info on radio equipment used by the signal corp during this time frame and both wires are switched. Sorry about the long post
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