The problem is I just cannot visualize elctricity, In what form it comes from the wall, what it does in the turntable and how it 'exits'..at the risk of exhausting patience klaus, could you give a quick 'common man' wording of what the electricity is doing when it exits the wall and makes its journey through the 701, in this case?
The same thing vexed me in my studies way back when the earth was flat..
I liked things that can be seen, so I interpreted electricity in a graspable form.
All my studies talked of circuits which were baffling in the beginning so I looked at it differently. Here's some of my mind-aids from antiquity:
a. Water. Sun (Energy) heats up the stuff from a body of water (Source), and it rises up (Hot side) into clouds.
The stuff condenses (dissipates or Works) in the clouds and now falls back (cold or Common side) and returns to body of water. We have a circle or circuit.
b. You sit on your office chair and push (Energy) into the air (Insulator - because the Energy does not have Effect on it..) You're not going anywhere...
Now move chair close to a wall, then sit.
You (Source of Energy) push against the wall with your muscles (Generator). The wall and floor are Conductors of this Energy up to the wheels. The wheels move (Energy dissipation or Work performed- Load).
The Energy flow or circle / circuit GOES from muscle (Energy) via walls/floor (Conductor) up to wheels. Energy is used up (Dissipated) by wheels moving (Work Load). Now Energy's RETURN path or completion of circuit is from the wheels on chair, back to the Source of Energy- You. The Resistance is the friction created in wheels running on the floor. The in-line "Switch" in this energy circuit is your arm....
The circle or circuit is complete.
c. Simple electrics;
Take a small flashlight. Remove battery (Energy Source) and the bulb (Load) out of it.
Run a cable (Conductor) between battery bottom and bulb metal side (or one of the bulb's wires). Touch (simulates Switch) the bottom of bulb (or other bulb wire) to battery top. Light is on /off Depending on "switch",
Light/Load circle/circuit is complete.
Here we have Battery (energy source) containing "muscle" or generator of energy, GOING from bottom of battery up to bulb (Load), then leaving load over other bulb side, RETURNING via Switch - (you intermittent touching) to battery (Source).
Circle / circuit is complete.
You can Alternate this scenario by reversing the battery in this circuit which makes the juice flow backwards, but it will still work the same, because the Energy or Voltage simply changes direction.
In all three cases, Energy only flows when Circuit is complete. The higher level of created Energy, be it muscle or EMF (Electro Motive Force - a ten dollar word for juice...) pushes back against a fixed ground.
Now let's look at Energy route for the juice needed by the 701.
In a simplified way, a large generator (Hydro dam or such) creates Energy at around 760,000 volts and has it GOING to your local transformer sub-station via high tension wires on towers. The RETURN is via earth, back to the Hydro dam / Generator.
This 760,000 volts will push against the zero potential of the earth.
That's the first circle/Circuit.
From the local sub-station , where it is transformed to a lower 3,000 volts or so, it GOES via the top wire (Conductor)on your telephone post to the transformer on your nearest post (or in front of house). That outside transformer also needs to complete its circuit with the local substation and it's done by connecting a RETURN wire into the ground. The earth is the COMMON conductor back to the sub station and the Hydro dam.
That's the second Circuit.
Next, we see a transformer on the telephone pole or at floor level, outside your house. It has the 220 volts GOING into your fuse panel. The heavy ground cable (Conductor) in the fuse panel RETURNS to the transformer again via ground or Earth.
That is a third Circuit.
The fuse panel sends the Hot or GOING Energy from either side of the panel juice, via in-line breakers (Switches) GOING in black conductor wires to the room outlet. The other RETURN or white wire, leads back to the same panel and as you pointed out, via Earth or ground, tying it to that big transformer on the pole (or wherever it sits..) and really to all the COMMON, zero potential earth / ground, including right back to the Hydro Generator.
Initially, we have nothing (no Load) across the AC Socket's GOING/Black wire and RETURNING white wire, therefore nothing happens, because air is a good insulator as we saw. This last Circuit is open.
Plug in the 701 and nothing happens still, if switch is open. One wire of the AC cord goes to the 701's transformer via pin 4 in 701 power box. That line has a fuse which acts as a one-shot-switch for safety. That line/Conductor can be called Common since it isn't switched.
The other wire of the AC cord, ends at pin 2. The 701's paddle switch, when flipped on, goes to pin 3. From pin 3 we go directly into the 110 voltage part of the transformer. Just ignore the 220 volts wire on the transformer...
So, to complete the 701 circuit, we have one side of the transformer on the AC outlet and the other side with a switch in line, on the other side of the outlet. Since we can flip the plug around, we don't care which wire is GOING or RETURNING. As long as the 701 flip switch is closed, power will flow as we saw with the reversal of the flashlight battery.
In order for the 701 to spin records, we see that in this exercise, we passed through three circles of power or Electrical circuits. Each circuit ran on a higher voltage and is transformed to a lower voltage at the end of each circuit, until we finally split the 220 to 110 in our house.
So much for circuits and electrical supply,
In your endeavor to place another switch into the 701, my first suggestion is DON'T.
a. lower the value of the unit if you modify the turntable
b. be at serious risk of shock if the switch and wires are not handled properly.
c. the unit does not need to be on all the time for spin up.
The motor can be kept running if you do not allow the arm to fully return to the rest post. This can be done by blocking the return path over the rest post. There is no damage whatsoever to the slip clutches, if the arm is inhibited from making a full return to rest post. Just slip a pill bottle over the rest post....
Still not satisfactory? OK, for purely intellectual gain and with a warning to take care with wiring and open contacts, you can tap a spst switch such as simple (two screws) wall type light switch, run the two wires and tap them onto pins 2 and 3.
Your drawing already shows one side of your switch onto pin 2, so place the other one on pin 3. I highly recommend you not to do this
because you don't have a noise suppressor on that switch and if any wires are open, the danger from shock can be lethal.
Regards - with Safety Warnings,
Klaus Adlhoch, fmr. Assistant Service Manager,
Noresco -N.Q.I.-Dual of Canada,
Area of expertise: Tech Training and Consumer Service P.R.
Associated with Dual till Thompson era.
Favorite Duals: TG 12a, 1009, 721.