Hi Sensor,
If you could take a good sharp photo of your SK-1 circuit board (both sides) and post them up here or email them to me I could probably pinpoint them for you.
One dead giveaway as to the CV envelope lines is the 4 little diodes on the board, near the processing chip. See the photo below. This is for the SK-8, so it won't be the same on your board. But look at the diodes - these WILL be the same on your board, and these are what you are looking for. Hook up your CV tap wires to the ends of these diodes somewhere convenient. You can verify them to be the CV points by putting a + multimeter probe on the diode leg, and the - probe on the - battery terminal spring. Set the multimeter to DC volts. Switch your SK on and play a 4-note chord and hold the notes. The meter should read about +2.5V DC. Release the notes and it should drop down to zero or close to it. These confirm it is a CV point. Do it for the other 3 diodes to confirm that they also show this, and then they are your 4 CV points, one for each voice of the 4-note polyphony.
You'll notice in my pic that my CV wires are off wire jumpers or resistors - this is because they were directly after the diodes, and were an easy soldering point. But you might want to solder them from the circuit track side of the board instead, and so can solder them directly to the track legs of the diodes if that suits you.
Hope that helps,
Cheers, graham