If anyone else ends up in the same boat as me with a heap of SCT013 15/30/50 that return a voltage instead of a milliamp reading - then it is a ridiculously easy fix to remove both (the 15amp units only seem to have one) burden resistors and takes no more than 2 to 3 minutes per unit.
Make sure you have a soldering iron with a nice sharp tip and a pair of helpng hands makes everythign go much more easily.
- From the bottom push the cable up into the housing a couple of centimeters.
- Open the clamp - looking from the top you will see two small blue tabs - this is all that holds the PCB and split magnet unit in the housing
- I have found the easiest way is to slide a small jewellers screw driver down between the housing and the PCB and just slightly angle the PCB forward and away from the tabs
- If you have pushed enough cable through from the bottom this will provide enough upward force to move the PCB out from under the restraining tabs
- SLowly feed more cable in and the unit will come loose from the housing.
- on the PCB you can see the two resistors (they are tiny surface mount units)
- Place the PCB in your helping hands clamp and hold the sharp point of your heated soldering iron agains one side of the solder on the SMD resistor and apply a gentle force with the tip of the soldering iron pushing the resistor towards the other side - as the solder melts the resistor will come free of the PCB and bend upwards - you can then push it bakwards and the legs on the remaining side will snap free.
- once you have both of these resistors free thats it - slide the unit back together until the PCB is resting under the two restraining tabs again.
Here is a reference for this - this shows a picture of one with the two resistors removed
These appear to track exactly the same as the SCT013-00 (100 amp) unit and to very closely align with an external Killawatt meter