nozza87 thanks for the reply, should make setting up a whole lot easier. One final question, why is it necessary to include the 500 ohm trim pot set 110 ohm difference between the black and yellow wires, if this difference is already present pre-mod?
I admit I haven't looked inside my Tx yet, and the answer may be obvious when I do, but it seems that even when the mod is switched out, you have introduced an additional 110 ohms in to the feed on the black wire.
The balancing of the stock pot is required and I'll do my best to explain why:
The yaw can only be calibrated at stock values to allow for full range control (-1000 to 1000)
If you add resistance to values that have a different midpoint you will end up with two values that become more and more apart the more resistance you add because of the resolution of the pot and the way the software calibrates it.
As far as i understand the assistant software 'calibrates' the yaw by looking at it's left resolution (range) and dividing it by 1000 giving it it's incremental value.
It then does the same for the right resolution (range).
It does not matter that the left resolution may be 1.63 kOhms and the right is 1.49 kOhms because they both are calibrated to increment towards 1000 by the same percentage of their respective resolutions.
E.g: Left incremental value = 0.00163 (1.63 / 1000), Right incremental value = 0.00149 (1.49 / 1000)
If you push the stick left 50% you will get 0.815 kOhms which divided by 0.00163 = 500 (50% of 1000)
If you push the stick right 50% you will get 0.745 kOhms which divided by 0.00149 = 500 (50% of 1000)
Even thought the actual resistance values are different you still get 500 when at 50% due to the calibrated incremental value.
(for the next bit i am excluding how resistors actually work and just using basic math to show the problem so the value may not be correct but they are proportionate to the actual values)
Now if we left the pot at these stock mismatched values and added 100 Ohm resistance equally to both sides, we get:
stick left 50% = 0.815 kOhms - 100 Ohms = 0.715 which divided by 0.00163 = 438.65 (44% of 1000)
stick right 50% = 0.745 kOhms - 100 Ohms = 0.645 which divided by 0.00149 = 432.86 (43% of 1000)
In this example there is only a 1% difference but that is a difference and in reality it is much higher meaning left yaw will be faster than right yaw which for most is undesirable.
Now you might be thinking you could just adjust the two 20k trimpots individually to allow for the difference balancing out the left and right but this will not work due to the difference being a multiple of the resolution which changes at every increment towards 1000 exponentially.
So while there is a 1% difference at 50% there may be a 1.8% difference at 20% which is nearly double the difference meaning you would need a different resistance depending on the position of the yaw pot.
But if you balance the initial values of the yaw pot you do lose resolution on one side but it matches the resolution of the other side making their incremental values identical so when you add resistance it is also equal on both sides no matter what the position of the yaw pot.
Clear as mud? I hope this explains it or at least helps,
Please note: I understand there may be errors in my math but this does not matter, what matters is the basic principles of how and why this works and doesn't work which i have done my best at explaining.