How to Capture a TSL 100

I have a TSL 100. It has a clean effects loop and a second fx loop for crunch/lead

I can capture the clean fine, but If I unplug from the return of the clean fx loop the FX loop for both channels disengages unless there is something plugged in the send of fx loop 2 but then theres nothing running to the send so the signal dies. How do you capture the second and 3rd channel of this amp? Anyone own one?

According to Marshall: Two parallel effects loops, each with its own Mix control. If only Loop A is used, it acts as a master loop. If only Loop B is used, it acts as a loop for Crunch/Lead. If both are used A is for Clean, while B is for Crunch/Lead. That being said, isn’t this a 3 channel amp? Why do you need to use the FX loop to change channels?