In order to view the BPM button signal (turns) on the TDS 680B, the scope must be set up to trigger externally, DC coupled, and in 'Peak Detect' mode (from the Acquire menu).

The trigger(s) for the scope(s) is MC00 601(602) (H(L)). The options for these PPDU triggers should be Fiducial Mode: RING, Pulse Mode: SINGLE. The 'Stop Pulse Train' option doesn't seem to matter with these triggers. Ask Stanek if you're wondering what they're for.

The bandwidth for the scope channel should be set at 250MHz, and the channel input coupling should be 50 Ohm, AC (the scope will beep at you complaining about not being able to see below 200kHz--ignore it and press the 'clear menu' button).

10mV is not unreasonable for a first glance at the scope. 1mus/div will show a little over one full turn (1/136kHz=7.5mus). Adjust as appropriate...

Or you can just Recall setup 1.