Tek MDO4000 calibration procedure?

[Howardlong]

Could anyone point me to the scope calibration procedure for these scopes please? Although it's script driven form the UI, there is a step close to the end (of course!!!) that I can't get to pass although as far as the brief onscreen narrative describes, I believe I'm giving it the right signals.

If it makes any difference, it's an MDO4104C-SA6. The spectrum analyser section is fine, it's the scope calibration procedure I'm after, so it's possible a DPO/MSO4000(B) procedure would also help identify what I'm doing wrong. Edit: looks like the DPO/MSO4000(B) calibration procedure is in its service manual unlike the MDO4000.

Edit: FWIW, it's step 76 that fails (of 78) which requires a 1Vpp 1kHz 50 ohm on all channels for deskew, the same as step 73, which succeeds.