Hi Eugen,
I use a Revox C270 on a daily basis for digitizing and archiving work, and periodically do a quick playback alignment using the appropriate MRL Reproducer Calibration Tapes. As you probably know if you have the Studer Revox service manual for the C270, all of those adjustments, as well as the record adjustments, can be done without an extender board and cables. In my understanding, those items are only necessary for serious troubleshooting, and working on circuit boards that are not part of the routine alignment and maintenance.
I don't have the extender board and cables, and I'm afraid that I don't know anyone who does, other than the Studer/Revox person who does my service work, Jack Clark, at JM Technical Arts, in Nashville, Tennessee. What are you trying to adjust on your C270?