Hi,
thanks for the idea, Thorsten.
I easily found the program itself (deep_scan.dsk) and an emulator (SimCoupe.exe).

Loading the disk into drive 1 autostarts the chess program; yet it looks like only two commands are valid (apart from moves input): new (for a new game) and stop (to quit the program).
There is no direct input to change the default thinking time (180 secs).

The way I succeeded:
- stop to exit the program
- input: 15 LET time=x
-----> where x is the wanted thinking time in seconds
- run

This inserts a new basic line that overwrites the time value previously set in line 10:
As a lazy guy, I find easier and quicker to insert the short line 15 rather than deal with the long 10 one.

Hope this helps,
Eric