Today I modified the HEQ5 Pro mount with the “Rowan belt modification”

This kit replaces the factory spur gear drive train with timing belts.
The pulley modification reduces the spur gear errors that are typical and
therefore reduces tracking errors. The belts also make slewing much quiter
eliminating the ‘grinding’ noise that the standard spur gears produce.

It’s was a little bit fiddling but with the help of some great YouTube-tutorials I managed without difficulty.

My PHD2 guiding improved massively. The specific 13.6s periodical error the mount had before, is more or less gone now.