Help on fault finding on a C3-31 Hammer combination machine

[m_c]

What you might find, is with the braking circuit disconnected, the contactor is still chattering, but as you've not got the braking system cutting in during the chattering, the chattering is not as pronounced or lasting as long.

Although the 3 phase won't give voltages in relation to ground like you'd expect, the measurements between legs should still be very similar to standard 3 phase.

[OMLCNC]

Thank you for suggestions, I will give it another go next week when I'm back in the workshop.

With no motors connected the contactor works fine and the brake (buzzing if stop pressed) so brake cutting in when trying to start motors idea is a strong possibility.

[EddyCurrent]

As far as I can make out, the attached drawing is the coil circuit for the main contactor that is chattering. It may aid in the fault finding process.
The important question is, which components were included in the replacement control box that Felder suipplied ? because the fault is obviously external to that.