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

[OMLCNC]

1. reconnect C1 and try to start the motors again, do this 3 times, once for each motor.

2. reconnect SP (leave C1 still connected) push in one of the E/Stop buttons, switch to saw and try to start the motor.
You should hear the motor humming as the brake applies DC. If that works okay it suggests the brake unit is working.
Repeat that 3 times, once for each motor.

3. one thing I don't like is this; when you press the start button (contact 23/24), it applies voltage to SP and for the time it takes the contactor to pull in there is also a circuit via C1 (R7/R8)
On a sample diagram from the Klinger Born website I linked to earlier, it shows the start button having a normally closed that open circuits the C1 circuit when pressed, this makes more sense especially
if it's a 'break before make' type.
It may just be that we don't fully understand the brake unit's operation.

So carried out step 1 and 2.

Yes the brake works but the chattering has returned, no logical pattern, it can hapen in any position of the rotary switch.
First start can be fine and second and third then fourth chattering, rotate switch starts fine, second chattering...... etc.... so no logic.

Will now look at rotary switch.