good morning, yes it seems to be the DC-injection braking system. don't know about the DC braking... I will check with out it and see! the troublesome relay is 4R on drawing a3-500015. It used to be that this was oscillating and sparking and in turn it was oscillating the LC contactor. I took the co...

Thanks Andy that's very helpful.
The contractors you picture are not the ones I have an issue with. There is another control box under the bed which has a pcb with 4 relays on it ( one of these is the issue), two transformers and two contractors.

Cheers
Bill

Hi Guys thanks for geting back to me.

No, the machine is on 3 phase. I have now taken the control board out. The markings on it are : PC0469 GSM Ltd 1976

Cheers
bill

hi I have recently purchased this 280 synchro. It has developed this issue of the contactor vibrating on and off. I have identified a small relay on the board that seems to control the main contactor in the control box, that seems to be alternating on and off. I have taken its cover off, forced it o...