[Bryan Rogers]

I,m working on a Sharnoa SVC 36 Mill and when I push the momentary ON button on the control the contactors pull in and the power supply and drives come on but as soon as I let it out the button the main contactor pulls out and the timer relay stays on for about 1 sec and then the contactor for the P/S pulls out. As long as I keep the start button pressed it will stay on. Possible relay problem or aux contactor issues???? I don't have any wiring diagrams for this Mill and Sharnoa is out of Business in the states. Any help would be great. Probably a simple fix
Also the Power supply is getting extremely hot when the mach. runs. Don't know if these are related problems

[123CNC]

Don't know the specifics of your machine, but it sounds as though your momentary push button and power supplies and contactor coils are all in working order, but you are missing the latched power to the coils. This may be passed by a separate relay or not unusual to be wired through a set of NC contacts on the relay or contactor in question. The hold or latch power will likely be wired through a normally closed OFF switch which would drop power when pressed and unlatch your relays/contactors. If so, check, i.e. visually trace the related coil power wiring to see where the latch circuit is coming from, and double check your off button for a good N/C contact and wiring. See if there are any separate fuses on the 'off' circuit and if so verify OK.

Your hot power supplies shouldn't be a problem, unless you are also blowing fuses. But you may want to double check and clean any vents or filters and make sure any enclosure fans are still operational.

[Bryan Rogers]

Thanks, I'll check the contactor in question since there is no off button on the control. Only an E stop, then the main disconnect. We normally hit the E stop button and then just hit the on button when we power up. I think its a small relay or latch poewr on the main contactor feeding the PS contactor.

[rkbcnc]

I had the same problem. Just replace the main power contactor.