John, On 12/20/2015 06:31 AM, John Thornton wrote: > I'll start with a couple of photos of the el cabinets before breakfast > and get more details after. > > http://gnipsel.com/images/bp-knee-mill/bpel01.jpg > http://gnipsel.com/images/bp-knee-mill/bpel02.jpg > > JT >
We used to have cabinet grounding problems on PDP-11 series until we connected ground wires from each cabinet, doors, and computer chassis to one point in the power entry cabinet. Wires were thick, over 2mm or so if I remember correctly. As Gene and others have pointed out, star configuration is the only way to go. As far as I can see from your pictures (bpel01.jpg right top corner for example), you seem to have more than one ground connection in the box. That seem OK logically but it's not good for a number of reasons, resistance, ground loops, RF. Box is not a GND star center. Metal brackets don't seem to be grounded to one point either but they have circuit boards with spacers on them. You can get a copper grounding bar with holes and screws in hardware store to create a large ground post for everything in the box. Outside ground from power cable needs to be attached to it first then other things including box, the door, and shielded wires between the electronic devices. Don't forget the fans. Since this is a retrofit (?) I would remove all ground wires, check for corrosion or electrolytic effects, and connect them to one ground. Note that a mix of steel washers and copper wires has it's own issues. In addition, I would turn all screws on boards back and forth to make better connections also. Next thing is PSU. Old electrolytic caps may not be good enough anymore, there might be RF noise problem between the circuits, wires too thin to carry the current, etc. -- Rafael ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
