Nice Build but color coding is wrong, right?
Arbitrary, I would say. I used the wire I had.
Nice Build but color coding is wrong, right?
In the post #1,138 where you showed a picture of your build, you are connecting the inlet IEC connector's ground pin (green wire) directly to the screw on the chassis, where you are also connecting from that point to the switcher. That is where you want to isolate the earth ground because you essentially are offering a second return path for current on the IEC connector. For sake of pinpointing where the loop is, try putting a small resistor (10 Ohms or less) or CL-60 between the green wire that goes to the switcher. The basic premise is that you want to insert "a little resistance" between the chassis return paths and earth ground so that the earth ground is only used as an exception due to its (slightly) higher impedance.
It looks like your connector has two wires inside and has a shell shield. First, the outer shield of the connector / cable should only be connected at the source end (the chassis with the switcher inside) otherwise you will have TWO current return paths from the destination device, and likely a ground loop. This is similar to why you isolate the earth ground as I said above. Next, test continuity between the pins on your output connectors and the chassis the star ground point - you should not have any continuity between these points. You should only see continuity between the output cable's outer shield and chassis.
If you don't know how to do this, put your DVM in "ohms" mode and most have an audible beep/tone option. Connect your negative lead to the star ground and then use the positive lead to probe and connect each of the pins on the IO connectors and shield. If you touch the chassis anywhere you should get a beep and show continuity with the shield and all other parts of the chassis including the heat sink of the switcher. You should not see continuity between the star ground point and the pins on the I/O connectors.
--Tom
You might have some induced noise. Definitely compare with the Sigma to rule out the switcher. Try another switcher also for reference too. Looking at your pictures, I wonder if its the switcher's transformer. I just noticed from your picture that its an open frame design so that could be radiating next door to the filter board and so on. Also try twisting your wires together as well as adjusting their spacing near other cables / the transformer. In the end, it might just be the switcher which might have been designed to be put into its own shielded container or the applications it was designed for didn't worry too much about induced RF/etc...