[R-390] R 390A Line Filter Trial

[Charles Steinmetz]

Barry wrote:

>At one time, I made several adapter plates for the CorCom 
>filters.  *     *     *   CNC plasma cutter that helped get all the 
>holes in place such that the CorCom's face lined up with the 
>existing hole (which is kind of critical since the IEC plugs are 
>just small enough to fit inside the existing hole)

Having the removable IEC cord is handy, but if that isn't an absolute 
necessity the filter modules are available as "lumps" with solder 
terminals, much like the originals.  I don't know if any currently 
available filters have mounting holes that exactly match the 
originals, but in any case some owners may find that style is much 
easier to mount than a complete IEC entry module.

Having said that, I have found that 390s and 390As work absolutely 
fine with no line filter at all.  Perhaps if one is installed in a 
welding shop or other industrial facility with lots of immediately 
local noise on the power line it might help reduce the conducted RF, 
but in that case the radiated RF would be a much worse problem than 
the conducted RF anyway.  So, feel free to just pull the filter out 
-- you won't ever notice it's gone (except that it won't trip your 
GFI anymore).  DO retain the chassis ground wire and 3-prong plug, 
and DO make sure the outlet it is plugged into is properly grounded.

Best regards,

Charles