Older UM70's did not have any rf traps on the outputs, they forgot to add them. You can add them without adding large aftermarket pigtails.
Solder a pair of .022 uf caps from pin 2 and 3 to pin 1 on the internal XLR connector. Keep the leads short as they can rectify rf via lead inductance. To eliminate that use a pair of .022 uf mono ceramic surface mount caps and solder them to the XLR connector.