Do you mean you have a Dish 500 satellite dish with a Dish Pro Plus Twin LNB mounted on the dish? In theory a 3700 will work with a Dish Pro Plus LNB but reality may be different. The power supply in a 3700 was not designed to run a DPP LNB and the electrical demand may exceed the capabilities of the 3700. The DPP should be used with a Dish Pro receiver and a LEGACY (3700) receiver as the second receiver on the system.