The old part timer has installed several DPP44's and always used the power unit provided. The other day I was servicing a site that had a 500 and a 300 running into a 44 but the 44 did not have external power. The switch was feeding 4 receivers, some of them dual and everything was working fine after some reallignment. Especially with the issues of burned out LNB's we have read about, when do you need to use a power supply???