My old Dish Network receiver got finally obsoleted so I decided to take it apart and see what we can learn from the design. In the process we discover something unexpected
The motherboard looks rather substantial. A single huge PCB integrates both power and digital circuits. A pretty typical looking AC-DC power supply is on the upper right. It uses all the usual input filters and fuses. Note large plane keepouts around the component leads- that’s to keep high voltage from jumping across. In the upper left corner is a Sat tuner, feeding what looks like an AD9066 60MSps 6 bit ADC. From there pretty much everything is digital. We have an LSI DBS receiver, followed by MPEG2 export and MPEG2 A/V decoder. That in turn feeds a Bt RAMDAC that generates the analog video signals. The video is then even modulated to generate TV output that can go directly into the antenna input. To the left of a modulator is a Rockwell modem- these systems used to dial back to upload purchasing information. But what is that we are seeing under the Smart card socket?!
The case ground connects through metal flaps right to the pads on the board
All that light coming through the board? That seems to tell us that it has no internal power and ground planes and is actually a two layer board. It is rather impressive that such a large design was done with minimum ground fills. Digital buses are going over open air, with no plane under them for convenient return currents.