SD-DVR80 channel problem

Our old Tivo box is acting up (I think DVR-80s use dog years so ours is

really old). If you watch the signal strength the satellite 1 input is normal

and stable. The satellite 2 input (on about 6 of the 32 transponders) is

cycling on and off. We've done enough troubleshooting to prove it is

inside the DVR-80. I do have some spare parts but I need to know which

circuit area is the probable cause and if someone knows where we can

find a diagram for the box.



Thanks

john and curly