Strong SRT8500 Service Manual page 17

3) Weak TUNER signal
Check first that the voltage is impressed to LNB. If there is nothing wrong in LNB
Voltage, check if the voltage is impressed well into TUNER bundle and if data flow
out properly. If every condition is satisfied, TUNER itself can be considered to be
defective. In occasion, precise inspection should be done in case that there is
SHORT between pins(fault rarely made by a worker).