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First unplug the rec. Then remove the cover. With the rec facing you look in the lower left hand corner. There will be the power supply. Try to id the the 7818 voltage reg. This is readily available from any elec. supply. Will cross to a NTE958
Check the small zenor diode that is tied to the IF switch. It is located in the back right corner and is soldered between the 18v point and ground.
Check the coil. It is located about 2 inches from the diode along the right edge of the board.
Check the circuit breaker for the 18 volts.
VR1 7805 regulator
U11(LM7001) and Y1(4.000Mhz Xtal)
Check and replace C4 220 mfd/16v, C5 4.7 mfd/25v and C8 220 mfd 10v on microprocessor board.
Replace U610 (TC 9153) on main board.
Check for shorted surge suppressor diodes at rear of main board.
Check and replace U24 TC9154
Check for a open R39 1 ohm 10 watt on relay board
Check and replace U21, GA-01D surface mount IC.
Replace IC U20 MB88303
Replace U1 on tuner board LM317T
Check for a shorted Q5 or Q7 both are IRFZ20 mosfets
Check for a shorted Q4 or Q6 both are IRFZ20 mosfets
Check connectors on grounding block, LNB, and back of receiver. If good, check alignment. If needed, move dish to see if you might have a "dead spot" (magnetic anomaly caused by mineral and enviromental conditions which interferes with RF signals)
Replace LNB. On rare occasions, the receiver may have to be replaced if the unit suffered a lightning/surge hit. If the unit is not grounded, the microprocessor can be damaged.
Replace +5v Regulator (LM7805) on power supply
Replace Q501 (ECG-85) on main board
Change all caps in power supply, verify regulator IC's
Replace cap C113. location demodalator board located behind tuner
Replace C809 and C810 on the front power supply. One is a 10uf and the other is a 33 uf electrolytic capacitor. Remove the front panel and you can unsolder both without removing the power supply. Their identifiers are etched on the back of the power supply. Use a pair of tweezers to remove. Pay attention to polarity in replacing caps. One has the negative to the left (as you look at it). The other has the negative to the top.
Most likely tickled by lightning. First, replace the four general purpose diodes (1N4148) and the three (or four depending on model) transistors on the back edge of the actuator power supply. It is mounted on the left edge of the receiver. Then, look for a burnt off PC run on the back of the power supply. It is a fused run and is intended to pop off under lightning conditions. Repair run and test.
If the units PC run is intact, then it is possible that you have a cold sold joint on the large transformer. You will have to check voltages at the output of the transformer and compare it to the opposite end of the pc run for that contact. It is a common problem for the transformer, because of the installation, to break loose. Resolder and check.
Locate the grey, two-wire, connector on the front power supply. Look for 18volts on one of the connections. If it is present, then the EPROM is bad. Replace the 80 with a 611G and the 100,120 with a 602G version. If the 100 is an older version (no Baseband output on back of receiver) then it needs a 601D version.
Replace Q406 and Q405 on act power supply location <front of receiver>
Check relay on RF board (follow the "C" AND "KU" rf input connectors from the back panel to this board). If you tap on it and the signal returns. . . that's your problem! You can either replace the relay or just flip back and forth between C and KU 20-30 times. The relay contacts will clean themselves this way.