SONY TRINITRON – KV-1985MTJ

     Auto search tuning does not lock at all.  Indefinite auto searh. Auto tuning dose not stops or lock any stations in memory.

     Check the AFT signal at pin number [35] of IC 001 (M34302MB-612SP). Signal voltage to this pin comes from TUNER/VIF module (IF201 – IFD-380A).  Check the voltage at output pin number (6) of this IF module first.  If no voltage is there, check C202 (0.47uF) capacitor for leak.  If this capacitor has leak, it will short out the AFT voltage to ground, as it is connected to ground.  Replace it.  It will be best. Check R205 (33K) connected to positive 9V supply rail and AFT pin of the Tuner VIF pack for open.  If found defective, replace the resistor. Check C003 (0.001uF) ceramic disc capacitor soldered very close to pin number [35] of IC001 for leak. These are the only three external components to be checked for this fault.  If all of these are found OK, and still there is no voltage from AFT output pin from the Tuner VIF pack, make sure that the pack itself is faulty, and should be replaced with same type and number. 

     If AFT voltage is there, and still no tuning lock occur, check the voltage at pin number [36] of IC001.  It is the sync: voltage from LOT.  Must show about (0.7) volt.  If this voltage is not there, check (R029 – 33K) for open.  If this resistor is found OK, and still there is no tuning lock, make sure that (IC001-M34302MB-612SP – System Control Microprocessor) is defective.  Since there is no external memory chip is with this set, and the system memory is built inside the main system control IC, no more check must be done.