PLUS 4 Troubleshooting                              Page 3


       5) NO COLOR or BAD COLOR

            A) Check U1  pin 14 for 14.31818 MHz with
               frequency counter.
               O.K.   If not:  1) Check solder joints of CT1
                                  and adjust for correct frequency
                               2) Check crystal, Q1 and Q2
                               3) Check clock circuit for
                                  opens or shorts
            B) Check U1 pin 13 for Color Out signal.
               O.K.   If not:  1) Swap U1 w/known good

            C) Check modulator M1 pin 5 for Color in signal
               is present.
                               1) Check for shorts

       6) NO SOUND or BAD SOUND

            A) Check U1 pin 33 for SND signal
               O.K.   If not:  1) Check socket for open circuit
                               2) Swap U1 w/known good
            B) Check audio circuit for short to ground or loss of
               signal.
               O.K.   If not:  1) Check Q1 - Be sure emitter and base
                                  are not shorted to 5 V.
            C) Check modulator M1 pin 2 for SND signal
                               1) Adjust I.F. can (top right of
                                  modulator) for clean, loud volume
                               2) M1 pin 2 to ground should read
                                  approximately 480 ohms
                               3) Check M1 for components failure


       7) SERIAL FAILURES

            A) Check FB23-26 for shorts to shield or each other
            B) Check U7, U2 and CN2