cCWN76:83
                                       
                PRODUCT DeTECTOR AND BALANCED MODULATOR SWITCHING INPUTS:
                       Examine IC8 pins 5,6,8 and 9 for 1 kHz symmetrical
                                                             squarewaves.
            If this fails, examine pins 3 and 11 for a a kHz pulse input.
           Repeat for IC9, looking for 500 Hz squarewaves and 2 kHz input
                                                                  pulses.
                                                                         
             This completes tests on tho time base portion of the filter.
                Now perform step 1 of the TEST SPECIFICATION. If the test
                   succeeds continue with the test specs. If it does not,
                                                                 continue
                                                                   below.
                                                                         
            SIGNAL PROCESSOR BALANCE: With the filter set up according to
           Test Spec. step 1, main the following measurements with a d.c.
                                                               voltmeter:
                                       TP6 and TP7: less than 1 millivolt
                                                       + or -  to ground.
                        (investigate short circuits or faulty IC10, ICll)
                                TP8 and TP9: less than 1 millivolt (ICll)
             TP10 and TPll: less than 5 millivolts. If this is OK, set S2
                                                                       to
             1 bit/sec. The reading must stay less than 5 millivolts, but
              it will not be constant. If this test fails, it is probably
               due to leaky 1 uF capacitors C4 and C6, faulty IC12, Ic13,
                               Ic14, or solder flux on the circuit board.
                TP12, TP13: less than 100 millivolts with S2 in 1 bit/sec
                                                                position.
                If this fails check leaky C8 or C9, faulty IC15 or 16, or
                                                    solder flux on board.
            TP14, TP15: less than 100 millivolts as above. Check IC17 and
                                                     associated circuits.
                                                                         
           When all these tests succeed, repeat TEST SPECIFICATION step 1
                                         and continue with the teat spec.
                                                                         
          5. Continue OF SIGNAL PROCESSOR PATH: If Test Spec Step 2 fails
            to produce audio output, make the following a.c. measurements
           with the scope using a 10 mV synthesized audio input of 1000.0
                                                                      Hz.
                                          TP6, TP7: 50 millivolts, pk-pk.
                                         TP8, TP9: 50 millivolt irregular