4-9
IFB A
1 Move the J4 jumper to short pins 1 and 2 (IFB A assigned to channel 3).
2 Remove the signal from PROGRAM B input, and connect it to the PROGRAM A input. Set
the signal generator to 0 dBu, 1 kHz.
3 Check the output level across intercom channel 3. It should be –9.8 dBu ±2 dBu.
4 Turn on the CH 3 TALK and MIC ON buttons. The channel 3 output should drop at least 45
dB from the reference level in step 3.
5 Turn off the CH 3 TALK and MIC ON buttons.
6 Ground the Key 3 input (short J22 pin 7 to pin 10). The channel 3 output should drop at least
45 dB from the reference level in step 3.
7 Remove the Key 3 ground.
8 Move the J4 jumper to short pins 2 and 3.
Level and Frequency Response Check, Four-Wire Input to
Headphone
Four-Wire A Input to Left Headphone
1 Set all front panel buttons to off. Set all volume controls to minimum.
2 Remove the signal generator from the Program A input, and connect it to the Four-Wire A
input (AUXILIARY connector J22, pins 8 and 21). Set the generator to 0 dBu, 1 kHz.
3 Move jumper J19 to short pins 3 & 4 (Four-Wire A input always on).
4 Set the CH 1-3 volume control to measure 0 dBu at the left headphone output. (The control
should be at about the 2 o’clock position.)
5 Set the signal generator to 0 dBu, 100 Hz. The left headphone output should be –0.9 dBu ±2
dBu.
6 Set the signal generator to 0 dBu, 10 kHz. The left headphone output should be –4.7 dBu ±2
dBu.
7 Move jumper J19 to short pins 2 & 3 (Four-Wire A input off).
Four-Wire B input to Right Headphone
1 Remove the signal from the Four-Wire A input, and connect it to the Four-Wire B input (J22,
pins 9 & 22).
2 Move jumper J20 to short pins 3 & 4 (Four-Wire B input always on).
3 Set the CH 2-4 volume control to measure 0 dBu at the right headphone output. (The control
should be at about the 2 o’clock position.)
4 Set the signal generator to 0 dBu, 100 Hz. The right headphone output should be –0.9 dBu ±2
dBu.
5 Set the signal generator to 0 dBu, 10 kHz. The right headphone output should be –4.7 dBu ±2
dBu.
6 Move jumper J20 to short pins 2 &3 (Four-Wire B input off).
