TB 9-6625-2139-24
(5) Position controls as listed in (a) through (c) below:
(a) VERTICAL MODE TRIGGER SOURCE CH 1 pushbutton to in position
(AN/ USM-488).
(b) VERTICAL MODE TRIGGER SOURCE CH 2 pushbutton to out position
(AN/ USM-488).
(c) A TRIGGER A&B INT switch to CH 1 (type 2235).
(6) Adjust R309 TRIGGER OFFSET (fig. 2) for multimeter indication recorded in
(4) above.
(7) Position controls as listed in (a) through (c) below:
(a) VERTICAL MODE TRIGGER SOURCE CH 1 pushbutton to out position
(AN/USM-488).
(b) VERTICAL MODE TRIGGER SOURCE CH 2 pushbutton to in position
(AN/USM-488).
(c) A TRIGGER A&B INT switch to CH 2 (type 2235).
(8) Repeat (4) through (7) above until multimeter indications in (4) and (6) above
are equal within 1 mV dc.
(9) Disconnect multimeter.
(10) Position controls as listed in (a) through (g) below:
(a) VERTICAL MODE CH 1 BOTH CH 2 switch to CH 1.
(b) VERTICAL MODE TRIGGER SOURCE CH 1 pushbutton to in position
(AN/USM-488).
(c) VERTICAL MODE TRIGGER SOURCE CH 2 pushbutton to out position
(AN/USM-488).
(d) CH 1 VOLTS/DIV switch to .1.
(e) CH 1 AND CH 2 AC GND DC switches to AC.
(f) A AND B SEC/DIV switches to 10 Ps.
(g) A TRIGGER A&B INT switch to CH 1 (type 2235).
(11) Connect oscilloscope calibrator CHAN 1 to TI CH 1 using a 50 :
feedthrough termination.
(12) Set oscilloscope calibrator LEVEL SINE output to 50 kHz and 2.2 divisions of
vertical display on TI.
(13) Set CH 1 VOLTS/DIV switch to 1.
(14) Adjust R479 A TRIGGER INSITIVITY (fig. 2) while rotating A TRIGGER
LEVEL control slowly so that the A trigger is just able to be maintained. (R)
(15) Set CH 1 VOLTS/DIV switch to 50m and adjust A TRIGGER LEVEL control
fully cw.
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