TB 11-6626-620-35-2
(19) Depress Test Instrument RESET switch.
4-1. Distortion Measurement Check. a. Per-
(20) PERCENT DISTORTION meter shall in-
formance Check.
dicate 0.
(1) Slowly adjust the pattern generator %
(21) Set Test Instrument POLARITY switch to -.
DISTORT control from O to 50.
(22) PERCENT DISTORTION meter will in-
NOTE
dicate beyond 25%.
The % DISTORT control must be moved
(23) Depress Test Instrument RESET switch.
slowly so that the meter pointer will not
(24) PERCENT DISTORTION meter will in-
jump to off scale. If the meter pointer
dicate 25%.
jumps to off scale, press the RESET button
(25) Make the Test Instrument and pattern
and repeat the % DISTORT control ad-
generator switch settings shown in table 4-1, and in-
justment.
dications shall be as indicated therein.
(2) The Test Instrument SIGNAL lamp shall
Table
4-1.
Distortion
Measurements
flicker, LATE lamp will light and PERCENT
Test Instrument
DISTORTION meter indicator shall follow control O
Pattern generator
Indication
to 50.
RATE switch
PERCENT DISTORTION
RATE switch
(3) The indication on the PERCENT DISTOR-
(bauds)
(bauds)
meter (%)
TION meter shall move from 0 to 49.2% distortion in
63 increments (this is derived from a binary count cir-
7.5/45.5 . . . . .
*24 t0 26
45.5 . . . . . .
7.5/50 . . . . . . .
24 to %
50 . . . . . . . .
cuit).
7.5/74.2 . . . . .
74.2 . . . . . .
24 to 26
(4) Set the Test Instrument DISTORTION
7.0/150 . . . . . .
150 . . . . . . .
20 to 25
SELECT switch to MARK/SPACE.
(5) Depress Test Instrument RESET switch.
* Depress Test Instrument RESET switch to obtain each
(6) PERCENT DISTORTION meter indicator
shall drop to 0.
indication.
(7) Set the pattern generator DISTORT SELECT
b. Adjustments.
switch to BIAS MARK and % DISTORT control to O.
(1) With power cord disconnected, remove Test
(8) Set the Test Instrument DISTORTION
Instrument from case.
SELECT switch to SPACE/MARK.
(2) Remove (12) screws from top panel of the Test
(9) Slowly adjust the pattern generator %
Instrument.
DISTORT control from 0 to 50.
(3) Remove card 1A2A15 from the Test In-
(10) Test Instrument EARLY lamp light and
strument. Remove extender card 1A2A7 from dummy
PERCENT DISTORTION meter indicator shall
socket and insert into 1A2A15 socket.
follow control 0 to 50.
(4) Insert card 1A2A15 into the extender card
(11) Depress Test Instrument RESET switch.
1A2A7.
(12) PERCENT DISTORTION meter indicator
(5) Set RATE switch to 75.
shall drop to 0.
(6) Set CURRENT SELECT switch to 20).
(13) Return the pattern generator to the same
(7) Set FILTER to OUT.
positions as indicated in paragraph 3-3 above.
(8) Set DISTORTION SELECT switch to PEAK
(14) Set the Test Instrument DISTORTION
TOTAL.
SELECT switch to PEAK TOTAL.
(9) Connect the Test Instrument to an AC power
(15) Slowly increase the pattern generator %
source.
DISTORT control from 0 to 40% and then return to
(10) Do not apply an input signal.
20% .
(11) Turn POWER switch to ON.
(16) The Test Instrument PERCENT DISTOR-
(12) Depress the Test Instrument RESET switch.
TION meter indicator shall follow control to 40% and
(13) Connect a lead momentarily between the
remain there until the Test Instrument RESET
chassis and base (2 contact printed circuit board con-
switch is depressed.
nectors) of transistor Q6 on card 1A2A15.
(17) Set the pattern generator % DISTORT con-
(14) Adjust R15 of card 1A2A15 for a 25 percent
trol to 25%.
indication on the PERCENT DISTORTION meter
(18) Set the Test Instrument POLARITY switch
(fig. 4-l). (R)
to +.
