AT&T Bell System Plant Series Alignment Instructions page 11

SECTION 107-302-500
lamp states are obtai:p.able, the supervisory bias
can be measured, adjusting if necessary, and end
the routine maintenance or verification. If these
lamp states are not obtainable, adjust the super-
visory bias and again attempt to obtain the lamp
states. If bias cannot be adjusted, sectionalize
trouble to the supervisory demodulator. If the
bias can be adjusted but the desired lamp states
are unobtainable, sectionalize trouble to the super-
visory demultiplexer. The bias adjustment of the
supervisory demodulator (screwdriver adjusted
potentiometer on CP63) is accomplished as fol-
lows. Under the conditions resulting in a demodu-
lated 95.5-bps dotting signal, connect the super-
visory demodulator output to the distortion meas-
uring circuit by operating relay SSC. SSC is
operated when CRD and SV are operated in the
20A; these were operated when SMC was pre-
viously operated. Operated relay BD by operating
the DMS BIAS key; this will condition the distor-
tion measuring circuit to measure supervisory
bias. Adjust the BIAS potentiometer while oper-
ating the BIAS key on the display panel alter-
nately between MK and SPC. Equal minimum
readings in both key positions of less than 5 per
cent will be the zero bias point.
C. Distortion Check
4.34
Verification That Distortion is Less Than
8
Per Cent for the 906A Generated Super-
visory Dotting Signal: Operate the DMS SUPV
key. This will cause the BD relay to be released
and the PS relay to operate, which will condition
the distortion measuring circuit to measure the
distortion. The distortion as read on the meter
should not exceed 8 per cent. If this requirement
cannot be met but all previous supervisory re-
quirements are met, trouble should be sectional-
ized in the supervisory demodulator or in the dis-
tortion measuring circuit.
5. TROUBLE LOCATION TESTS
F1/F2 MODULATOR
5.01
If
the tests outlined in 4.01 to 4.16 fail to
indicate signals of the correct frequency or
level at the data test cord, troubleshoot the modu-
lator consisting of circuit packages CP31 to CP34
and associated pads and networks.
Page 16
5.02
The test procedures outlined here will indi-
cate that where a signal is not present on
an output of a circuit package it is not being gen-
erated by that unit. However, this condition can
also be brought about by an external short circuit
on the circuit package output. Therefore, tests
must be made to determine whether any short
circuits exist; in order to make these tests, it may
be necessary to remove the circuit package whose
output is being examined. Tests on the modulator
are conventional signal tracing tests, as input and
output test points are placed on all circuit packages
except the input to the binary counter. The test
may be made in any order in case there is reason
to suspect any particular unit.
5.03
For these tests, it will frequently be neces-
sary to gain access to the electronic counter
on the 20A toll testboard for frequency measure-
ments. This is done by plugging the LD cord into
the R jack and operating the FRS CHK key. The
frequency to be measured is then led from the
appropriate test point to the R test point on the
CPS.
5.04
CP34: With the ACTVM measure level the
same as that indicated in Test 2 of Table
A with the LEV-OUT key in the HI position
and the SUB AGC key normal on the AO test
points of CP34. This test should be done with the
switch settings that were made when the test
described in Test 2 of Table A failed. If no
signal is found on the AO test points, measure the
level on the AI test point to ground; this should
be 23 db below that expected on the AO test
points.
If
a signal is measured on the AI test
point, the amplifier on CP34 is out of order or
its output is shorted externally. If no signal is
found on the AI test point, a signal of -16 ±2
dbm should be measured on the MO test point.
If a signal is found at these test points, the filter
or pad circuitry and its associated wiring shown
on SD-73022-01, B5 must be checked for open or
short circuits. If no signal is found on these test
points, connect the 908A to the IN test point on
CP34. The 908A should indicate the frequency
shown in 5.05.
5.05
Should the signals below not appear, pro-
ceed to the BC test point on CP33 and make
the tests indicated .in 4.23 (f). In case of a spe-
cific failure in any one switch setting, CP31 is
(