Bell 28E Adjustments page 29

Signal Contacts - Electrical
2. 26 The strobing adjustment procedure is
used for checking and adjusting
contacts electrically,
refining the mechanical
transmitter distributor. The same procedure
is used for checking both the marking and spac­
ing pulses for both 5 and 6 level, and all unit
codes. Differences exist, however, in the num­
ber, width, and tolerance of pulses, and in the
allowable break width. The data appropriate to
each level and unit code is tabulated on the as­
sociated Pulse Data Table.
given in Paragraphs 2. 2 7
general procedures
and 2. 28 following, and using data from the ap­
propriate table, the marking and spacing pulse
adjustment can be made for all units.
trate the procedure further, the data appro­
priate to a 5-level, 7.42 unit code
parenthetically as an example in the general
adjustment procedure following.
Note: Gold-plated signal
not be electrically adjusted unless there is
an intermediate device available which, when
keyed by the signal contacts, will interrupt
the current to the stroboscopic test set. The
intermediate device must be capable of being
keyed by a 3- to 20-volt change in voltage at
a current not in excess of 20 milliamperes.
The standard stroboscopic test set operating
voltage must not be applied directly to the
signal contactSbecause of the possibility of
damaging the contacts' gold plating and thus
impairing their operating efficiency in this
low-energy level application. (Refer to Para­
graphs 1.08 through 1.13.)
2. 2 7 Marking Pulse Adjustments
(a) Plug a signal distortion test set having
the appropriate scale (eg, 7 .42) into the
signal line so that the marking contacts of
the transmitter-distributor unit under
will interrupt the current to the stroboscopic
lamp within the DXD. Have the transmitter­
distributor transmitting
ously and the test set and transmitter -dis­
tributor operating at the same speed
w pm). Rotate the test scale to align the 0-
scale mark of the START segment (end of
STOP segment) with the end of the stop pulse
image indicated by the rotating strobe light.
Note: The end of the stop pulse image
should not vary more than one division in
signal
a nd at the same time,
adjustments for the
By following the
To illus­
is added
contacts should
test
or "R" continu­
Y
" "
(100
ISS 5, SECTION 573-127-703
either direction when the scale is posi­
tioned so that the
about the 0-scale mark of the START seg­
ment.
(b) Check the position of each of the pulses
against the position
pulse should be in its designated segment on
the test scale, within the specified tolerance
figure (eg, 15 div) .
Note: Each marking code pulse may have
one break, provided the break is not longer
than the allowable
(eg, 1 div) and the break comes within the
tolerance range (eg, 5 div) and the end of
the pulse.
(c) To adjust, loosen
mounting screws until they are friction
tight. R otate the eccentric of the contact box
mounting bracket toward the right or left un­
til the requirements are met.
mounting screws and recheck the adjustment.
CONTACT BOX
ECCENTRIC
SCREW
CONTACT BOX
MOUNTING
SCREW
(Front View)
Note: If these signal requirements cannot
be met, refine the TRANSMITTER DIS­
TRIBUTOR GEAR BACKLASH (2. 3 2 ) ad­
justment (See BASES) and the TRANSFER
BAIL
viewing the signal on the test set.
2. 28 Spacing Pulse Adjustments: The general
procedure for adjusting the spacing pulse
is identical to that outlined for marking pulses.
The tolerances for spacing pulses may not be
the same as for marking pulses however. Refer
to the appropriate Pulse Data Table when making
adjustments.
variation is centered
tabulated. Each
break width specified
the two contact
box
Tighten the
SIGNAL
CONTACT BOX
(2. 21 ) adjustment,
Page 29