Scully 280B Series User Manual

Model 280B
Maintenance
SECTION 7
MAINTENANCE
7.1 MECHANICAL ADJUSTMENT
7.2 BRAKE ADJUSTMEI\lT
A.
Loosen both brake disc setscrews. Set the dis-
tance between the torque motor plate and the
disc hub using brake disc gage part no. 400519.
Tighten the setscrews.
B. Adjust the brake spring tension equally on the
supply torque motor assembly by loosening
the lock nuts (see FiglUe 7-1) and turning both
brake adjustment acorn nuts equal amounts,
so
that the friction holdback torque is as shown
shown in Figure 7-2.
C.
Repeat steps A and B for the take-up torque
motor so that the friction is as shown in Fig-
lUe 7-2.
Measurements should be taken at a
constant rotational speed just above breaka-
way condition. Torque can be measured us-
ing a
suitable spring scale to give the reading
noted on breakaway. The brakes should be ex-
ercised and the torque checked in the direc-
tion shown.
D. Tighten the lock nuts.
E.
Load a 10 .5-inch reel of tape on the transport.
Set the controls for the fastest tape speed and
operate the machine in the Play mode. Press
the STOP pushbutton . If the brakes are ad-
justed properly, tape motion will stop smooth-
ly
with the tape properly packed on the reels.
7.3
Tape Head Assembly Adjustments (Figure 7-3).
The tape head assembly is completely aligned at the
factory. No changes are necessary except for the
azimuth alignment, which should be checked peri-
odically
to assure continued peak performance. Re-
placement head assemblies are supplied completely
assembled
and prealigned. After installation, only a
mounting and rotation check is required.
A. Azimuth is adjusted by means of roundhead
screws (5) that pass through access holes in the
head bridge mounting plate (3) on either side
of the center fastening screw (7). The left-
hand screw has a spring which floats the left
side of the head assembly. Only the right-hand
screw is used to adjust the azimuth.
B.
Zenith is adjusted by means of two Allen set-
screws (4)
that pass through access holes in
the head bridge mounting plate (3) on either
side of the center fastening scre' . '" and 90 de-
grees
from the azimuth adjustment screws (7).
Initially, when installing a magnetic head, the
setscrews (4) are released so that the base of
the head can be brought up solidly against the
head mounting block by tightening the right-
hand azimuth screw (5). Turn the zenith set-
screws
(4) until they make contact with the
head base. From this point, t1p'n each zenith
setscrew one half turn, then release the right-
hand azimuth screw an equal amount to pre-
vent head distortion and damage. Repeat this
procedlUe a half turn at a time until proper
head height is reached. Visually check head-
to-tape alignment to determine proper head
height.
C. Tangency of each head gap to the tape is ad-
justed by loosening the 10-32 socket head cap
screw (7)
above the center of the head stack
and rotating the stack. Adjust the playback
head for maximum signal on the vu meter while
reproducing a high frequency signal from a
standard tape. After the playback head has
been adjusted, adjust the record head while re-
cording a high frequency signal and observing
the output on the playback head. Adjust the
erase head for a maximum efficiency in eras-
ing
previously recorded information.
D.
Position the scrape filter (10) for the lightest
tape contact at which it can follow the tape
speed . Although difficult to measure, wrap of
7-1

Scully 280B Series Specifications

General

Brand	Scully
Model	280B Series
Category	Turntable
Language	English