Scully 280B Series User Manual

7-12
Maintenance
Figure 7-13. Equalization PWA Adjustments
D. Following instructions from the standard test
tape, adjust equalization for flattest response.
Adjust HF HI for high speed and HF LO at
low speed (Figure 7-13). Low frequency ad-
justments should be made in Record mode in
order to compensate for fringing effects on
multi-track machines.
E. Set Function switch to SYNC position.
F. At corrected (250 nWb/m) reference tone
from the standard test tape, adjust sync level
potentiometerR7(Figure 7-14) on the record/
playback amplifier PWA for 0 vu, (+4 dBm on
external meter).
NOTE
The standard opera-
ting level (play back
fluxivity) is as follows:
3.75 & 7.50 in/s == 200 nWb/m at 1000 Hz
7.50 & 15 . 00 in/s == 250 nWb/m at 1000 Hz
15.00 & 30.00 in/s == 250 nWb/m at 1000 Hz
Model
280B
7.13 Record Alignment
A. Connect oscilloscope to the yellow test point
(TP1) on the regulator, bias oscillator , and
amplifier PWA (Figure 7 -15).
B.
Adjust bias level potentiometer RIO on the
regulator, bias oscillator, and amplifier PWA
for 40 volts p-p using the oscilloscope.
C.
On four-track systems, repeat steps A and B
to adjust R6 on the bias amplifier PW A (F ig-
ure 7-16) for channels three and four.
D. Install 3M 206 tape or equivalent.
E. Set Function switch to RECORD and CAP-
STAN speed switch to HIGH.
F. Press START and then RECORD pushbut-
tons on transport.
G. Visually align record head height to corres-
pond with playback head.
H. Record 15 kHz at -10 vu.
I. Adjust record head azimuth and check head
rotation for proper gap contact .
7.14 Record Bias Set
A. Record 10 kHz at approximately zero vu
level with Monitor switch in PLAYBACK
position (-10 vu for 7.5 to 3.75 in/s machines).
B.
Rotate R6 bias adjust on the record/playback
amplifier PWA (Figure 7 -14) until a peak read-
ing is
indicated on the vu meter.
C. Rotate the bias adjust potentiometer in a CW
direction (increasing bias) until the level on
the vu meter drops exactly 4 dB for 3.75 to
7.5 in/s machines at the 7.5 in/s speed, and
2 dB for 7.5 to 15 and 15 to 30 in/s machines
at the 15 in/s speed.

Scully 280B Series Specifications

General

Brand	Scully
Model	280B Series
Category	Turntable
Language	English