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Model 280B
Main tenance
at other times deemed desirable by the user.
In
multi-track machines, these procedures must be
repeated for each channel. The demagnetizing pro
cedure described in paragraph 4.4 should be per
formed prior to any checkout and alignment.
7.10 Test Equipment Required
The following test equipment, or equivalent, is
required to perform the checkout and alignment
procedures and for troubleshooting the machine:
• Standard alignment or test tape
• Audio Oscillator, Hewlett-Packard Model
204D
• AC Voltmeter, Hewlett-Packard Model 400F
• Flutter Meter, BHK Electronics Model F2
• Frequency Counter, Hewlett-Packard
Model 5245M
• Recording Tape, 3M 206
• Oscilloscope, Tektronix, Model 434 (20
MHz or better) with 10:1 probe
• Alignment tool, Scully Part No. 162235
(supplied with amplifiers)
• 400 Hz Filter, TRW Type No. BPM-400
• Volt-Ohm Milliammeter, Simpson Model 260
• Weighting Filter, ASA "A" Curve Standard
S1.4-1961
7.11 Preliminary Procedures
To perform the following procedures, make the test
setup shown in Figure 7 -11 and proceed as follows:
A. Thread a standard reproducer alignment tape
on the
recorder.
B.
Set controls as follows:
• CAPST AN speed selector switch to HIGH
• Function switch to SAFE
• Monitor switch to PLAYBACK
• PLAYBACK
LEVEL switch
to
CAL
C.
Open the electronics drawer for access to cali
bration adjustments (Figure 7-12).
,
t
400
H~
A
FILTER
l'
WEIGHTING
A
FILTER
SPEAKER
j~
AMPLIFIER
OR
HEADSET
OSCILLO
AUDIO
SCOPE
OSCILLATOR
I
0
0
6
LINE OUT
LINE IN
LINE OUT
LINE IN
J 120
JII9
JII8
JII7
'-----
CH 2
I
'-----
C H
I~
ELECTRONICS
ASSY
Figure 7-11. Initial Test Setup
7.12 Playback Alignment
A. Begin tape motion by pressing START push
button. Monitor the output on the external
ac voltmeter or recorder vu meter and
speaker.
B. Adjust the PLAYBACK LEVEL CAL
potenti
ometer (located in the center of the PLAY
BACK LEVEL knob) for 0 vu (+4 dBm) at
reference frequency and fluxivity on the re
producer alignment tape.
C. Adjust the azimuth of the playback head for a
maximum signal output on the ACVM using
the right-hand slotted-head screw located on
top of the head bridge mounting plate (Figure
7-13).
7-10
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