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C-3X
5 ELECTRICAL ADJUSTMENTS AND CHECKS
PRECAUTIONS
1. Before beginning any checks or adjustments, clean and demag-
| ~70 4B or more. . . What does it mean?
netize the entire tape path.
In reference to some specifications, you may come across an expres-
2. Make
sure the deck is properly set for the voltage in your
sion fike: "—70 dB or more". This means that the lower the value
jocality.
of this specification, the greater the absolute value of the specifica-
3. In general, adjustments and checks are done in the order of L-ch
tion and the better the performance of the deck. For instance, a
then R-ch. Double REF. NOs, and test point designations indi-
noise floor of —76 dB is better than —70 dB, because this means
cate L-ch/R-ch.
that the level of noise is lower. So in this case, "~70 dB or more"
(Example: R11/R21)
means at least as good a value as —70 dB and maybe even better,
4. For this deck, 0 dB is referenced to 0.775 V. If you are using an
i.e., —-71 dB.
AC voltmeter which references 0 d8 to 1 V, appropriate com-
pensation should be made.
5. The AC voltmeter used in the procedures must have an input
impedance of 1M ohms or more.
6. Note the "Deck settings" at the top of each chart. These settings
must he used for all the checks in each chart unless explicitly
stated otherwise.
OSCILLOSCOPE
OSCILLATOR
DISTORTION
ANALYZER
Oo
ieee
ie)
@® ee
eee
©
°
AC
Voltmeter
ATTENUATOR
LINE
IN
OUTPUT
Fig. 5-1 Basic test setup
REC-PLAY
Head
OSCILLOSCOPE
AMP
SPKR
Height/Tilt
Adjusting Screw
Azimuth
OUTPUT
AC Voltmeter, ..,
Adjusting Nut
T-1769
Fig, 5-2 Test setup for azimuth check
Fig. 5-3 Azimuth adj. nut location
|
ws wm
Deck settings:
TEAC test tapes:
MONITOR sw.:
TAPE
MTT-150:
For Dolby level calibration
NR SYSTEM sw.: OUT
MTT-316:
For playback frequency response
SPEED sw.:
STANDARD
check for METAL, Co(Cr0,)
5-1 PLAYBACK PERFORMANCE
- EO sw.:
METAL
MTT-216:
For playback response check for NORMAL
MEASURING
ADJUST
POINT:
{or CHECK)
ITEM
SETTING
INPUT SIGNAL
Conn.:
Fig. 5-2
RESULT
OUTPUT:
1. REC/PLAY
head
azimuth
OUTPUT cont.:
convenient
MTT-316
(12.5 kHz)
output level position
3. Specified output
level
OUTPUT:
MTT-316
Fig. 5-9
R10/R20
Azimuth nut of
@ Phase: about 0°
R-P heads
on 'scope (Fig. 5-4)
(Fig. 5-3)
@ Max. output on
Phase:
45° min.
(315 Hz}
90°
min.
4. PEAK
LEVEL
meter
MTT-150
'
EQ: METAL, Co(CrO,}
Adjust for 10 kHz to be the
OUTPUT:
At 10 kHz,
should be 3 d8 to6dB
VTIVM
OUTPUT:
2. Phase shift
Same as above
MTT-316
Check
{12.5 kHz)
TP1/TP2
MTT-
R1
ies
viene
~2.5 dB (581 mV)
*Spec. setting of
OUTPUT:
OUTPUT cont.
~5 dB (436 mV)
© Spec. output
level
same level as ref. signat
(315 Hz)
higher than measured
in above step,
5. Frequency response
EQ:
NORMAL
MTT-316
SPEED:
STANDARD and
Fully-erased tape:
OUTPUT:
HIGH
(Use bulk tape eraser)
ys
52 dB min. {STD}
Ratio of spec.
6. Signal-to-noise ratio
|EQ: METAL
.......~...
. METAL
.....,
55 dB min. (HI}
output of
Col(CrO.)
.........
. .MTT-5061..... }
48 dB min.
~5 dB to noise
NORMAL
.........
. MTT-50%
.....
a
53 dB min.
PHONES:
—15.8 dB +3 dB
(89.0 mV to 178 mV}
7.- Headphone output
level
MTT-150
Check
AC Voltmeter
0° (IN PHASE)
45°
90°
180°
DECK under TEST
PHONES
Fig. 5-4 Confirming phase relationship
Fig. 5-5 Test setup for headphone check
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