Teac A 770 Service Manual

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T EAC®

SERVICE MANUAL

A-7 70

Stereo Cassette Deck

Effective: December, 1980 500172 5704007300

P: X

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l-770

I SPECIFICATIONS AND SERVICE DATA

SPECIFICATIONS

Track System 4-track, 2-channel stereo

3 Heads Erase, record and playback

Type of Tape Cassette tape, 8-60 and 0-90 (Phillips type)
Tape Speed 4.8 cm/s (1-7/8 ips)

Input (Level and impedance)

MIC: Specified input level;-57 dB (1.09 mV)/10 kohms
Min. input level; -67 dB (346 MW

LINE IN: Specified input level; -9 dB (275 mV)/50 kohms
Min. input level; -19 dB (86.9 mV)

DIN: Min. input level; -45 dB (4.36 mV)

*Pursuant to DIN standards (Europe model only)
Output (level and load impedance)

OUTPUT: Spec. output level;-5 dB (436 mVI/50 kohms
Max. output level;-3.5 dB (518 mV)
PHONES: Spec. output leveI;-16 dB (123 mVI/B ohms
Equalization
METAL: 3130 us+ 70os
Co (Cr01): 3180 us+ 70 us
NORMAL: 3180 ps+120us

Heed Configuration
Ill-track, 1-channel erase head
1/4-track, Z-channel record head and playback head in a single housing
Motor 1 DC servo motor (for capstan drive)
1 DC motor (for real drive)
Bias Frequency 100 kHz t5 kHz
Operation Position Horizontal
Power Requirements
100/117/220/240V AC, 50/60 Hz, 21W (General Export Model)
117V AC, 60 Hz, 21W (U.S.A./Canada Modal)
220V AC, 50 Hz, 21W (Europe Model)
240V AC, 50 Hz, 21W (U.K./Austraiia Model)
Weight 7.0 kg (15-7/16 lbs.) net
Dimensions See Fig. 1-3

SERVICE DATA

MECHANICAL
Tape Speed Deviation 3,000 Hz :45 Hz
Tape Speed Drift 45 Hz
Wow and Flutter
Playback: 0.07% (WRMS)
Record/Playback: 0.20% (RMS)
Pinch Roller Pressure 350 g to 450 9 (12.3 oz to 15.9 ozl
Reel Torque

Take-up: 40 to 85 g-cm (0.56 to 0.90 oz-inch)
Supply: 2 to G g-cm (0.028 to 0.033 oz-inch)
F.F.: 120 to 170 g-cm (1.7 to 2.4 oz-inch)
REW: 120 to 170 g-cm (1.7 to 2.4 02-inch)

Fast Wind Time

95 sec. or less for MTT-501 (C-BD)
Auto End-stop Time 2 sec. or less
TIMER activate Time 2.3 sec. :1 sec.

ELECTRICAL
Frequency Response
Playback - Co (Cr0,), METAL

+4 +4ae
+2 ----\ -

o

-2

-4

(a) ' 5 9
##4##
40 63 SIS 2k 4k 6.3K 1011
Fig. 1-1
Overall
+ 4
+ 2
0
- 2
- 4
(dB)
40 63 l25 400 6.3K at 14*
Eli 25k
Fig. 1-2

Signel-to-noisa Ratio
Playback NORMAL: 46 dB min.
Record/Playback
METAL, Co (mm): 45 dB min.
NORMAL:43 dB min.
S/N is improved by 5 dB at 1 kHz and I0 dB above 5 kHz
when Dolby NR is used.
Erase Efficiency 65 dB min. at 1 kHz (measured with input 10 dB
higher than the specified input level).
Channel Separation 20 dB min. at 1 kHz
Adjacent Track Crosstalk 40 dB min. at 125 Hz
Total Harmonic Distortion 2.2% or less with METAL/Co (Cr0,)
2.5% or less with NORMAL

NOTES:

0 Improvements may result in SPECIFICATIONS AND SERVICE
DATA changes.

0 Value of "dB" in the data refers to 0 dB (0.775 V), except
where specified.

** Noise Reduction System manufactured under license from
Dolby Laboratories Licensing Corporation.
Dolby and the doubleAD symbol are trademarks of Dolby Labo-
ratories Licensing Coooration.

CAUTION
A Parts marked with this sign are safety critical components. They
must always be replaced with identical components - refer to the

TEAC parts list and ensure exact replacement.