Revox A77

ALIGNMENT INSTRUCTIONS REVOX A 77 DOLBY
Hem Operation
Alignment Procedure
Test Equipment
Tape
Speed
ips
Frequency
Voltage Testpoint
Where to adjust
1. Adjustment of regulated •
Voltage
Adjust exactly to nominal
21 volts
Multimeter 7.5
+ 21 V DC
Yellow wire
ED 1
P 106
2.
Adjustment of Tacho Head
(S.M. 6.2.1.)
Alter head position to obtain
specified tacho voltage
Electronic Volt-
meter
3.75
40 m V AC El - E2
mounting screws
of tacho - head
3.
Bias- Filter record
(S.M. 6.4.3.)
Adjust for minimum voltage Electronic Volt-
meter
7.5 120 kHz
< 300 mV
see fig.
6.4.-63/64
L 501
4. Bias- Filter, replay
(S.M. 6.4.4.)
Adjust for minimum voltage Electronic Volt-
meter
7.5 120 kHz
< 50 mV
Wiper P 801 L 801
5.
Motor Speed
(S.M. 6.2.2.)
Adjust tacho frequency ( mea-
sure over at least 10 sec.)
Digital Counter 7.5
3.75
1601 Hz
800 Hz
10 V Pin 2 on T 201
T 201
P 201
6. Oscillator and
Bias adjust
As per Service Manual 6.4.
Adjust dummy load
Electr.Voltmeter
Digital Counter
Digital Counter
7.5
7.5
7.5
120 kHz
120 kHz ± 5 kHz
120 kHz ± 5 kHz
2 Track 21 VAC
HB3-HB6
HB3-HB6
HB3-HB6
blue & orange wire
Dummy load L 601
7. DOLBY record adjustments
DOLBY " OUT"
DOLBY " IN"
Turn FET-bias off, set gain
control to minimum amplification
DOLBY switch 0 in position
"OUT"
Connect Audio Generator to
"AUX" inputs,
Adjust level on Generator
Adjust level on Generator
DOLBY switch in pos. " IN",
measure voltage rise on
DOLBY output
Level adjustment
Level reduction by 2 dB
T19
T 19 VTVM
T 19 VTVM
T 19 VTVM
T 19 VTVM
T 19 VTVM
5 kHz
5 kHz
5 kHz
5 kHz
5 kHz
5 kHz
'N. , 0.45 mV
3 mV
2.6 mV
'‘, 7 mV
(+8 dB)
8.2 mV
(+10dB)
-2 dB
P1, P2
P3, P4
P3, P4
P3, P4
P3. P4
P 101 r ( CH I, CH II)
P 102 r ( CH I, CH II)
Generator
Generator
Generator
P 102 r
P 101 r
8. DOLBY replay
adjustments
DOLBY " OUT"
DOLBY " IN"
Turn FET bias off,
Set gain control to min.
amplification.
DOLBY switch 0 in pos. " OUT"
Connect Audio Generator to
DOLBY inputs ( with test clips).
Adjust level on generator
DOLBY switch 0 in pos. " IN"
Adjust level reduction on
DOLBY outputs
Level increase by 2 dB
T 19
T 19 VTVM
T 19 VTVM
T 19 VTVM
5 kHz
5 kHz
5 kHz
5 kHz
7.6 mV
-10 dB
= 2.4 mV
+2 dB
= 3 mV
P5, P6
P7, P8
P7, P8
P7, P8
P 101 p ( CH I, CH II)
P 102 p ( CH I, CH II)
P 102 p
P 101 r
9.
VU- Meter calibration
Connect Audio Generator
to " AUX" inputs,
Adjust generator output level
Calibrate VU- meters
T 19 or generator
1 kHz
1 kHz
1 kHz
'\, 13 mV
100 mV
0 VU
P1, P2
P 103 p
10.
11.
Balance Adjustment
Playback head azimuth
adjustment
As per Service Manual
sections 6.3.1. and 6.3.2.
DOLBY reference
tape
12.
Playback level off test tape Playback level calibration
VU- Meter
7.5
185 nWb/m
= 0 VU
P 801
print 077.720
13.
Frequency response check
As per Service Manual 6.3.4.
and additional instructions.
14. Record head azimuth
adjustment
"REC. CAL" pot- meters CD/Ce4
fully ccw.
T19 generator level ('\ , 13 mV)
adjusted for 0 VU indication.
Reduce generator level - 20 dB
Adjust azimuth as per S.M. 6.5.3.
10 kHz
10 kHz
VU = 0 dB
-20 dB
15. RF Bias Adjustment
As per Service Manual 6.5.2.
A U for Scotch 207
T19
_
7.5
3.75
4 dB
5 dB
OUTPUT
CH I, CH II