Revox A77 Service Manual

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MONITOR
CM I C1.1•
NIM
MSS
Fig. 6.6-74
RECORD
M.
— AF- generator ( 500 Hz ). Switch 20 dB higher with
respect to previous setting I input voltage about 40 mV I
— Connect distortion factor meter to an OUTPUT terminal.
— Load tape, switch to RECORD ( Stereo) 7.5 ips.
— Measure distortion factor ( CH 1 and CH 2).
— Set input level so that the distortion factor is 2 % on
the worse channel at 7.5 ips.
— Repeat procedure with 3.75 ips. Distortion factor may
be 3 %. In case of higher values, reduce input level till
3 % distortion factor is achieved.
— Distortion factor control " Before- tape ": Set before- and
after- tape switch to INP. Distortion factor shall be 1 %
maximum !
— Switch back to NAB lower input level by 6 dB.
— Adjust METER CALIB ( fig. 6.6 — 75 ) with
CH 1 and CH 2, VU- meter indication 0 dB (
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6.6.2. Noise Voltage ( and External Voltage ) via Tape
Noise voltage measurements refer to full- modulation ( dis-
tortion factor 2 % at 7.5 ips, 3 % at 3.75 ips resp. per
6.6.1. )
— To avoid RF - interference errors, a tape erased on the
recorder is measured in the PLAYBACK mode.
...ONTO* RECORD
Cel CM•
WIN MIN
Fig. 6.6-76
Effective values ( weighted, CCIF filter) of the noise and
external voltages can be seen for the REVOX 601 tape in
the following table:
2 Track
7.5 ips
3.75 ips
4 Track
7.5 ips
3.75 ips
Noise Voltage
> 66 dB
> 63 dB
> 62 dB
> 59 dB
Ext. Voltage
> 58 dB
> 57 dB
> 56 dB
> 54 dB
Table 6.6-77
If these noise and external voltage separations are not
attained, the tape guide elements and magnetic heads are,
once more, to be demagnetized carefully.
6.6.3. Noise Voltage, External Voltage " Before- Tape"
( Check )
— Switch recorder to STOP.
— Before- and- after tape switch to INP ( fig. 6.6 — 78 ).
IMOMTOR
taw
Fig. 6.6-78
RECORD
MIN
The noise and external voltage separation shall be more
than 75 dB, referred to full- modulation.
Check of Input Amplifier :
— Set controls per fig. 6.6 — 79
— To avoid hum interference during this procedure, the
microphone inputs ( jacks or cinch connectors ) are to
be terminated with 200 ohm.
MONITOR
Fig. 6.6-79
CMANN CONI,NM.
RECORD
MAE sms
The noise and external voltage separations shall be more
than 45 dB referred to full- modulation.
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31

Revox A77 Specifications

General

Wow and Flutter	0.08% (7 1⁄2 ips)
Frequency Response	30Hz to 20kHz (7 1⁄2 ips)
Signal to Noise Ratio	60dB
Type	Reel-to-Reel Tape Deck
Track System	4-track, 2-channel stereo/monaural
Reel Size	Up to 10.5 inch reel
Motor	2 x reel, 1 x capstan
Inputs	Mic, Line
Outputs	Line
Tape Speed	3 3⁄4 and 7 1⁄2 ips