Revox A77 Service Manual

6.6.4. Erase Attenuation
Following Measurements: Erase attenuation, crosstalk, mono
and stereo ( 6.6.4 — 6.6.6. ) can be taken with a selective
v- rvrei ( band width less than 100 Hz ).
To measure erase attenuation, a frequency of about 1000
Hz is recorded and consecutively erased. The record remai-
ning on the tape is then measured.
— Set controls per fig. 6.6 — 80
— Record 1000 Hz, full- modulation.
MONITOR
MAX
Fig. 6.6-80
C MAMA I. I
RŒCORD
MAX
MAX
— STOP, rewind tape.
— Close record volume controls ( fig. 6.6-81 ).
Fig. 6.6-81
MIN
MIN
— Switch recorder to Record and measure the erase atte-
nuation.
The remainders on the tape shall be better than 75 dB
under the level of full- modulation.
6.6.5. Crosstalk, Mono I selective per 6.6.4. )
A mono- recording 1000 Hz full modulation is appropriately
taken 1 min on CH 1 and afterwards 1 min on CH 2 for this
measurement on a factory- tape. Note that the record butt
on the unused channel is disengaged.
— Set controls per fig. 6.6 — 82.
MONITOR
%XXX
Fig. 6.6-82
M.
Set playback function switch to CH 2, measure the cross-
talk separation 1 - 2 and bring with crosstalk compensa-
tion trimmer ( fig. 6.6 — 83 ) to best value ( more than
60 dB ).
o
o
e
Fig. 6.6-83
— Advance tape to recording on channel 2.
— Set playback function switch to CH 1, measure cross-
talk separation 2 - 1, correct P 305 if necessary.
For strong corrections, repeat crosstalk 1 - 2 measurement
and adjust for mean value.
6.6.6. Crosstalk, Stereo ( selective 6.6.4. )
Measure and if necessary adjust mono crosstalk attenuation
per 6.6.5. before checking the stereo crosstalk attenuation.
Don't disturb P 305 compensation trimmer during the
following measurements.
— The generator is switched in parallel on the AUX - inputs
while measuring stereo crosstalk attenuation. Close the
input to the channel to be measured.
— Set controls per fig. 6.6 — 84.
MONITOR
MAX
Fig. 6.6-84
RECORD
MAX
MIN
klAx MIN
— 11 "- - I - II — 0- II - I
— AF- generator 1000 Hz, full modulation, record stereo.
Measurement 1 — 2 :
— AF frequency millivoltmeter at output CH 2, record
volume control CH 1 fully open ( at right limit ), record
volume control CH 2 fully closed ( left limit ).
Measurement 2 — 1 :
— AF frequency millivoltmeter at output CH 1, record
volume control CH 2 fully open ( at right limit ), record
volume control CH 1 fully closed ( left limit ).
— Crosstalk attenuation shall be better than 45 dB.
T
I
1
al
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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