Fostex B-16 - Page 43

5. 4.9 Overall S/N measurement
1) Set the front panel NR INT/EXT switch at INT.
2) Upon completing checks up to Section 5.4.8, apply a IKHz, -LOdBV (0.3V) signal
to the rear panel INPUT jack 1 (example for track 1), record the signal onto a
blank tape, then, without stopping the tape, unplug the oscillator connected to
the INPUT jack and further record a length of no-signal on the tape.
3) Plug a level meter into OUTPUT jack 1, play back the recorded signal section to
measure the noise level of the no-signal section against the IKHz reference
level, add lOdB to it and obtain the ratio between peak recording level and
noise level.
Specification: 80dB weighted
60dB unweighted
5.4.10 T.H.D. measurement
1) Set the front panel NR INT/EXT switch to INT.
2) to adjust TRACK 1, for example, apply a IKHz, -LOdBV (0.3V) test signaL to INPUT
jack L, record it, playback the recorded tape and apply its output from OUTPUT
jack 1 to the distortion meter.
Specification: T.H.D. 1% or less
3) If response is not within spec, demagnetize the head, check the bias trap adjust 
ment and record level.
If response still does not fall within spec after taking the corrective measures
above, readjust the bias current by the procedures in the previous Section 5.4.6.
4) When the Section 5.4.6 adjustments are made, it is necessary to go through
procedures in Sections 5.4.7 and 5.4.9.
5.4.11 Erase measurement
1) Set the rear panel NR INT/EXT switch to INT.
2) To adjust TRACK 1, for example, apply a IKHz, OdBV (IV) signal which is lOdB
higher than the reference level, to INPUT jack 1 and put TRACK 1 in the record
mode .
Partially rewind the tape to retain a section of the IKHz signal and then record
over the remaining section without any signal at the input.
3) Rewind to start of recording, playback the tape, insert a IKHz bandpass filter
between OUTPUT 1 and the level meter to measure the output.
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