Fostex G24S Service Manual page 30

jack 1, 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 it is not within spec, demagnetize the head, check the bias trap adjustment and record
level.
If it still does not fall within spec after making the corrective measures above, readjust
the bias current by the procedures in Section 4.3.7.
4) When the Section 4.3.7 adjustments are made, it is necessary to go through procedures
in Sections 4.3.8 and 4.3.9.
4.3.12 Erasure easurement
1) Put NR ON/OFF switch to OFF.
2) To adjust TRACK 1, for example, apply a IKHz, OdBV (IV) signal which is lOdB hi gher
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 the start point of the recording, playback the tape and insert a IKHz band ­
pass filter between OUTPUT 1 and the level meter to measure the output.
4) The level ratio between the IKHz recording and the no-signal recording is the Erasure
figure. It is considered as a normal condition if Erasure is higher than 70dB.
5) If it is off the spec, increase Erase current about 10% by the procedure of Section 4.3.6.
onitor the Erase current waveform on the oscilloscope at adjusting and set the core
just before the waveform begins to deteriorate.
A higher current will heat the Erase head and result in damage to the tape. And check
the Head touch condition of tape.
4.3.13 Sync Crosstalk Check and Adjustment
1) Sync crosstalk is the relative figure, against the reference level, on how much of the
recording signal from the track in the recording mode is leaking into the track being
reproduced.
When sync crosstalk is excessively high, playback output during overdubbing will sound
muddy by effect of the recording signal leakage or cause oscillation at ping-pong record ­
ing (where the playback output is transferred to another track).
2) Put NR ON/OFF switch to OFF.