Fostex G24S Service Manual page 26

4.3.2.5).
8) Calibrate tracks 2~24/2~16 in the same way.
4.3.4 Adjusting and Checking the Reproduce Frequency Response
1) Put Dolby NR ON/OFF SW to OFF position.
2) Playback the Frequency Response section of the Reproduce Alignment Tape.
* Caution: Please be careful that the Frequency Response section of the Reproduce Alignment
Tape, RL 41J326 is recorded lOdB lower than the Reference level position
(IKHz).
3) Plug in a level meter to the OUTPUT jack.
4) Adjust R206 (REP EQ) so that the reproduce level at lOKHz is same as the level at IKHz.
The normal playback frequency response should be within ±3dB for a frequency range of
125Hz ~ 16KHz. If it is not within the spec, adjust R206 (REP EQ) again.
4.3.5 Bias Leakage Check
Two bias trap modules are provided for each channel. One is in the first stage of the reproduce
amplifier and the other in the output stage of the record amplifier.
1) Reproduce bias trap module (UI 8)
To check bias leakage of TRACK 1, the oscilloscope probe is hooked to TP-2 and the
probe ground clip to the GND pin. Put TRACK 1 in the reproduce mode, the adjacent
TRACK 2 in the record mode and check bias leakage at TP-2.
It is considered as a normal condition if the bias leakage level is less than -1 OdBV.
(At checking TRACK 2, put adjacent TRACK 3 in the record mode).
If the bias leakage level is higher than the spec, it is adjusted to the minimum bias leakage
level by rotating the center core of U18. But before doing this, check the frequency (100
KHz ±0.5 KHz) of the erase/bias master oscillator. To check the oscillator frequency,
pull out the R/P card of the G24S, and check the frequency at connector J 2-8 on the
CONNECTOR BOARD PCB Assy.
2) Record bias trap module (U2 1)
To check bias leakage of TRACK 1, the oscilloscope probe is hooked to TP-4 and the
probe ground clip to GND pin. Put TRACK 1 in the record mode and check bias leakage
at TP-4.
It is considered as a normal condition if the bias leakage level is less than -8dBV.