Fostex B-16 - Page 40

If the trace length between (1) and (2> are not the same, it means that the two
inputs are not of the same level. Correct for equal lengths by the oscilloscope
controls
If the playback head azimuth is out of alignment, the following patterns will
result:
(A SMALL MISALIGNMENT
30' OUT OF PHASE!
IA LARGER ERROR
90" OUT OF PHASE)
Fig
(A BIGONE, 180 ’
OUT OF PHASE)
(PERFECT AZIMUTH
0*, IN PHASE)
5.15
As a result of phase check with a lOKHz signal, the adjustment is finished if
difference in phase is less than 90 ’ between tracks and azimuth adjustment is
at the best point.
4) Check the playback frequency response of each channel by playback of the Frequency
Response section of the Reproduce Alignment Tape. The recorder BAR GRAPH meters
can be used for this check, but if a more accurate measurement is necessary, the
level meter is plugged one by one into the recorder rear panel 1 % 16 OUTPUT
jacks and the levels are then measured here.
The normal playback frequency response should be within ±3dS for a frequency
range of 40 "V 18,000Hz.
If response is not within spec, adjust REP EQ R103, 5 k I2 b .
5) Whenever R103 is adjusted, the Dolby encode must be recalibrated.
5.4.4 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, U5
To check bias leakage of TRACK 1, the oscilloscope probe is connected to TP-3
and the probe ground clip to the nearest GND.
Put TRACK 1 in the reproduce mode, the adjacent TRACK 2 in the record mode and
check bias leakage at TP-3 and trim the slug of U5 for a minimum reading. (At
checking TRACK 2, put the adjacent tracks 1 or 3 in the record mode.) If the
37