Adjusting The Dc Component Of The Focus Signal; Harmonic Distortion; Output Level; Frequency Response - Revox B225 Maintenance Instructions Manual

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B225
SECTION 4/11
The angle alignment must be corrected if the deviation
is too large:
- Unfasten screw [A] until the support plate [ B] can
be shifted.
- The support plate can now be shifted according to
Fig* 4.5. Retighten the screw [A] when the position
is correct.
- The angle alignment must be rechecked after the
foregoing adjustments have been made.
4.2.7 Adjusting the DC component of the focus signal
- Connect DC voltmeter to Rl (SERVO 1 PCB 1.76 9.310).
The following adjustment is only necessary if the DC
deviation exceeds +JL4 0 mV. Replace the motor if alignment
is not possible.
- Adjust the axial set screw of the disc motor in such
a way that 0 V +_50 mV is measured.
- If the motor is replaced, perform the adjustments
according to 4.2.6 and 4.2*7*
4.3 Measuring the audio data
4.3.1 Aids
-_ Reference CD, part No. 46240
- Automatic distortion meter (e.g. Tektronix AA 501;
the RESPONSE button must be in the RMS position for
all measurements)
- Measuring filter (for distortion measurement)
~ Frequency counter
- Oscilloscope
4.3.2 Harmonic distortion
- Measuring arrangement according to Fig. 4.16
- Adjust for maximum level with VOLUME + key
- Mount reference disc (part N o . 4 6 2 4 0 ) . Play track
4 for measuring the left-hand channel and track 8
for measuring the right-hand c h a n n e l .
- The harmonic distortion should be less than 0.006%.
4.3.3 Output level
- Press CAL TONE button and adjust for maximum level
with VOLUME + key.
- The level of the FIXED and VARIABLE outputs should
be 2 V RMS +10%. The balance between channels should be
better than 0.2 dB.
4^,3 . 4 -Frequency response
- Adjust for maximum level with VOLUME + key.
"'-—The calibration tone (1 kHz) serves as the 0 dB
reference.
- Play tracks 4 and 8 (CD part N o . 46240) and measure
the outputs FIXED and VARIABLE. The frequency response
shoul-d be within +0 to -X3.6 dB.