2001 Wohler Technologies, Inc. ALL rights reserved
5
2. Adjust the front panel H position control so that the vertical line trace is in the center of
the CRT. Simultaneously adjust the front panel V position control and the scope Y
calibration pot, R66, until the vertical line trace extends from the bottom of the CRT to
the diagonal "IN PHASE" graticule line.
3. Reconnect the test oscillator input to channel 2, right input. Simultaneously adjust the
front panel V position control and the scope X calibration potentiometer, R90, until the
line trace is perfectly parallel with the "IN PHASE" graticule line.
4. Adjust R62 and R86 to set the left and right VU meters to 0 VU.
5. Set the test oscillator output amplitude equal to the line level, which is considered to be
the studio "clip" or distortion level (+18 dBm, +24 dBm, etc.). Adjust R65 and R89 so
that the top red LED’s on the left and right columns are just lighted.
NOTE: Steps 6 and 7 are to adjust LED column linearity and are not required for "touch up"
or when changing to a new line level standard.
6. Reduce the test oscillator output amplitude by 24 dB. Adjust R114 and R142 so that the
24 dB LED on the left and right LED columns is just lighted.
7. Increase the test oscillator output level by 3 dB. Adjust R113 and R141 so that the 21 dB
LED on the left and right LED columns is just lighted. Repeat steps 5, 6 and 7 until no
further improvement in calibration accuracy can be obtained.
