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9.10.5 Vertical Adjustment of Exciter Lamp
For forward scan readers, set the oscilloscope to the X-Y display mode, and connect the same signals to
the RTA (real time analyzer, spectrum analyzer). Play a loop film recorded with (black-and-white) pink
noise signal, and adjust the output level from the analog pickup to the point where the highest frequency
characteristics become. If necessary, adjust to the preferred frequency characteristics.
9.10.6 Slit Lens Adjustment
Adjust the focus of the slit lens of the pickup where the frequency characteristics of the pink noise
becomes the flattest. Rotate the slit lens so that the phase difference becomes minimum on the X-Y
oscilloscope, and adjust the azimuth of the slit.
9.10.7 Double Checking of Illumination Inconsistency
Even illumination from the slits is essential to reducing high level distortion and in the decoding of
surround signals from the Lt/Rt. Falloff at the outside edges will result in high frequency loss and play-
back that sounds muffled. Assuring proper playback of high levels is especially important, as modern
analog track cameras can readily print stereo tracks at 130 % modulation without loss of the septum, and
this extra range is commonly utilized.
To check for proper illumination, play a 100 % modulation alignment film, such as the Cat. 97 left/right
film, and also a 50 % or 60 % modulation alignment film, such as the Cat. 69T. The levels of the left
signal and right signal should be equal to each other when playing either film. If they are not, the slit
image is imperfect in illumination flatness or in its alignment on the solar cell. The result will be distor-
tion of loud sounds and leakage into the surround speakers.
This same test can be done using the old evenness of illumination test film, also called the "snake loop"
or in Europe "scanning beam," (SMPTE Test Film No. P35-SB) though this film was designed for mono
solar cells. The most direct means of testing for evenness of illumination may be the Cat. 566 Illumina-
tion Uniformity test film. This film does not have conventional stereo tracks; instead it has six tracks of
100 Hz to 4 kHz spread across the entire optical track area. The Lt and Rt outputs are to be summed and
sent to a spectrum analyzer, where the relative heights of the six bands gives direct indication of illumina-
tion of the slit across the entire solar cell.
9.10.8 Wiring Check
As a basic wiring check, slowly block the reader's sound lens and note that the right channel level drops
before the left channel.
This completes the mechanical adjustments of the analog track reader, but remember that these adjust-
ments interact and it may be necessary to repeat these procedures to obtain the very best performance.
9-53
DFP-3000
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