11
INSTALLATION & OPERATION
SOUNDHEAD ALIGNMENT:
1. Play a S.M.P.T.E. Buzz Track loop. Adjust the lateral
film guide assembly or exciter lamp assembly.
Monitor the preamp signals with the oscilloscope.
Adjust for minimum signal on the left and right chan-
nels. Refer to specific instructions in the projector
soundhead manual. Minor variations in alignment
procedure depend on the individual mechanical
design of the soundhead.
2. Play CAT.# 97 Stereo Cell Alignment Film. Move
solar cell laterally and vertically until you
have achieved minimum crosstalk between
channels (see diagram 1).
3. Repeat steps 1 and 2 until no further
improvement can be obtained.
4. Play Pink Noise side of CAT.# 69 Test Film.
Switch oscilloscope to X/Y Mode. Adjust
soundhead optical lens azimuth for narrowest
diagonal trace (see diagram 2). Observe the
real time analyzer and focus the lens for maxi-
mum high frequency output while maintain-
ing the best azimuth. This is not easy, but it is
one of the most critical adjustments affecting
the overall system performance and is often
not done as well as it should be.
5. Adjust the vertical and lateral alignment of
the EXCITER LAMP for maximum output on
both channels. This is especially critical with a
narrow slit optical lens because there is a much small-
er “window” for the light to pass through.
6. Check the high frequency output on both channels.
Make sure the response is the same on both channels.
With a narrow slit optical lens, the response should be
flat within ± 3 dB to about 12 kHz with NO slit loss
correction. If not, this MUST be corrected before pro-
ceeding with the next steps. It is not permissible to use
slit loss correction to correct poor high frequency
response caused by misalignment of the optical
soundhead. An EXCITER LAMP out of alignment, the
barrel of the optical lens crooked, or oil in the optical
lens will all affect output and balance.
SLIT LOSS CORRECTION:
Run the Pink Noise side of the CAT. # 69 Test Film.
Observe the frequency response on your RTA which
should be still connected to the preamp testpoints.
Adjust the left and right slit loss correction trimpots
on the PREAMP CARD for optimum flat high fre-
quency response. Do not over adjust the slit loss cor-
rection in an effort to obtain extended response. This
will result in an undesirable frequency response peak.
Note: While adjusting the slit loss correction, aim for
as flat a high frequency response as possible. If one of
the preamp channels is slightly worse than the other,
then adjust the better responding preamp to match the
lesser. This will ensure that the matrix steering in the
MODIIC will be as accurate as possible.
OPTICAL PREAMP CALIBRATION:
Run a Dolby CAT. # 69 Test Film, Dolby tone side.
Diagram 1
Low crosstalk between channels
Diagram 2
