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A-Chain Alignment Procedures
Step
No.
4-16
IndicationAction
b. Optical Preamplifier Adjustments
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OUT OF
FOCUS
INTO
FOCUS
X
✓
X
✓
X
14
15
Dolby
Rt
Lt
Lt
Rt
gnd
Proj. 2
hf
GAIN
hf
GAIN
Rt tp
Rt
Lt
Lt tp
Proj. 1
hf
GAIN
hf
GAIN
signal
present
Cat. No.
240A
REPEAT AND
1
12
1
13
Cat. No. 240
X
Y
Proj. 1 Status
RV101 Gain
RV102 hf
RV201 Gain
RV202 hf
TP501 L tp
TP502 R tp
R
L
RV301 Gain
RV302 hf
RV401 Gain
RV402 hf
Proj. 2 Status
TP503 GND
R
R
L
L
SIGNAL
PRESENT
RTA
SCOPE
IN
A-Chain Alignment Procedures
Notes
4-17
b. Optical Preamplifier Adjustments
The test in this step is performed both at the right and left channel test points of the Cat.
No. 240A card.
The frequency response must be within 1 dB to at least 12 kHz. Adjust the L hf and R hf
potentiometers on the Cat. No. 240A card for the most extended high frequency response
without “peaking.” If these adjustments do not improve the frequency response, the
problem may be a degraded slit or damage to the lens.
Disconnect the RTA from the left test point and connect it to the right test point TP502 R.
Then repeat Steps 12 and 13. NOTE: The azimuth and high frequency response must
be the same at both the left and right test points. If results are not similar, it may be
necessary to remove the lens and check for oil or contamination or a degraded slit.
Replace the lens, if necessary. Do not proceed to the next step until the outputs at
both the left and right test points are similar.
Appendix B shows the effects of slit geometry on frequency response.