Black Box ACS235A - Manual (Page 78)

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CHAPTER 4: Configuring the ACS236A
4.2.1 R
EMOTE
G
AIN
-C
ONTROL
J
UMPER
B
ANK
JP8
If you’ll be using automatic gain control (AGC) in your Extender system, leave the
jumpers ON the right-hand posts of each of the three pairs of JP8 jumper posts, as
shown below. (This is the factory-default setting as well as the recommended
setting.) But if you’ll be controlling the gain manually (see Section 6.2), which is
necessary with VGA input and Sun output (see Section 4.1.1), move the jumper to
the left-hand posts of each of the three JP8 jumper-post pairs, as shown in
Figure 4-6.
When you have AGC selected, the Remote Module ignores the gain-control
screwdials on its rear panel and automatically adjusts the gain of each of the three
color signals, which is possible because each of the signals has the same white
reference value (0.7 Vpp) that the Module can use for comparison. If the colors of
the picture on your monitor still seem a little off, you can tweak them with the
Remote Module’s brightness and contrast controls, in addition to any color
controls on the monitor itself.
When AGC is turned off, the Remote Module’s gain-control screwdials become
activated, and you can use them to control the gain of the corresponding colors.
(Be aware that when you’re in this mode, chromatic aberrations can affect your
display.) Adjust the gain and check your adjustments by either watching the
monitor or, to get best results, by using an oscilloscope. See Section 6.2. As always,
you can also use the Remote Module’s brightness and contrast controls. We don’t
recommend that you turn AGC off unless (a) you are using VGA input with Sun
output, or (b) you have a color problem that you can’t seem to solve by any other
means.
Whichever way you set these jumpers, make sure that jumper JP3 in the Local
Module is set the same way.
Figure 4-6. Setting gain-control jumper bank JP8.
Jumpers on right-hand posts
J8
Jumpers on left-hand posts
With AGC (factory default) Without AGC