Leitch FR-684AV - Safety Terms and Symbols in this Manual

28 680 Series Video Distribution Amplifiers Installation and Operation Manual
Chapter 7: VEH-683 Wideband Video Distribution Amplifier Modules
Installation
VEH-683 video distribution amplifier modules can be installed in these frames:
• FR-683 – 4 video DA modules mounting frame
• FR-684 – 10 video DA modules mounting frame
• FR-684AV – 5 video and 5 audio DA modules mounting frame
There is no need to terminate unused outputs, but a perfect response can be
obtained if unused outputs are terminated.
Configuration
The VEH-683 module can be installed in any of the FR-680 series distribution
amplifier mounting frames. It must be terminated at the loop through input by a
75Ω terminator and it is recommended to terminate all the unused outputs.
Its primary setup is
• Gain: Unity
• Cable Equalization: None
• Video Signal Standard: NTSC
• Clamp mode: AC
The following adjustments are available: Gain Adjustment, Cable Equalization,
Clamping Mode, and Resetting the Clamping Pulse.
Gain Adjustment
The Gain can be adjusted by R4 with the range of ±3.0 dB.
Cable Equalization
The Cable Equalization can be adjusted by R5 with the cable length range from
0 to 328 ft (100 m) Belden-8281 cable or equivalent.
Clamping Mode
Back Porch Clamping Mode can be selected by J1, either soft clamp, hard
clamp, or no clamp.
If this distribution amplifier works in Clamping Mode and with PAL signal, the
clamping pulse circuit needs to be reset.
Reset the Clamping Pulse
Set the input coupling mode to AC.
1. Observing the signals at Pin 3 of U5 and Pin 8 of U3 simultaneously on the
screen of an oscilloscope that has two traces and at least 20 MHz
bandwidth, adjust R24 and R23 to obtain the waveforms shown in
Figure 7-2.