User Manual

Unit 7 – Cabling and attributes
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3. TV monitor:
3.1. Function:
The TV monitor function is to detect the output RF signal and final amplifier, providing the video
carrier output power reading and audio carrier and the video signal monitoring that have been
transmitted.
3.2. Technical Description:
The obtained signal through the directional coupler supplies the monitor input, by connector J1.
The resistors R14 and R15 provide 50 Ohm termination for interconnecting cabling. The diodes
D2 and D3 function is to detect the RF signal and they are polarized to a better linearity through R1,
R2, D1, C1 and L1. The linearity adjustment is made by R4.
The detected signal by D2 supplies the detector peak circuit via R4, formed by IC1, IC2A and
associated components in order to obtain the output peak sync power reading from the power stage.
Through R12, the reading is adjusted to the panel. The detected signal by D3, after passes by
Q1, that provides high impedance to D3, it supplies the 4.5 MHz filter formed byL2, C26, C27, C12,
R18 and R19. The filter can be short cut by CH1.
The video signal through trimpot R20, supplies the video IC6 that through R38 shows a 75 Ohm
output impedance.
3.3. Adjustment Procedure:
a) The trimpot R12 is put at half course.
b) The directional coupler detector is adjusted in order to obtain the reading in the meter and
directivity.
c) R20 is adjusted till we obtain video 1Vpp in the oscilloscope that is terminated in 75 Ohm.
d) R35 is adjusted to 0Vdc in the blanking level.
e) Through R2, the video linearity is adjusted.
f ) Through L2 and R18, the filter is syntonized for 4.5 MHz minimum value over the video.