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HVJ-8718-19/FE HE RECEIVER
MAINTENANCE
1.
Deenergize the receiver.
Remove PCB A4A7.
2.
Remove the front panel and gently pull it out several
inches from the receiver main chassis, being careful not
to place any strain on the interconnecting cables.
3.
Connect the Oscilloscope Vertical input to connector J4-
1 using a short coaxial cable with clip leads on one
end.
Connect cable shield to ground.
Plug in headset
or a test speaker (optional).
4.
Connect the Signal Generator AM Output to terminal
A1-B57 using a short coaxial cable with clip leads on
one end.
Connect cable shield to terminal ground. Set
the Signal Generator Modulation Frequency to 400 Hz,
set Audio Output Level to 70 mV.
5.
Energize the receiver.
Select any detection mode and
rotate the Phone Level control fully
clockwise.
The
Oscilloscope should display a level of >20 V p-p. The
waveform should be a clean sine wave.
6.
Move the Oscilloscope input lead to connector J4-2.
The Oscilloscope should display a level of >20 V p-p.
The waveform should be a clean sine wave.
7.
If the signals are defective, replace 01, then R7.
8.
Deenergize the receiver and disconnect test equipment.
4.3.5
PARTS REPLACEMENT GOIDELINES
This paragraph provides techniques to assist the Technician
in replacing components on PC boards.
WARNING
To prevent electrical shock or damage to the
receiver, always disconnect the receiver from the
ac power source before soldering or replacing
components.
4.3.5.1
Soldering Techniques
When removing components from a printed circuit board for inspection or
replacement, be especially careful not to damage the track. The soldering iron power
should be no larger than 40 W, and a solder sipper or wieking procedure should be
employed when removing solder.
Non-corrosive soldering flux should be used when
removing solder by wieking.
In returning components to the board, make sure that
holes are clear and that leads do not catch the edge of the track and lift it from the
board. A good grade of rosin core 60/40 solder should be used. Heat no longer than
is necessary to achieve a good joint. A heat sink should be used where possible.
4-57
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