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2-30 Line Transformer Removal/Replacement
1.
2.
3.
.4.
5.
6.
7.
8.
9.
10.
Tilt the 3720A onto its right hand side.
Remove the top and bottom covers from the
instru ment.
Release the two screws holding A20 in place
and lift out A20.
Remove the back panel high voltage cover.
Remove the internal high voltage cover.
Unplug the five wires from A17 and then
remove A I 7.
Remove XA20 mounting plate and pull it
gently to the side.
Note the wire colours against the corres-
ponding pin numbers on the top and bottom
of the line transformer and then unsolder
the connections.
Remove the four screws holding the trans-
former in position. Retain the underside
nuts and safety mouldings and pull the trans-
former out through the top of the instrument.
Re-assembly is a reversal of the above pro-
cedu re.
2-31 Chassis Mounted Transistors Plate
Removal/Replacement
1.
2.
3.
4.
5.
6.
7.
Remove the top cover and right side cover
from the instrument.
Release the two screws securing the A12/
A16 retaining strip and lift this strip clear.
Remove assemblies A12 to A16 inclusive.
Release the two screws a t the bottom of the
transistor plate.
Withdraw the plate.
Renew the faulty transistors as necessary.
Re-assembly is a reversal of the above pro-
cedu re.
2-32 High Voltage Tripler Assembly Removal/
Replacement
1.
Remove the top cover from the instrument.
2.
3.
4.
5.
6.
1 .
8.
9.
10:
11.
12.
13.
14.
15.
Section I1
Remove the internal high voltage cover.
Remove the rear panel high voltage cover.
Unplug the five wires from A17 and then
remove A1 7.
Unsolder the black and grey wires from the
ground tag.
Release the two screws holding A20 in place
and lift out A20.
Remove XA20 mounting plate.
Release the two screws securing the A l / A l l
retaining strip and lift this strip clear.
Remove assemblies A2 to A6 inclusive.
Remove A20 support block. Two screws
hold it in place.
Remove the two screws holding the high
voltage connector A55J1 in place. Disconnect
the flexible wiring from this connector.
Unsolder the wires
from XA(20(L) and
XA20(N) after noting their colours.
Remove the wires from the grommet.
Lift out the high voltage tripler assembly.
Re-assembly is a reversal of the above pro-
cedu re.
2-33 REPAIR PROCEDURES
2-34 Etched Circuits
2-35The etched circuit boards in the Spectrum
Display are of the plated-through type, consisting
of metallic conductors bonded to both sides of the
insulating material. The metallic conductors are
extended through the component mounting holes
by a plating process. Solder connection can be
made from either side of the board with equally
good results. Following are recommendations and
precautions pertinent to etched circuit repair
work
:
a.
Avoid unnecessary component substitution;
it can result in damage to the circuit board and/or
adjacent components.
2-5
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