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Section I1
2-30 Line Transformer Removal/Replacement 1. 2. 3. Tilt the 3720A onto its right hand side. Remove the top and bottom covers from the instrument. 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.
2. 3.
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.
4.
5. 6.
1.
.4.
5.
6. 7.
Unplug the five wires from A17 and then remove A I 7. Remove XA20 mounting plate and pull it gently to the side. ponding pin numbers on the top and bottom of the line transformer and then unsolder the connections.
8.
9.
Remove assemblies A2 to A6 inclusive.
8. Note the wire colours against the corres-
10: Remove A20 support block. Two screws hold it in place.
11. Remove the two screws holding the high voltage connector A55J1 in place. Disconnect the flexible wiring from this connector.
12. Unsolder the wires from XA(20(L) and XA20(N) after noting their colours. 13. Remove the wires from the grommet. 14. Lift out the high voltage tripler assembly. 15. Re-assembly is a reversal of the above procedu re. 2-33 REPAIR PROCEDURES
9.
Remove the four screws holding the transformer in position. Retain the underside nuts and safety mouldings and pull the transformer out through the top of the instrument.
10. Re-assembly is a reversal of the above procedure. 2-31 Chassis Mounted Transistors Plate Removal/Replacement 1. 2. 3. 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.
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
Remove assemblies A12 to A16 inclusive. transistor plate.
4. Release the two screws a t the bottom of the
5. 6. 7. Withdraw the plate. Renew the faulty transistors as necessary. Re-assembly is a reversal of the above procedure. 2-32 High Voltage Tripler Assembly Removal/ Replacement
