Cathode Ray Tube

Use care when handling a crt. Breakage of the crt may cause high-velocity scattering of glass fragments (implosion). Protective clothing and safety glasses should be worn. Avoid striking the crt on any object which may cause it to crack or implode. When storing a crt, either place it in a protective carton or set it face down on a smooth surface in a protected location with a soft mat under the faceplate.

To remove the crt, perform the following steps:

1. Disconnect four deflection-plate wires at the middle of the crt neck and unplug the Trace Rotation connector (P8006) from the Front-Panel circuit board (note the connection locations and wire color for reinstallation reference).


The crt anode and output terminal of the High-Voltage Multiplier will retain a high-voltage charge after the instrument is turned off. To avoid electrical shock, ground both the output terminal of the multiplier and the crt high-voltage anode lead to the main instrument chassis after disconnecting the high-voltage lead.

2. Unplug the crt anode lead connector from the HighVoltage Multiplier at the front left corner of the High-Voltage shield and discharge it to the chassis.

3. Remove two screws that retain the plastic crt frame and light filter to the front panel. Remove the crt frame and light filter from the instrument.

3a. For Instruments with the Preregulator board (A18), remove two nuts securing the shield at the back of the crt and remove the shield.

4. With the rear of the instrument facing you, place the fingers of both hands over the front edge of the front subpanel. Then, using both thumbs, press forward gently on the crt funnel near the front of the crt. When the crt base pins disengage from the socket, remove the crt and crt shield through the instrument front subpanel. Place the crt in a safe place until it is ready to reinstall. If the plastic crt corner pads fall out, save them for reinstallation.

5. Remove the screw at the front upper left-hand corner and rotate the support bracket away from the High-Voltage shield.

5a. For instruments equipped with the Preregulator board (A18), remove the screw from the front of the HighVoltage Shield at the upper-left hand corner.

To reinstall the crt, perform the following steps:

5. Reinstall any plastic crt corner pads that may be out of place. Insert the crt, crt shield, anode lead, and Trace Rotation leads through the front-panel opening. Make sure all pins are straight and that the indexing keys on the crt base and socket are aligned. Make sure the crt shield ground clip only makes contact with the outside of the crt shield.

6. Push the crt base into the socket. Check that they are flush together as viewed from the rear and that the crt is seated properly in its front-panel opening.

6a. If applicable, reinstall the shield at the back of the crt; then secure it with two nuts (removed in step 3a).

7. Reinstall the crt frame and light filter; then secure them with two screws (removed in step 3).

8. Reconnect the crt anode lead to the High-Voltage Multiplier (disconnected in step 2).

9. Reconnect the four deflection-plate wires and the Trace Rotation connection (disconnected in step 1).

Was this article helpful?

+1 0

Post a comment