| CAUTION No modification of any circuit should be attempted. Service work should be performed only after you are thoroughly familiar with all of the following safety checks and service guidelines. To do otherwise in- creases the risk of potential hazards and injury to the user. SAFETY CHECKS Subject: Fire and Shock Hazard 1. Do not install, remove, or handle the picture tube in any manner unless shatter-proof goggles are worn. People not so equipped should be kept away while picture tubes are handled. Keep the picture tube away from the body while handling. 2. When service is required, observe the original lead dress. Extra precaution should be given to assure correct lead dress in the high voltage circuitry area. Where a short circuit has occurred, replace those components that indicate evidence of overheating. Always use the manufacturer's specified replace- ment component. See parts list in the back of this manual. 3. Periodically check the high voltage for proper value (14.5 KV + 5% at 0 beam current) using a meter of known accuracy and calibration. 4. To prevent fire or shock hazard DO NOT EXPOSE THIS DISPLAY TO RAIN OR MOISTURE. 5. Check for frayed insulation on wires. 1. Apply a suitable power and signal source to the deflection PCB P299 by means of input connector P100. (Refer to Assembly View Diagram, page 21) 2. Brightness and Contrast These controls are preset at the factory, but may be adjusted to suit program material. They are located on the right hand edge of the deflection amplifier PCB R517 is the brightness control and R514 is the contrast control. Both are finger adjustment con- trols. Caution must be exercised when adjusting the brightness coritrol. This control has more than 100% brightness range on most tubes. This control should be maintained below the point where a center spot appears on the CRT under normal input signal condition. Adjusting the control above this point may result in phosphor burn. 3. Spot Killer Indicator A spot killer circuit is used to blank the CRT under a no signal condition. When the spot killer is active, the CRT will be extinguished and LED D504 will light indicating spot killer operation. |
Work on these models should only be performed by those who are thoroughly familiar with precautions necessary when working on high voltage eguipment. Exercise care when servicing this chassis with power ap- plied. Many B plus and high voltage RF terminals are ex- posed which, if carelessly contacted can cause serious shock or result in damage to the chassis. Maintain inter- connecting ground lead connections between chassis and picture tube dag when operating chassis. Certain HV failures can increase X-ray radiation. Units should not be operated with HV levels exceeding the specified rating for their chassis type. The maximum operating HV specified for the chassis used in these units is 14.5KV + 500V at zero beam current with input voltage of 60 VAC + 10%. Higher voltage may also in- crease possibility of failure in HV supply. It is important to maintain specified values of all com- ponents in the high voltage circuits and anywhere else that could cause a rise in high voltage or operating supp- ly voltages. Refer to the Parts List and use ONLY exact replacement parts; especially picture tubes, semiconduc- tor devices, transformers, coils, fuses. To determine the presence of high voltage, use an ac- curate high impedance HV meter connected between se- cond anode lead and metal chassis frame only. When servicing the High Voltage System, remove static charge from it by connecting a 10K Ohm resistor in series with an insulated wire (such as a test probe) between picture tube dag and 2nd anode lead. (Input plug disconnected from chassis). The picture tube used in this display unit employs in- tegral implosion protection. Replace with tube of the same type number for continued safety. Do not lift pic- ture tube by the neck. Handle the picture tube only when wearing shatterproof goggles and after discharging the high voltage completely. Keep others without shatter- proof goggles away. Before returning the display to user, perform the follow- ing safety checks: 1. Inspect all lead dress to make certain that leads are not pinched or that hardware is not lodged between the chassis and other metal parts in the display. 2. Replace all protective devices such as non-metallic control knobs, insulating fishpapers, adjustment and compartment covers or shields. 3. To be sure that no shock hazard exists, a check for the presence of leakage current should be made at each exposed metal part. |