Remove the CRT card from ther CRT. Ground the G2 pin with jumper clips. Connect the focus pin to a screwdriver shaft. Apply power momentarily to get the HV up. Unplug the power and quickly touch the screwdriver to the CRT anode. Discharging the HV from Focus to G2 often removes internal shorts.
Clearing CRT Shorts - submitted by Jim Kocmoud. Jim is a member of our email discussion groups. All subscribers have access to his, as well as over one hundred other technician's comments and expertise.
If the CRT is shorted Focus to G2, one technique that we use is to disconnect the G2 wire from the CRT PCB. Then, power up the set, and when the focus voltage backfeeds into the G2 and builds up a potential, it will arc thru the G2 circuit protector to ground and Voila, short is gone! If the CRT is shorted HV to Focus, we remove the CRT PCB, and hold a grounded screwdriver about 1/2" away from the focus pin. Again, after power up, the resulting arc usually clears the short.
HK shorts in CRT's - submitted by Nicolas Cannonne. Nicolas is a member of our email discussion groups. All subscribers have access to his, as well as over one hundred other technician's comments and expertise.
This is useful when you have a CRT short from any cathode to heater. The aim is to apply an ungrounded voltage to heater pins. First cut all traces that goes to the heater pins on CRT board. Then take a wire, make one (or more) loop around FBT core and apply the 2 ends of the wire at the enter of the schema. This signal is something like AC signal going from –10V to +15V at the Horizontal frequency rate. So the diodes avoid any negative voltage, the caps are doing a nice flat 15VDC and the regulator make the 6.3V required for the heater. The LM317 has to be mounted on heatsink. I have added one more diode in input just to drop 0.7V.The less the input is the less the reg heats. Connect to 2 output pins directly to the heater pins on CRT board. First thing to do is to check with your scope the output voltage of the wire looped on FBT, may be you’ll have to do some additional turns to increase voltage. You can replace the 1K resistor by a 5K pot to adjust the output voltage. Heater usually draws something like 1A. This has saved 3 Trinitron CRT for me.
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