Hi,
After replacing the HOT and doing power up check, its usual to put in series a lamp bulb to limit the current. The problem comes after the lamp bulb is removed and full working voltage is fed to the circuit.
There is the possibility of HOT damaged instantly via HV secondary breakdown if there is some remaining fault in the rest of the circuit. As I understand from surfing the net, the HOT is usually operates at some 80% of its highest breakdown voltage Vceo.
I was wondering is it possible to put in parallel a string of varistors (or a series of neon bulbs with voltage grading resistors) from HOT collector to 0V so as to act as HV protection during the final test. After the max. coillector flyback pulse amplitute have been measured and confirmed using a 100:1 probe, the varistors can be removed.
In addition, if I can build a device which impose a fixed(settable) voltage drop with current limit, would it be possible to use it in series with the horizontal B+ to bring up the voltage to the Horiz. stage gradually?
Thanks in advance for your reply.
Regards
L.Chung