Quote:
Originally Posted by Electronic M
Unless you have a special HV probe designed to allow your DMM to measure up to at least 20KV don't try measuring your HV with a DMM.
Ways to measure approximate HV level without a DMM include taking an insulated screwdriver with a grounded blade and seeing how long of an ARC you can draw between the CRT bell and screwdriver. It should be in the 1/4"-1/2" range. You can check if the flyback is being driven properly by the output by holding a CFL light bulb or neon indicator lamp close to the flyback and the plate leads of the H output tube and HV rect while the set is warmed up and running....If the flyback is being driven properly the unconnected bulb will illuminate within an inch or 2 of those parts as a result of the RF harmonics of the sweep frequency being radiated.
If the first test fails but the second test passes the problem is either the HV rectifier, doorknob cap (they can fail, but about half the time are fine), resistors on the base of the rectifier or HV rect filament winding.
I check doorknob capacitors by disconnecting what ever end is easiest and placing the bottom of the rectifier (and cap if still attached to the rect) in a glass jar or dish so it can't arc to chassis, etc.
Definitely follow Dave's advice first before going into the weeds I've paid out above.  |
I checked the ion trap, put it in both ways, still nothing...
Checked the resistors under the 1B3, the 470K is good, but the 2.7 ohm is reading 5.7...Not sure if that would matter?
Removed the doorknob cap, it's 500PF at 20,000 volts.
Can I test it like it is, or will it fry my multimeter?
Wonder if I could bypass that cap and run the set to see if I get a picture, or is that crazy?