Round CRT arcing problem - Videokarma.org TV - Video

Chad Hauris · #1 05-19-2003, 08:22 AM

This weekend I got a Wards Airline round color TV at an estate sale, $5. It is an RCA CTC-15 clone. After I got the chassis operating, I noticed the CRT filaments were not lit and the CRT was arcing in the neck. I replaced the CRT with a 21FJP22 from another set, and the filaments lit up, but this time there is arcing from the CRT bulb to the mounting bracket. I replaced the HV anode lead, the 6BK4 plate lead, the 6BK4 tube, checked the 6BK4 cathode current to make sure the regulator is operating, and made sure the CRT was grounded to the chassis by alligator clips to the ground spring and also aluminum foil taped to the outside of the CRT. It is still arcing, though. Any ideas? Also, do you think the original CRT was destroyed by arcing (since it was arcing in the tube neck and filaments were dead). I can not find any evidence of cracks in the old tube.

kc8adu · #2 05-19-2003, 07:53 PM

the dag must be grounded and the bezel,brackets,and purity sheild must be all tied together to chassis ground.
i doubt this did in the old tube.is the dag(black coating)ok?
i have seen it peel off of a few tubes.

Chad Hauris · #3 05-20-2003, 06:52 AM

Thanks for the suggestions---I got it going o.k. by cleaning the aquadag coating (it is intact) and adding an additional grounding spring to the CRT purity shield, so there is a spring on top and botttom, and connecting the wires that I attatched to both of the springs to the HV cage chassis. The set had no CRT grounding wires attatched when I bought it. Also had arcing from the HV filament leads to the chassis---used a plastic insulator to move the leads away from the chassis.

kc8adu · #4 05-20-2003, 05:53 PM

that fil winding must be replaced if arcing.
easy to do and the 40kv wire is cheap at mcm.

Rob · #5 05-20-2003, 09:11 PM

Chad,

Glad you found the trouble. I had a funny problem in my RCA CTC-20. Even though the aquadag and demag shields were all properly grounded there was some very strange and scarry HV sparking going on. I was watching the convergence board with it flipped up to adjust while looking at the front of the set and bright, very intense blue HV sparks were happening in it. Glad I wasn't trying to adjust it at the time! It turns out a pinhole halfway up the white low density polyethelyne 3A3 socket well was allowing the HV, (a direct connection though a bit of wire inductance to the inner plate of the big capacitor we call the 21FJP22) to flash to earth ground at the flip cover of the doghouse in which the 3A3 socket is mounted. The rapid dV/dT was causing a very high voltage to be induced elsewhere in the convergence circuitry.

I was able to repair the 3A3 socket as god as new with a soldering iron and melting in some white LDPE from a plastic food container. It is a forever and very electrically sound repair. A previous 'hack' had gooped the whole area with white RTV bathtub caulking which doesn't even stick to polyethelyne, providing a repair with apparently short lived results.

Can you post some pictures of your new toy? We'd all love to see it!!!!!

Rob