Two neon lamps in series? - Videokarma.org TV - Video

frenchy · #1 08-06-2005, 12:27 PM

My CTC-10w has these two NE2 lamps in series under the chassis, grounded on one end and other end seems to connect to bunch of different places in the schematics - brightness control, blanking, focus. What are they for? When the set is in operation, they are NOT lighting. Should they be or not, or only under certain conditions?
Everything seems to be working on the set ok except having color problems (tuner will lock in color but it's just one color (purple) that can be changed in intensity, tint control has no effect. Someone said maybe my 3.58 oscillator is not running. But I can't tell from the schematics what if anything the neon lamps could have to do with that, or if they should actually be glowing, and when. Would like to clear that up before poking around elsewhere. thanks!
Frenchy

jroberts500 · #2 08-06-2005, 01:49 PM

There is a thread here somewhere that discusses that set-up. I read that some had 2 some had 1. Can't remember more but I am almost certain it was about the same chassis; ctc 10.

Don Lindsly · #3 08-06-2005, 02:26 PM

The neon bulbs are to limit the flyback pulse amplitude that drives the color, blanking and agc circuits. The pulse will not normally be enough to light the bulbs. It must be there or you would see other problems.

Make sure the hue control is good. Clean it out and look for change. The burst phase transformer will act like a hue control when the color circuit is working.

Grounding the color test point should cause floating color lines across the picture during a color broadcast. If it does, then adjust the color oscillator coil for the colors to barely float by. Remove the ground and adjust the burst phase transformer for proper color with the hue control in the center of range.

Whatever fails during the procedure will point to the trouble area.

Don

holmesuser01 · #4 08-06-2005, 02:42 PM

My CTC-10 also has these bulbs. They are on occasionally. The ones in my set are new (1980) With them disconnected, I seem to remember the color drifting in tints.

Pete Deksnis · #5 08-06-2005, 04:35 PM

Early CTC10 chassis had a single NE2 in the subject circuit that tended to fail from being overdriven, at least in the early CTC10 chassis with which i have some experience. Later CTC10 chassis used two lamps in series to distribute the load stress. Once I modified the early chassis with two lamps, I never had to replace another NE2. Interesting to hear the reports of the lamps not always glowing; although it was many years ago, as I recall they were always on in the set I had.

Pete

frenchy · #6 08-06-2005, 06:22 PM

ok so it sounds like even if they were bad or removed, I should still not see a totally inoperative tint control or total lack of color decoding because of it. I'll leave them alone and concentrate on the rest of the circuitry. Actually I have only looked at the lamps while the flyback fuse was removed for testing so they very well could be lighting under normal circumstances with the pic tube in operation. Thanks! Frenchy

holmesuser01 · #7 08-06-2005, 11:33 PM

My bulbs are off right now. I'm running a DVD of old TV shows instead of my usual Playstation games. Color looks decent ( show is BONANZA) I've got to work on this baby soon. The sound is getting more buzz than normal.