Quote:
Originally Posted by miniman82
Classic symptom of 3.58 oscillator drifting, you get rainbow bars. Phil is intimately aware of this problem.
There can be 3 reasons why this happens:
1. the crystal is going out, and the reactance tube can't pull it in to lock solid
2. a problem with the oscillator circuit itself (try twiddling the frequency coil near the tube)
3. alignment is so far off that the 3.58 information contained in the signal is too weak for the set to lock on to
Of course check the tubes, but you'll likely find a bad crystal or the oscillator coil out of whack. When you tweak the coil, you have to ground the signal coming from the phase detector or it'll just wander all over the place. You should see the rainbow bars float by slower and slower then they will lock in. Right before it locks, you'll notice the number of bars is getting smaller and smaller as the frequency gets closer and closer to being right.
|
I'll add solder joints to that list. On my Silvertone CTC15 clone it would come on good then within a minute go to looking like those screen shots above and soon after go to a monochrome picture with all saturated color elements displaying as green. After running for half an hour normal color would pop in. I lived with it for about a year before a PS cap I had already replaced once failed. While I was in there to fix that I resoldered all the chroma reference osc. traces on the board...After that(and a tweak to the osc. coil slug) the color synch has been ROCK solid.