Zenith L1846R ( Questions, questions... )

[RitchieMars]

Hey, I thought I'd drop by and make a more formal thread for the Zenith I mentioned in my introduction thread. After my initial tinkering, I've found that I have more questions than answers at this point. To be honest, I would like to do the repairs myself, perhaps within the next few months as time and funds permit, but if not I might find someone locally to service it for me. ( though I fear that would be expensive and probably more trouble than the tv is worth )

So here's the overall situation: The tv was said to have worked ( in the recent past ) and was hooked up to cable. ( Let's assume it was running and watchable within the past 2 years, although that doesn't mean much ) After some time of being stored and moved around, it no longer emits any sound and only produced a thin gray line across the screen. A very DIM gray line. This is as it was the day I bought it.

Since then, the only thing I've done ( since I haven't gotten ahold of a service manual ) is take the chassis out, clean all the dust out of it, clean the glass cover over the picture frame, and polish up the wood cabinet and put it back together. It seemed to continue to behave the same until I adjusted the "height" and got a larger picture, although it had two hard dark spots in the bottom corners. I was able to somewhat view a movie I had playing on a VCR, but the image was overlapping and distorted and after awhile I noticed everything was a bunch of horizontal streaks again. Not sure what I turned to get it that way.

Recently, I discovered that the thin metal rings around the CRT's neck were used to focus and adjust the picture. Also there was this little silver box on a tight metal clamp which can be adjusted in the same way, though it's towards the back of the neck and adjusting it helped the picture considerably. I believe these are called ion traps? I got a picture that grew quickly as the tv warmed up, from a perfectly squared rectangle which would fill the whole screen nicely minus the very bottom edge. The bottom edge is brighter than the rest and past that there's a about an inch of darkness. This changes somewhat when you adjust the picture with the height, linearity knobs and so forth, but still not quite a working picture.

Also, for some reason, the picture changes slightly as I turn the volume dial...? There is no audio coming from the set, so I wonder if there's some correlation.

I've only run the tv for about 15 minutes or so at a time, but I've come to the point of not turning it on at all since I figure I have a lot of work that needs to be done. Nothing in there ever smelled or appeared burnt, although the low voltage rectifier tube (5U4G) would often be pretty hot. Anyways, there's a few things I'm trying to figure out before I even think about buying capacitors and other parts for it.

(1) For one, is an extremely dim picture like this a definite sign of a bad CRT? There's a great deal of this aquadag stuff peeling off in places, and the black insulation around the yoke did fall apart... I mean, obviously the television likely needs capacitors, resistors, and maybe a few tubes BUT working in the manner that I've described, is a dim picture possible as a result of one of these smaller components failing? OR... should the picture still have brightness regardless and be indicative of a worn out CRT.

(2) If it IS bad, where in the world would I find a replacement 17'' CRT for a Zenith tv that's probably been out of production twice as long as I've been alive? Or could this one be saved?

(3) And something relatively unimportant at this point that continues to baffle me... can anyone please explain or point me to a website that explains the functionality of the picture adjustment controls? I see the vertical height, the horizontal and vertical hold and what those are doing, but things like... vertical range, and vertical linearity baffle me, as do these unlabeled knobs next to the word "screen." One turns, does something? and the other one makes the screen eventually turn gray with no contrast. There's also the fringe lock knob in the back. I can find nowhere on the internet thus far that explains these adjustments and what they do specifically.

Many thanks to anyone in advance who can shed some light on this.