zenith comvergence jittery

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mcollinstn's picture
zenith comvergence jittery

An older 50" crt Zenith rear projector.

 Menu only allows moving red and blue centerpoints. No external way to adjust rotation of the guns, focus, or image scale.

My red and blue guns are very slightly out of rotation w the green, but I can live with that. My problem is that my red gun has intermittent problems with reduced image height. Can adjust center, but at extreme top and bottom of image, the red is a half inch "short". Vertical scale is the main issue, as horizontal doesn't appear to be off, or at least not much.

The red vertical "size" is not steady very well either. Sometimes is a bit jittery, but only noticeable when the image is steady. Also, there are times that the red is almost "correct" and is very close to the same scale as the blue and green. None are perfect at any given time, but the red issue is an "image killer".

I can solder, and I am a pretty quick study, have a nice Fluke with accessories and a steady hand. I just don't know where to start, and hate the thought of wrestling this booger back up 2 flights of stairs to take it somewhere to let the tech rape me.

 Any comments welcome.


Larry Dillon
Larry Dillon's picture
Mike, your set is

Mike, your set is experiencing a breakdown of the convergence IC.  They are getting worse as time goes on.  In a Zenith they call this the registration module.  If you get a model number and go to a Zenith authorized parts dealer, They still may have the complete module available.  If they do not, ptscorp.com will have this rebuilt modula available, or will rebuild your for you.  You can replace the IC,s yourself if you know how to work on solid state printed circuit boardsboards , but make sure you dont use any substandard cheap replacement parts, and also use plenty of heat sink compound on the back of the IC's before you install the new ones.  Then you will most likly need a service manual to do touch up convergence alighnment.  Now I could be all wet and there is simply a bad solder connection somewhere on the convergence board such as on the plugs on the board or on the convergence amp. IC's.  good Luck, and let us know how you make out with this set.


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