CTC 156/157 any good?

[N9ZQA]

I recently 'inherited' a RCA Colortrak from a relative and have been playing around with it in an attempt to learn something about 'modern' sets - my most modern set before this is a 1978 CCII.

It's an interesting set, with a decent audio section; an oval speaker on each side of the screen. The power cord isn't attached to the chassis, but is connected through an IEC C17 connector (similar to the power cord on a computer, but without a ground connection). The front panel indicates that it's a 'stereo monitor' - it has an AV input on the back.

It's seen a lot of on-time; it'll be of legal drinking age this September. I'm trying to figure out if the tube is tired or if there is another component problem. The picture is somewhat dark at the factory presets, but is watchable (with somewhat low contrast) if the brightness is turned up to about 75%. The on-screen display doesn't seem to change much in brightness when I do this (it looks dim all the time).

The focus is a compromise between the center and outer edges, and the edge convergence is slightly off until the set warms up. I tried to do a greyscale setup on it, but it doesn't have a service switch that I could see. Did the best I could by eye with a full raster but still about the same. I tried to cook the filaments for a while with a higher voltage, but no improvement. It's an A66 series tube; I've heard of some issues with them especially in mid-90's Zeniths.

Is this set worth doing anything with? I don't have a CRT tester, so no way at the moment to get an objective evaluation of its health, but the cabinet is in okay shape and I might like to use this one as a watcher for a while. If the tube is indeed weak, do these respond to rejuvenation (assuming I can find a rejuvenator that will work on a tube this new)?

-Jim